stop start DODGE RAM SRT-10 2006 Service Service Manual

3.4C CLUTCH CIRCUIT LEAKS IN THE VALVE BODY
Turn the ignition off to the lock position.
Remove the transmission oil pan per the Service Information.
Remove the valve body per the Service Information.
Check condition of the 4C accumulator springs.
Look for possible leak paths into the 4C clutch hydraulics circuit within the valve body.
Were any problems found?
Ye s>>
Repair as necessary.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21- TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No>>
Go To 4
4.AIR CHECK 4C CLUTCH CIRCUIT
Perform an air check on the 4C Clutch circuit per the Service Information.
Listen for proper 4C Clutch piston movement.
Were any problems found?
Ye s>>
Repair Internal transmission as necessary. Pay attention to the mechanical components related to the
4th clutch. A broken or weak return spring or a dislocated snap ring could cause this problem.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21- TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No>>
Replace the Transmission Solenoid/TRS Assembly per the service information. With the scan tool, per-
form Quick Learn.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21- TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
5.VERIFY PCM OPERATION
Perform eight learnable starts. A learnable start is defined as follows: Start engine. From a standstill, accelerate
lightly to 50 MPH, then brake lightly to a stop. Turn off engine.
With the scan tool, record Transmission CL VOL INDEX (CVI) for all clutches.
With the scan tool, perform a BATTERY DISCONNECT.
With the scan tool, read the CVI’s and compare them to the reading recorded before the BATTERY DISCONNECT.
Are any of the CVI’s less than 5 or are they different than before the batterydisconnect?
Ye s>>
Using the schematics as a guide, check the Powertrain Control Module (PCM)terminals for corrosion,
damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems
are found, replace the PCM per the Service Information. With the scan tool,perform QUICK LEARN.
Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST - VER 1. (Refer to 21- TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 45RFE/545RFE - STANDARD PROCEDURE)
No>>
Te s t C o m p l e t e .

Improper adjustments
Hydraulic malfunctions
Mechanical malfunctions
Electronic malfunctions
Diagnosis of these problems should always begin by checking the easily accessible variables: fluid level and con-
dition, gearshift cable adjustment. Then perform a road test to determineif the problem has been corrected or if
more diagnosis is necessary. If the problem persists after the preliminary tests and corrections are completed,
hydraulic pressure checks should be performed.
PRELIMINARY
Two basic procedures are required. One procedure for vehicles that are drivable and an alternate procedure for
disabled vehicles (will not back up or move forward).
VEHICLE IS DRIVABLE
1. Check for transmission fault codes using scan tool.
2. Check fluid level and condition.
3. Adjust gearshift cable if complaint was based on delayed, erratic, or harsh shifts.
4. Road test and note how transmission upshifts, downshifts, and engages.
5. Perform hydraulic pressure test if shift problems were noted during roadtest.
6. Perform air-pressure test to check clutch operation.
VEHICLE IS DISABLED
1. Check fluid level and condition.
2. Check for broken or disconnected gearshift cable.
3. Check for cracked, leaking cooler lines, or loose or missing pressure-port plugs.
4. Raise and support vehicle on safety stands, start engine, shift transmission into gear, and note following:
a. If propeller shaft turns but wheels do not, problem is with differentialor axle shafts.
b. If propeller shaft does not turn and transmission is noisy, stop engine.Remove oil pan, and check for debris.
If pan is clear, remove transmission and check for damaged driveplate, converter, oil pump, or input shaft.
c. If propeller shaft does not turn and transmission is not noisy, perform hydraulic-pressure test to determine if
problem is hydraulic or mechanical.
ROAD TESTING
Before road testing, be sure the fluid level and control cable adjustmentshave been checked and adjusted if nec-
essary. Verify that all diagnostic trouble codes have been resolved.
Observe engine performance during the road test. A poorly tuned engine will not allow accurate analysis of trans-
mission operation.
Operate the transmission in all gear ranges. Check for shift variations and engine flare which indicates slippage.
Note if shifts are harsh, spongy, delayed, early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means clutch, overrunning clutch, or line pressure problems.
A slipping clutch can often be determined by comparing which internal units are applied in the various gear ranges.
The Clutch Application charts provide a basis for analyzing road test results.
45RFE CLUTCH APPLICATION CHART

3.COMPARE SCAN TOOL GOVERNOR PRESSURE READING TO PRESSURE GAUGE READING
Turn the ignition off to the lock position.
Connect a 700 kPa (100 psi) Pressure Gauge to the Governor Pressure test port. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE - DIAGNOSIS AND TESTING)
Start the engine and allow the engine to idle.
Warm the transmission to a normal operating temperature above 43° C (110° F).
With the scan tool, read the Governor Pressure and compare the scan tool Governor Pressure reading to the Pres-
sure Gauge reading.
Does the scan tool Governor Pressure reading match the Pressure Gauge reading within 6.9 kPa (1
psi)?
Ye s>>
Go To 4
No>>
Go To 7
4.TRANSMISSION - INTERNAL DAMAGE
Turn the ignition off to the lock position.
Remove the transmission oil pan per the Service Information. (Refer to 21 -TRANSMISSION/TRANSAXLE/AUTO-
MATIC - 48RE/FLUID - STANDARD PROCEDURE)
Inspect the transmission oil pan for burnt oil and/or excessive debris.
Does the transmission contain burnt oil and/or excessive debris?
Ye s>>
Repair internal transmission as necessary. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC -
48RE - REMOVAL)
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (GAS). (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE - STANDARD PROCEDURE)
No>>
Go To 5
5.CHECK INTERNAL TRANSMISSION FOR A FLUID LEAK
Inspect the transmission for internal fluid leakage in the Valve Body or the Governor Pressure Solenoid. (Refer to 21
- TRANSMISSION/TRANSAXLE/AUTOMATIC - 48RE/VALVE BODY - REMOVAL)
Were there any problems found?
Ye s>>
Repair the internal transmission as necessary per the Service Information. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 48RE/VALVE BODY - REMOVAL)
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (GAS). (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE - STANDARD PROCEDURE)
No>>
Go To 6
6.VERIFY OPERATION - TEST DRIVE
Remove the pressure gauge from the transmission.
Install the transmission oil pan and refill the transmission per the Service Information. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 48RE/FLUID - STANDARD PROCEDURE)
With the scan tool, erase Engine DTCs.
Test drive the vehicle.
Be sure to stop the vehicle and move the gear selector into the park positionfor a minimum of 5 seconds at least
three times during the drive cycle.
With the scan tool, read Engine DTCs.
Did the DTC reset?
Ye s>>
Using the schematics as a guide, check the Powertrain Control Module (PCM)pins, terminals, and con-
nectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground
circuits. If no problems are found, replace and program the PCM per the Service Information. (Refer to

3.COMPARE SCAN TOOL GOVERNOR PRESSURE READING TO PRESSURE GAUGE READING
Turn the ignition off to the lock position.
Connect a 700 kPa (100 psi) Pressure Gauge to the Governor Pressure test port. (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE - DIAGNOSIS AND TESTING)
Start the engine and allow the engine to idle.
Warm the transmission to a normal operating temperature above 43° C (110° F).
With the scan tool, read the Governor Pressure and compare the scan tool Governor Pressure reading to the Pres-
sure Gauge reading.
Does the scan tool Governor Pressure reading match the Pressure Gauge reading within 6.9 kPa (1
psi)?
Ye s>>
Go To 4
No>>
Go To 7
4.TRANSMISSION - INTERNAL DAMAGE
Turn the ignition off to the lock position.
Remove the transmission oil pan per the Service Information. (Refer to 21 -TRANSMISSION/TRANSAXLE/AUTO-
MATIC - 48RE/FLUID - STANDARD PROCEDURE)
Inspect the transmission oil pan for burnt oil and/or excessive debris.
Does the transmission contain burnt oil and/or excessive debris?
Ye s>>
Repair internal transmission as necessary. (Refer to 21 - TRANSMISSION/TRANSAXLE/AUTOMATIC -
48RE - REMOVAL)
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE - STANDARD PROCEDURE)
No>>
Go To 5
5.CHECK INTERNAL TRANSMISSION FOR A FLUID LEAK
Inspect the transmission for internal fluid leakage in the Valve Body or the Governor Pressure Solenoid. (Refer to 21
- TRANSMISSION/TRANSAXLE/AUTOMATIC - 48RE/VALVE BODY - REMOVAL)
Were there any problems found?
Ye s>>
Repair the internal transmission as necessary per the Service Information. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 48RE/VALVE BODY - REMOVAL)
Perform RE TRANSMISSION VERIFICATION TEST VER - 1 (DIESEL). (Refer to 21 - TRANSMISSION/
TRANSAXLE/AUTOMATIC - 48RE - STANDARD PROCEDURE)
No>>
Go To 6
6.VERIFY OPERATION - TEST DRIVE
Remove the pressure gauge from the transmission.
Install the transmission oil pan and refill the transmission per the Service Information. (Refer to 21 - TRANSMIS-
SION/TRANSAXLE/AUTOMATIC - 48RE/FLUID - STANDARD PROCEDURE)
With the scan tool, erase Engine DTCs.
Test drive the vehicle.
Be sure to stop the vehicle and move the gear selector into the park positionfor a minimum of 5 seconds at least
three times during the drive cycle.
With the scan tool, read Engine DTCs.
Did the DTC reset?
Ye s>>
Using the schematics as a guide, check the Engine Control Module (ECM) pins, terminals, and connec-
tors for corrosion, damage, or terminal push out. Pay particular attentiontoallpowerandgroundcir-

pressure to the overdrive clutch during 3-4 upshifts, and when accelerating in fourth gear. The 3-4 accumulator
cushions overdrive clutch engagement to smooth 3-4 upshifts. The accumulator is charged at the same time as
apply pressure acts against the overdrive piston.
DIAGNOSIS AND TESTING
AUTOMATIC TRANSMISSION
Automatic transmission problems can be a result of poor engine performance, incorrect fluid level, incorrect linkage
or cable adjustment, band or hydraulic control pressure adjustments, hydraulic system malfunctions or electrical/
mechanical component malfunctions. Begin diagnosis by checking the easily accessible items such as: fluid level
and condition, linkage adjustments and electrical connections. A road test will determine if further diagnosis is nec-
essary.
PRELIMINARY
Two basic procedures are required. One procedure for vehicles that are drivable and an alternate procedure for
disabled vehicles (will not back up or move forward).
VEHICLE IS DRIVEABLE
1. Check for transmission fault codes using DRBscan tool.
2. Check fluid level and condition.
3. Adjust throttle and gearshift linkage if complaint was based on delayed, erratic, or harsh shifts.
4. Road test and note how transmission upshifts, downshifts, and engages.
5. Perform hydraulic pressure test if shift problems were noted during roadtest.
6. Perform air-pressure test to check clutch-band operation.
VEHICLE IS DISABLED
1. Check fluid level and condition.
2. Check for broken or disconnected gearshift or throttle linkage.
3. Check for cracked, leaking cooler lines, or loose or missing pressure-port plugs.
4. Raise and support vehicle on safety stands, start engine, shift transmission into gear, and note following:
a. If propeller shaft turns but wheels do not, problem is with differentialor axle shafts.
b. If propeller shaft does not turn and transmission is noisy, stop engine.Remove oil pan, and check for debris.
If pan is clear, remove transmission and check for damaged drive plate, converter, oil pump, or input shaft.
c. If propeller shaft does not turn and transmission is not noisy, perform hydraulic-pressure test to determine if
problem is hydraulic or mechanical.
ROAD TESTING
Before road testing, be sure the fluid level and control cable adjustmentshave been checked and adjusted if nec-
essary. Verify that diagnostic trouble codes have been resolved.
Observe engine performance during the road test. A poorly tuned engine will not allow accurate analysis of trans-
mission operation.
Operate the transmission in all gear ranges. Check for shift variations and engine flare which indicates slippage.
Note if shifts are harsh, spongy, delayed, early, or if part throttle downshifts are sensitive.
Slippage indicated by engine flare, usually means clutch, band or overrunning clutch problems. If the condition is
advanced, an overhaul will be necessary to restore normal operation.
A slipping clutch or band can often be determined by comparing which internal units are applied in the various gear
ranges. The Clutch and Band Application chart provides a basis for analyzing road test results.
Clutch and Band Application Chart

vehicle. If the leak occurs on left turns, hoist the left side of the vehicle. If the leak occurs on right turns, hoist
the right side of the vehicle. For hoisting recommendations (Refer to LUBRICATION & MAINTENANCE/HOIST-
ING - STANDARD PROCEDURE).
WATER LEAK DETECTION
To detect a water leak point-of-entry, do a water test and watch for water tracks or droplets forming on the inside of
the vehicle. If necessary, remove interior trim covers or panels to gain visual access to the leak area. If the hose
cannot be positioned without being held, have someone help do the water test.
Some water leaks must be tested for a considerable length of time to become apparent. When a leak appears, find
the highest point of the water track or drop. The highest point usually willshow the point of entry. After leak point
has been found, repair the leak and water test to verify that the leak has stopped.
Locating the entry point of water that is leaking into a cavity between panels can be difficult. The trapped water may
splash or run from the cavity, often at adistance from the entry point. Mostwater leaks of this type become appar-
ent after accelerating, stopping, turning, or when on an incline.
MIRROR INSPECTION METHOD
When a leak point area is visually obstructed, use a suitable mirror to gainvisual access. A mirror can also be used
to deflect light to a limited-access area to assist in locating a leak point.
BRIGHT LIGHT LEAK TEST METHOD
Some water leaks in the luggage compartment can be detected without water testing. Position the vehicle in a
brightly lit area. From inside the darkened luggage compartment inspect around seals and body seams. If neces-
sary, have a helper direct a drop light over the suspected leak areas aroundthe luggage compartment. If light is
visible through a normally sealed location, water could enter through theopening.
PRESSURIZED LEAK TEST METHOD
When a water leak into the passenger compartment cannot be detected by water testing, pressurize the passenger
compartment and soap test exterior ofthe vehicle. To pressurize the passenger compartment, close all doors and
windows, start engine, and set heater control to high blower in HEAT position. If engine can not be started, connect
a charger to the battery to ensure adequate voltage to the blower. With interior pressurized, apply dish detergent
solution to suspected leak area on the exterior of the vehicle. Apply detergent solution with spray device or soft
bristle brush. If soap bubbles occur at a body seam, joint, seal or gasket, the leak entry point could be at that
location.
WIND NOISE
Wind noise is the result of most air leaks. Air leaks can be caused by poor sealing, improper body component
alignment, body seam porosity, or missing plugs in the engine compartmentor door hinge pillar areas. All body
sealing points should be airtight in normal driving conditions. Moving sealing surfaces will not always seal airtight
under all conditions. At times, side glass or door seals will allow wind noise to be noticed in the passenger com-
partment during high cross winds. Over compensating on door or glass adjustments to stop wind noise that occurs
under severe conditions can cause premature seal wear and excessive closing or latching effort. After a repair pro-
cedure has been performed, test vehicle to verify noise has stopped beforereturning vehicle to use.
VISUAL INSPECTION BEFORE TESTS
Verify that floor and body plugs are in place and body components are aligned and sealed. If component alignment
or sealing is necessary, refer to the appropriate section of this group forproper procedures.
ROAD TESTING WIND NOISE
1. Drive the vehicle to verify the general location of the wind noise.
2. Apply 50 mm (2 in.) masking tape in 150 mm (6 in.) lengths along weatherstrips, weld seams or moldings. After
each length is applied, drive the vehicle. If noise goes away after a piece of tape is applied, remove tape, locate,
and repair defect.

1 - MECHANISM COVERS (2) 10 - MOTOR FASTENERS (3)
2 - RIGHT HAND GLASS GUIDE 11 - SUNROOF MOTOR/MODULE ASSEMBLY
3 - GLASS FASTENERS (4) 12 - ALIGNMENT HOLE
4 - GLASS ASSEMBLY 13 - TRIM RING
5 - DRAIN CHANNEL 14 - ASSEMBLY FASTENERS (8)
6 - SUNSHADE 15 - ALIGNMENT HOLE
7 - LEFT SUNROOF GLASS GUIDE 16 - WIND DEFLECTOR
8 - WIRE HARNESS 17 - GLASS GUIDE FOOT
9 - SUNROOF ASSEMBLY 18 - WIND DEFLECTOR STRAP SCREWS (2)
The power sunroof system allows the sunroof to be opened, closed or placed in the vent position electrically by
actuating a switch in the overhead console. The sunroof system receives battery feed through a fuse in the Power
Distribution Center (PDC). The sunroof will operate normally with the keyin any position while the Accessory Delay
system is active.
The sunroof glass panel tilts upward at the rear for ventilation and slidesrearward under the roof when open. The
panel seals flush with the roof in the closed position to eliminate wind noise. The sunroof includes a manual-sliding
sunshade to cover the deep-tinted glass panel.
In addition to the standard power sunroof operation, this vehicle offers several additional features. There is an
express (one-touch) opening and closing feature as well as Excessive Force Limitation (EFL). The EFL function
detects obstacles trapped between the glass and the vehicle roof during a closing motion. Upon sensing an obstacle
the EFL function will reverse direction of the glass to allow removal of theobstacle.
The main components of thepower sunroof system are:
The motor/module assembly
The power sunroof glass and frame assembly
The power sunroof switch
The manual-sliding sunshade
OPERATION
This vehicle has a vent, tilt and slide power sunroof system with express (one-touch) open and closing feature. The
sunroof system receives constant battery feed through a fuse in the Power Distribution Center (PDC). The sunroof
will operate normally with the key in any position while the Accessory Delay system is active. If the sunroof is mov-
ing when the key is turned to the START position (crank engine), all motionsstop until the key is released, then the
previously requested sunroof motion will resume. The sunroof will also complete a requested motion if the Acces-
sory Delay system goes inactivewhile the motion is in progress.
A combination push-button and rocker switch module mounted in the overhead console controls sunroof operation.
The sunroof switch is a rocker design with a push button in the center of the two halves of the rocker. Pressing the
rocker towards the front of the car commands the sunroof closed. Pressing the rocker towards the rear of the car
commands the sunroof open. Pressing the center push button commands the sunroof up into the vent position
(Rear of sunroof glass raises above the vehicle roof with glass still covering the sunroof opening). All switch com-
mands operate with the glass startingin any position. (Refer to 8 - ELECTRICAL/POWER TOP/SWITCH - OPER-
ATION) for additional information.
An electronic control system, integralto the motor/module assembly, provides the express open and close functions.
Pressing the
openorcloseend of the rocker switch moves the sunroof glass panel to the full open or fullclosed
position, respectively. During express closing, anytime an obstacle is detected in the way of the glass, the motor will
stop and reverse travel to avoid pinching an occupant’s finger, ice in the track, etc. This function is called Excessive
Force Limitation (EFL). There are two methods of overriding the EFL function.
1. When three EFL events occur without the glass being allowed to fully close, the next close attempt will only
move while the close switch is continuously actuated. This allows the sunrooftobeforcedclosedifmultipleclose
attempts fail.
2. If the sunroof close switch is continuously actuated during an EFL event, through the reversal, and during a two
second wait time, then continuing to hold the close switch will cause the roof to move towards close with the EFL
protection disabled. This allows the sunroof to be forced closed if it is known that a reversal will occur.
While in EFL override, the closing motion will cease if the sunroof switch is released at any time.

degree of vacuum possible (approximately -88 kPa (- 26 in. Hg) or greater) for 30 minutes, close all valves and
turn off vacuum pump. If the system failsto reach specified vacuum, the refrigerant system likely has a leak that
must be corrected. If the refrigerantsystem maintains specified vacuum for at least 30 minutes, start the vacuum
pump, open the suction and discharge valves. Then allow the system to evacuate an additional 10 minutes.
4. Close all valves. Turn off and disconnect the vacuum pump.
5. Charge the refrigerant system (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - STANDARD PRO-
CEDURE - REFRIGERANT SYSTEM CHARGE).
REFRIGERANT SYSTEM CHARGE
WARNING: Refer to the applicable warnings and cautions for this system before performing the following
operation (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - WARNINGS) and (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING - CAUTIONS). Failure to follow the warnings and cautions could result
in possible personal injury or death.
NOTE: Always refer to the Underhood HVAC Specification Label for the refrigerant fill specification of the
vehicle being serviced.
After all refrigerant system leaks have been repaired and the refrigerantsystem has been evacuated, a refrigerant
charge can be injected into the system. For the proper amount of the refrigerant charge, refer to the Underhood
HVAC Specification Label.
An R-134a refrigerant recovery/recycling/charging station that meets SAE Standard J2210 must be used to charge
the refrigerant system with R-134a refrigerant. Refer to the operating instructions supplied by the equipment man-
ufacturer for proper care and use of this equipment.
CHARGING PROCEDURE
CAUTION: A small amount of refrigerant oil is removed from the A/C system each time the refrigerant sys-
tem is recovered and evacuated. Before charging the A/C system, you MUST replenish any oil lost during
the recovery process. Refer the equipment manufacturer instructions formore information.
1. Evacuate the refrigerant system (Refer to 24 - HEATING & AIR CONDITIONING/PLUMBING - STANDARD PRO-
CEDURE - REFRIGERANT SYSTEM EVACUATE).
2. A manifold gauge set and an R-134a refrigerant recovery/recycling/charging station that meets SAE standard
J2210 should be connected to the refrigerant system.
3. Measure the proper amount of refrigerant and heat it to 52° C (125° F) withthe charging station. See the oper-
ating instructions supplied by the equipment manufacturer for proper useof this equipment.
4. Open both the suction and discharge valves, then open the charge valve toallow the heated refrigerant to flow
into the system.
5. When the transfer of refrigerant has stopped, close both the suction anddischarge valves.
6. If all of the refrigerant charge did not transfer from the dispensing device, open all of the windows in the vehicle
and set the heating-A/C system controls so that the A/C compressor is engaged and the blower motor is oper-
ating at its lowest speed setting. Run the engine at a steady high idle (about 1400 rpm). If the A/C compressor
does not engage, test the compressor clutch control circuit and repair as required.
7. Open the low-side valve to allow the remaining refrigerant to transfer to the refrigerant system.
WARNING: Take care not to open the discharge (high pressure) valve at this time. Failure to follow this
warning could result in possible personal injury or death.
8. Disconnect the charging station and manifold gauge set from the refrigerant system service ports.
9. Reinstall the caps onto the refrigerant system service ports.

The primary components within the assembly are: A three port solenoid thatactivates both of the functions listed
above; a pump which contains a switch, two check valves and a spring/diaphragm, a canister vent valve (CVV) seal
which contains a spring loaded vent seal valve.
Immediately after a cold start, between predetermined temperature thresholds limits, the three port solenoid is briefly
energized. This initializes the pump by drawing air into the pump cavity and also closes the vent seal. During non
test conditions the vent seal is held open by the pump diaphragm assembly which pushes it open at the full travel
position. The vent seal will remain closed while the pump is cycling due to the reed switch triggering of the three
port solenoid that prevents the diaphragm assembly from reaching full travel. After the brief initialization period, the
solenoid is de-energized allowing atmospheric pressure to enter the pumpcavity, thus permitting the spring to drive
the diaphragm which forces air out of the pump cavity and into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow in typical diaphragmpump fashion. The pump is controlled in
2 modes:
Pump Mode: The pump is cycled at a fixed rate to achieve a rapid pressure build in order to shorten the overall test
length.
Test Mode: The solenoid is energized with a fixed duration pulse. Subsequent fixed pulses occur when the dia-
phragm reaches the Switch closure point.
The spring in the pump is set so that the system will achieve an equalized pressure of about 7.5” H20. The cycle
rate of pump strokes is quite rapid as the system begins to pump up to this pressure. As the pressure increases, the
cycle rate starts to drop off. If there is no leak in the system, the pump would eventually stop pumping at the equal-
ized pressure. If there is a leak, it will continue to pump at a rate representative of the flow characteristic of the size
of the leak. From this information we can determine if the leak is larger than the required detection limit (currently
set at .040” orifice by CARB). If a leak is revealed during the leak test portion of the test, the test is terminated at
the end of the test mode and no further system checks will be performed.
After passing the leak detection phase of the test, system pressure is maintained by turning on the LDP’s solenoid
until the purge system is activated. Purge activation in effect creates a leak. The cycle rate is again interrogated and
when it increases due to the flow through the purge system, the leak check portion of the diagnostic is complete.
The canister vent valve will unseal the system after completion of the testsequence as the pump diaphragm assem-
bly moves to the full travel position.
Evaporative system functionality will be verified by using the stricter evap purge flow monitor. At an appropriate
warm idle the LDP will be energized to seal the canister vent. The purge flowwill be clocked up from some small
value in an attempt to see a shift in the02 control system. If fuel vapor, indicated by a shift in the 02 control, is
present the test is passed. If not, it is assumed that the purge system is notfunctioning in some respect. The LDP
is again turned off and the test is ended.
MISFIRE MONITOR
Excessive engine misfire results in increased catalyst temperature and causes an increase in HC emissions. Severe
misfires could cause catalyst damage. To prevent catalytic convertor damage, the PCM monitors engine misfire.
The Powertrain Control Module (PCM) monitors for misfire during most engine operating conditions (positive torque)
by looking at changes in the crankshaft speed. If a misfire occurs the speedof the crankshaft will vary more than
normal.
FUEL SYSTEM MONITOR
To comply with clean air regulations, vehicles are equipped with catalytic converters. These converters reduce the
emission of hydrocarbons, oxides of nitrogen and carbon monoxide. The catalyst works best when the Air Fuel (A/F)
ratio is at or near the optimum of 14.7 to 1.
The PCM is programmed to maintain the optimum air/fuel ratio of 14.7 to 1. This is done by making short term
corrections in the fuel injector pulse width based on the O2S sensor output. The programmed memory acts as a self
calibration tool that the engine controller uses to compensate for variations in engine specifications, sensor toler-
ances and engine fatigue over the life span of the engine. By monitoring theactual fuel-air ratio with the O2S sen-
sor (short term) and multiplying that with the program long-term (adaptive) memory and comparing that to the limit,
it can be determined whether it will pass an emissions test. If a malfunction occurs such that the PCM cannot main-
tain the optimum A/F ratio, then the MIL will be illuminated.

CATALYST MONITOR
To comply with clean air regulations, vehicles are equipped with catalytic converters. These converters reduce the
emission of hydrocarbons, oxides of nitrogen and carbon monoxide.
Normal vehicle miles or engine misfire can cause a catalyst to decay. This can increase vehicle emissions and
deteriorate engine performance, driveability and fuel economy.
The catalyst monitor uses dual oxygen sensors (O2S’s) to monitor the efficiency of the converter. The dual O2S’s
sensor strategy is based on the fact that as a catalyst deteriorates, its oxygen storage capacity and its efficiency are
both reduced. By monitoring the oxygen storage capacity of a catalyst, itsefficiency can be indirectly calculated. The
upstream O2S is used to detect the amount of oxygen in the exhaust gas beforethe gas enters the catalytic con-
verter. The PCM calculates the A/F mixture from the output of the O2S. A low voltage indicates high oxygen content
(lean mixture). A high voltage indicates a low content of oxygen (rich mixture).
When the upstream O2S detects a lean condition, there is an abundance of oxygen in the exhaust gas. A function-
ing converter would store this oxygen so it can use it for the oxidation of HCand CO. As the converter absorbs the
oxygen, there will be a lack of oxygen downstream of the converter. The output of the downstream O2S will indicate
limited activity in this condition.
As the converter loses the ability to store oxygen, the condition can be detected from the behavior of the down-
stream O2S. When the efficiency drops, no chemical reaction takes place. This means the concentration of oxygen
will be the same downstream as upstream. The output voltage of the downstream O2S copies the voltage of the
upstream sensor. The only difference is a time lag (seen by the PCM) betweenthe switching of the O2S’s.
To monitor the system, the number of lean-to-rich switches of upstream anddownstream O2S’s is counted. The
ratio of downstream switches to upstream switches is used to determine whether the catalyst is operating properly.
An effective catalyst will have fewer downstream switches than it has upstream switches i.e., a ratio closer to zero.
For a totally ineffective catalyst, this ratio will be one-to-one, indicating that no oxidation occurs in the device.
The system must be monitored so that when catalyst efficiency deteriorates and exhaust emissions increase to over
the legal limit, the MIL will be illuminated.
TRIP DEFINITION
The term “Trip” has different meanings depending on what the circumstances are. If the MIL (Malfunction Indicator
Lamp) is OFF, a Trip is defined as when the Oxygen Sensor Monitor and the Catalyst Monitor have been completed
in the same drive cycle.
When any Emission DTC is set, the MIL on the dash is turned ON. When the MIL is ON, it takes 3 good trips to turn
the MIL OFF. In this case, it depends on what type of DTC is set to know what a “Trip” is.
For the Fuel Monitor or Mis-Fire Monitor (continuous monitor), the vehicle must be operated in the “Similar Condition
Window” for a specified amount of time to be considered a Good Trip.
If a Non-Continuous OBDII Monitor fails twice in a row and turns ON the MIL, re-running that monitor which previ-
ously failed, on the next start-up and passing the monitor, is considered tobeaGoodTrip.Thesewillincludethe
following:
Oxygen Sensor
Catalyst Monitor
Purge Flow Monitor
Leak Detection Pump Monitor (if equipped)
EGR Monitor (if equipped)
Oxygen Sensor Heater Monitor
If any other Emission DTC is set (not an OBDII Monitor), a Good Trip is considered to be when the Oxygen Sensor
Monitor and Catalyst Monitor have been completed; or 2 Minutes of engine run time if the Oxygen Sensor Monitor
or Catalyst Monitor have been stopped from running.
It can take up to 2 Failures in a row to turn on the MIL. After the MIL is ON, it takes3GoodTripstoturntheMIL
OFF. After the MIL is OFF, the PCM will self-erase the DTC after 40 Warm-up cycles. A Warm-up cycle is counted
when the ECT (Engine Coolant Temperature Sensor) has crossed 160°F (71.1C) and has risen by at least 40°F
(4.4°C) since the engine has been started.