light CHEVROLET DYNASTY 1993 Service Manual

The PCM adjusts ignition timing based on the fol-
lowing inputs.
² engine coolant temperature
² engine speed (distributor pick-up)
² manifold absolute pressure
² throttle position
The Automatic Shut Down (ASD) and Fuel Pump
relays are mounted externally, but turned on and off
by the PCM through the same circuit. The distributor pick-up signal is sent to the PCM.
If the PCM does not receive a distributor signal
within approximately one second of engine cranking,
the ASD relay and fuel pump relay are deactivated.
When these relays are deactivated, power is shut off
to the fuel injector, ignition coil, oxygen sensor heat-
ing element and fuel pump. The PCM contains a voltage converter that
changes battery voltage to a regulated 8.0 volts. The
8.0 volts power the distributor pick-up and vehicle
speed sensor. The PCM also provides a 5.0 volts sup-
ply for the coolant temperature sensor, manifold ab-
solute pressure sensor and throttle position sensor.
AIR CONDITIONING SWITCH SENSE (AA, AG, AJ
BODY)ÐPCM INPUT
When the air conditioning or defrost switch is in
the ON position and the low pressure and high pres-
sure switches are closed, the PCM receives an input
for air conditioning. After receiving this input, the
PCM activates the A/C compressor clutch by ground-
ing the A/C clutch relay. The PCM also adjusts idle
speed to a scheduled RPM to compensate for in-
creased engine load.
AIR CONDITIONING SWITCH SENSE (AC
BODY)ÐPCM INPUT
When the air conditioning or defrost switch is in
the ON position and the low pressure, high pressure
and ambient temperature switches are closed, the
PCM receives an input for air conditioning. After re-
ceiving this input, the PCM activates the A/C com-
pressor clutch by grounding the A/C clutch relay.
The PCM also adjusts idle speed to a scheduled RPM
to compensate for increased engine load.
BATTERY VOLTAGEÐPCM INPUT
The PCM monitors the battery voltage input to de-
termine fuel injector pulse width and generator field
control. If battery voltage is low, the PCM will in-
crease injector pulse width.
BRAKE SWITCHÐPCM INPUT
When the brake switch is activated, the PCM re-
ceives an input indicating that the brakes are being
applied. After receiving this input the PCM main-
tains idle speed to a scheduled RPM through the idle
air control motor. The brake switch is mounted on
the brake pedal support bracket.
ENGINE COOLANT TEMPERATURE SENSORÐPCM
INPUT
The coolant temperature sensor is a variable resis-
tor with a range of -40É to 265É. The sensor is in-
stalled next to the thermostat housing. The PCM supplies 5.0 volts to the coolant temper-
ature sensor. The sensor provides an input voltage to
the PCM (Fig. 3). As coolant temperature varies, the
sensors resistance changes, resulting in a different
input voltage to the PCM. The PCM demands slightly richer air-fuel mixtures
and higher idle speeds until the engine reaches nor-
mal operating temperature. This sensor is also used for cooling fan control.
DISTRIBUTOR PICK-UPÐPCM INPUT
The distributor pick-up provides two inputs to the
PCM. From one input the PCM determines RPM (en-
gine speed). From the other input it derives crank-
shaft position. The PCM regulates injector
synchronization and adjusts ignition timing and en-
gine speed based on these inputs. The distributor pick-up contains two signal gener-
ators. The pick-up unit consists of 2 light emitting
diodes (LED), 2 photo diodes, and a separate timing
disk. The timing disk contains two sets of slots. Each
set of slots rotates between a light emitting diode
and a photo diode (Fig. 4). The inner set contains 6
large slots, one for each cylinder. The outer set con-
tains several smaller slots. The outer set of slots on the rotating disk repre-
sents 2 degrees of crankshaft rotation. Up to 1200
engine RPM, the PCM uses the input from the outer
set of slots to increase ignition timing accuracy. The outer set of slots contains a 10 degree flat spot
(Fig. 5). The flat spot tells the PCM that the next
piston at TDC will be number 6. The position of each
piston is referenced by one of the six inner slots (Fig.
5). As each slot on the timing disk passes between the
diodes, the beam from the light emitting diode is in-
Fig. 3 Coolant Temperature Sensor
Ä FUEL SYSTEMS 14 - 115

SYSTEM TESTS
WARNING: APPLY PARKING BRAKE AND/OR BLOCK
WHEELS BEFORE PERFORMING ANY TEST ON AN
OPERATING ENGINE.
OBTAINING DIAGNOSTIC TROUBLE CODES
(1) Connect DRBII scan tool to the data link connec-
tor located in the engine compartment near the pow-
ertrain control module (PCM). (2) Start the engine if possible, cycle the transaxle
selector and the A/Cswitch if applicable. Shut off the
engine. (3) Turn the ignition switch on, access Read Fault
Screen. Record all the fault messages shown on the
DRBII scan tool. Observe the malfunction indicator
lamp (Check Engine lamp on the instrument panel).
The lamp should light for 3 seconds then go out (bulb
check). Diagnostic trouble code erasure; access erase
diagnostic trouble code data
STATE DISPLAY TEST MODE
The switch inputs used by the powertrain control
module (PCM) have only two recognized states, HIGH
and LOW. For this reason, the PCM cannot recognize
the difference between a selected switch position ver-
sus an open circuit, a short circuit, or a defective
switch. If the change is displayed, it can be assumed
that the entire switch circuit to the PCM is functional.
From the state display screen access either State
Display Inputs and Outputs or State Display Sensors.
STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRBII scan tool to the vehicle. Access
the State Display screen. Then access Inputs and
Outputs. The following is a list of the engine control
system functions accessible through the Inputs and
Outputs screen. Park/Neutral Switch
Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
A/C Switch Sense
S/C Vent Solenoid
S/C Vacuum Solenoid
A/C Clutch Relay
EGR Solenoid
Auto Shutdown Relay
Radiator Fan Relay
Purge Solenoid
Torque Converter Clutch Solenoid
Malfunction Indicator Lamp (Check Engine Lamp)
STATE DISPLAY SENSORS
Connect the DRBII scan tool to the vehicle and ac-
cess the State Display screen. Then access Sensor
Display. The following is a list of the engine control
system functions accessible through the Sensor Dis-
play screen. Battery Temperature
Oxygen Sensor Signal
Engine Coolant Temperature
Engine Coolant Temp Sensor
Throttle Position
Minimum Throttle
Battery Voltage
MAP Sensor Reading
Idle Air Control Motor Position
Adaptive Fuel Factor
Barometric Pressure
Min Airflow Idle Speed
Engine Speed
Fault #1 Key-On Info
Module Spark Advance
Speed Control Target
Fault #2 Key-on Info
Fault #3 Key-on Info
Speed Control Status
Speed Control Switch Voltage
Charging System Goal
Theft Alarm Status
Map Sensor Voltage
Vehicle Speed
Oxygen Sensor State
MAP Gauge Reading
Throttle Opening (percentage)
Total Spark Advance
CIRCUIT ACTUATION TEST MODE
The circuit actuation test mode checks for proper
operation of output circuits or devices which the pow-
ertrain control module (PCM) cannot internally rec-
ognize. The PCM can attempt to activate these
outputs and allow an observer to verify proper oper-
ation. Most of the tests provide an audible or visual
indication of device operation (click of relay contacts,
spray fuel, etc.). Except for intermittent conditions, if
a device functions properly during testing, assume
the device, its associated wiring, and driver circuit
working correctly.
OBTAINING CIRCUIT ACTUATION TEST
Connect the DRBII scan tool to the vehicle and ac-
cess the Actuators screen. The following is a list of
the engine control system functions accessible
through Actuators screens. Stop All Tests
Ignition Coil #1
Fuel Injector #1
Fuel Injector #2
Fuel Injector #3
14 - 134 FUEL SYSTEMS Ä

HEATED OXYGEN SENSOR (O2SENSOR)
The oxygen sensor is installed in the exhaust man-
ifold (Fig. 21).
CAUTION: Do not pull on the oxygen sensor wires
when disconnecting the electrical connector. WARNING: THE EXHAUST MANIFOLD MAY BE EX-
TREMELY HOT. USE CARE WHEN SERVICING THE
OXYGEN SENSOR.
(1) Disconnect oxygen sensor electrical connector.
(2) Remove sensor using Tool C-4907 (Fig. 22).
Slightly tightening the sensor can ease removal.
When the sensor is removed, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E tap.
If using original sensor, coat the threads with Loctite
771-64 anti-seize compound or equivalent. New sen-
sors are packaged with compound on the threads and
do not require additional compound. The sensor must
be tightened to 27 N Im (20 ft. lbs.) torque.
Fig. 19 PCMÐAC Body
Fig. 20 PCMÐAG and AJ Bodies
Fig. 21 Heated Oxygen Sensor
Fig. 22 Oxygen Sensor Socket
14 - 144 FUEL SYSTEMS Ä

to low. The number of notches determine the amount of
pulses. If available, an oscilloscope can display the
square wave patterns of each timing events. Top dead center (TDC) does not occur when notches
on the camshaft sprocket pass below the cylinder. TDC
occurs after the camshaft pulse (or pulses) and after
the 4 crankshaft pulses associated with the particular
cylinder. The arrows and cylinder call outs on Figure 4
represent which cylinder the flat spot and notches
identify, they do not indicate TDC position. The camshaft position sensor is mounted to the top of
the timing case cover (Fig. 5). The bottom of the sensor
is positioned above the camshaft sprocket. The dis-
tance between the bottom of sensor and the
camshaft sprocket is critical to the operation of
the system. When servicing the camshaft posi-
tion sensor, refer to the 3.3L and 3.8L Multi-Port
Fuel InjectionÐService Procedures section in
this Group.
ENGINE COOLANT TEMPERATURE SENSORÐPCM
INPUT
The coolant temperature sensor is a variable resistor
with a range of -40ÉF to 265ÉF. The sensor is installed
next to the thermostat housing (Fig. 6). The PCM supplies 5.0 volts to the coolant tempera-
ture sensor. The sensor provides an input voltage to the
PCM. As coolant temperature varies, the sensor resis-
tance changes resulting in a different input voltage to
the PCM. When the engine is cold, the PCM will demand
slightly richer air-fuel mixtures and higher idle speeds
until normal operating temperatures are reached. The coolant sensor is also used for cooling fan control.
CRANKSHAFT POSITION SENSORÐPCM INPUT
The crankshaft position sensor (Fig. 7) senses slots cut
into the transaxle driveplate extension. There ar e a 3 sets
of slots. Each set contains 4 slots, for a total of 12 slots (Fig. 8). Basic timing is determined by the position of the
last slot in each group. Once the PCM senses the last slot,
it determines crankshaft position (which piston will next
be at TDC) from the camshaft position sensor input. The
4 pulses generated by the crankshaft position sensor
represent the 69É, 49É, 29É, and 9É BTDC marks. It may
take the PCM one engine revolution to determine crank-
shaft position during cranking.
The PCM uses the camshaft position sensor to deter-
mine injector sequence. The PCM determines igni-
Fig. 5 Camshaft Position Sensor Location
Fig. 6 Coolant Temperature Sensor
Fig. 7 Crankshaft Position Sensor
Fig. 8 Timing Slots
14 - 148 FUEL SYSTEMS Ä

line. However, these could result in a rich or lean
condition causing an oxygen sensor fault to be stored in
the PCM. Secondary Ignition Circuit - The PCM cannot
detect an inoperative ignition coil, fouled or worn spark
plugs, ignition cross firing, or open spark plug cables. Engine Timing - The PCM cannot detect an incor-
rectly indexed timing chain, camshaft sprocket and
crankshaft sprocket. However, these could result in a
rich or lean condition causing an oxygen sensor fault to
be stored in the PCM. Cylinder Compression - The PCM cannot detect
uneven, low, or high engine cylinder compression. Exhaust System - The PCM cannot detect a
plugged, restricted or leaking exhaust system. Fuel Injector Malfunctions - The PCM cannot
determine if a fuel injector is clogged, the needle is
sticking or the wrong injector is installed. However,
these could result in a rich or lean condition causing an
oxygen sensor fault to be stored in the PCM. Excessive Oil Consumption - Although the PCM
monitors exhaust stream oxygen content when the
system is in closed loop, it cannot determine excessive
oil consumption. Throttle Body Air Flow - The PCM cannot detect a
clogged or restricted air cleaner inlet or filter element. Evaporative System - The PCM will not detect a
restricted, plugged or loaded evaporative purge canis-
ter. Vacuum Assist - Leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices are not monitored by the PCM. How-
ever, these could result in a MAP sensor fault being
stored in the PCM. PCM System Ground - The PCM cannot determine
a poor system ground. However, a diagnostic trouble
code may be generated as a result of this condition. PCM Connector Engagement - The PCM cannot
determine spread or damaged connector pins. How-
ever, a diagnostic trouble code may be generated as a
result of this condition.
HIGH AND LOW LIMITS
The powertrain control module (PCM) compares in-
put signal voltages from each input device with estab-
lished high and low limits for the device. If the input
voltage is not within limits and other diagnostic
trouble code criteria are met, a diagnostic trouble code
will be stored in memory. Other diagnostic trouble code
criteria might include engine RPM limits or input
voltages from other sensors or switches that must be
present before a fault condition can be verified.
DIAGNOSTIC TROUBLE CODE DESCRIPTION
A diagnostic trouble code indicates that the power-
train control module (PCM) has recognized an abnor- mal condition in the system. Diagnostic trouble codes
can be obtained from the malfunction indicator lamp
(Check Engine lamp on the instrument panel) or from
the DRBII scan tool. Diagnostic trouble codes indicate
the results of a failure but do not identify the failed
component directly.
SYSTEM TESTS
WARNING: APPLY PARKING BRAKE AND/OR BLOCK
WHEELS BEFORE PERFORMING ANY TEST ON AN
OPERATING ENGINE.
OBTAINING DIAGNOSTIC TROUBLE CODES
(1) Connect the DRBII scan tool to the data link
connector located in the engine compartment near the
driver side strut tower (Fig. 1). (2) Start the engine if possible, cycle the transaxle
selector and the A/Cswitch if applicable. Shut off the
engine. (3) Turn the ignition switch on, access Read Fault
Screen. Record all the fault messages shown on the
DRBII scan tool. Observe the malfunction indicator
lamp (check engine lamp on the instrument panel). The
lamp should light for 2 seconds then go out (bulb
check). Diagnostic trouble code erasure; access erase
diagnostic trouble code data
STATE DISPLAY TEST MODE
The switch inputs used by the powertrain control
module (PCM) have only two recognized states, HIGH
and LOW. For this reason, the PCM cannot recognize
the difference between a selected switch position ver-
sus an open circuit, a short circuit, or a defective
switch. If the change is displayed, it can be assumed
that the entire switch circuit to the PCM is functional.
From the state display screen access either State
Display Inputs and Outputs or State Display Sensors.
STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRBII scan tool to the vehicle and access
the State Display screen. Then access Inputs and
Outputs. The following is a list of the engine control
system functions accessible through the Inputs and
Outputs screen. Park/Neutral Switch
Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
A/C Switch Sense
S/C Vent Solenoid
Ä FUEL SYSTEMS 14 - 163

(5) Reverse the above procedure for installation.
CRANKSHAFT POSITION SENSOR
REMOVAL
(1) Disconnect crankshaft position sensor electrical
connector from the wiring harness connector (Fig. 23).
(2) Remove crankshaft position sensor retaining
bolt. (3) Pull sensor straight up out of the transaxle
housing.
INSTALLATION
If installing the original sensor, clean off the
old spacer on the sensor face. A NEW SPACER
must be attached to the sensor face before instal-
lation. If the sensor is being replaced, confirm
that the paper spacer is attached to the face of
the new sensor (Fig. 24).
(1) Install sensor in transaxle and push sensor down
until contact is made with the drive plate. While
holding the sensor in this position, and install and
tighten the retaining bolt to 12 N Im (105 in. lbs.)
torque. (2) Connect crankshaft position sensor electrical
connector to the wiring harness connector.
CAMSHAFT POSITION SENSOR SERVICE
REMOVAL
(1) Disconnect camshaft position sensor electrical
connector from the wiring harness connector (Fig. 25).
(2) Loosen camshaft position sensor retaining bolt
enough to allow slot in sensor to slide past the bolt. (3) Pull sensor up out of the chain case cover. Do not
pull on the sensor lead. There is an O-ring on the
sensor case. The O-ring may make removal difficult. A
light tap to top of sensor prior to removal may reduce
force needed for removal.
INSTALLATION
If installing the original sensor, clean off the
old spacer on the sensor face. A NEW SPACER
must be attached to the face before installation.
Inspect O-ring for damage, replace if necessary.
If the sensor is being replaced, confirm that the
paper spacer is attached to the face and O-ring is
positioned in groove of the new sensor (Fig. 26).
(1) Apply a couple drops of clean engine oil to the
O-ring prior to installation. Install sensor in the chain
case cover and push sensor down until contact
Fig. 23 Crankshaft Position Sensor
Fig. 24 Crankshaft Position Sensor and Spacer
Fig. 25 Camshaft Position Sensor
Fig. 26 Camshaft Position Sensor
14 - 176 FUEL SYSTEMS Ä

is made with the camshaft gear. While holding the
sensor in this position, install and tighten the retain-
ing bolt 12 N Im (105 in. lbs.) torque.
(2) Connect camshaft position sensor electrical con-
nector to harness connector. Position connector away
from the accessory belt.
HEATED OXYGEN SENSOR (O2SENSOR) SERVICE
The oxygen sensor is installed in the exhaust mani-
fold (Fig. 27).
CAUTION: Do not pull on the oxygen sensor wire
when disconnecting the electrical connector.
WARNING: THE EXHAUST MANIFOLD MAY BE EX-
TREMELY HOT. USE CARE WHEN SERVICING THE
OXYGEN SENSOR.
(1) Disconnect oxygen sensor electrical connector
(Fig. 28). (2) Remove sensor using Tool C-4907 (Fig. 29).
Slightly tightening the sensor can ease removal. When the sensor is removed, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E tap.
If using original sensor, coat the threads with Loctite
771-64 anti-seize compound or equivalent. New sen-
sors are packaged with compound on the threads and
do not require additional compound. The sensor must
be tightened to 27 N Im (20 ft. lbs.) torque.
Fig. 27 Oxygen SensorÐ3.3L Engine
Fig. 28 Oxygen Sensor Connector
Fig. 29 Oxygen Sensor Socket
Ä FUEL SYSTEMS 14 - 177

POWER STEERING PUMPÐINITIAL OPERATION
CAUTION: The fluid level should be checked with
engine off to prevent injury from moving compo-
nents. Use only Mopar TPower Steering Fluid. Do
not use automatic transmission fluid. Do not over-
fill.
Wipe filler cap clean, then check the fluid level.
The dipstick should indicate FULL COLDwhen the
fluid is at normal temperature of approximately 21ÉC
to 27ÉC (70ÉF to 80ÉF). (1) Fill power steering pump fluid reservoir to the
proper level. (2) Start the engine and let run for a few seconds.
Then turn the engine off.
(3) Add fluid if necessary. Repeat the above proce-
dure until the fluid level remains constant after run-
ning the engine. (4) Raise front wheels of vehicle off the ground.
(5) Start the engine. Slowly turn the steering
wheel right and left, lightly contacting the wheel
stops. Then turn the engine off. (6) Add power steering fluid if necessary.
(7) Lower the vehicle and turn the steering wheel
slowly from lock to lock. (8) Stop the engine. Check the fluid level and refill
as required. (9) If the fluid is extremely foamy, allow the vehi-
cle to stand a few minutes and repeat the above pro-
cedure.
Fig. 4 Remove Reservoir (Typical)Fig. 5 Flow Control Valve Fitting Removal/Installation
19 - 24 STEERING Ä

(8) Remove the upper to lower steering coupler re-
taining nut and pinch bolt (Fig. 6). Remove the upper
steering coupler from the lower steering coupler shaft.
(9) Place the gear shift lever in either the neutral
or park position. (10) Remove the PRNDL indicator actuation cable
from the steering column actuating arm (Fig. 7).
(11) Release the lock bar on the column insert.
Squeeze the legs of the column insert together and re-
move insert from steering column assembly (Fig. 7).
(12) Secure the insert and actuation cable out of
the way. (13) Remove tilt lever (if equipped) from steering
column.
(14) Remove the upper and lower lock housing
shrouds (Fig. 1) from the steering column assembly. Re-
move the lower fixed shroud from the steering column
assembly. The shroud fasteners are Torx-headscrews.
(15) Remove the wiring harness connector to the
turn signal/multi-function switch using a 7mm
socket as shown in (Fig. 8). (16) Remove the electrical connections from the
Key-in Switch & Halo Light, Main Ignition Switch,
Horn connection or Clock Spring (Speed Control
Equipped) (Fig. 9). (17) Loosen the upper steering column support
bracket nuts (Fig.10) to allow some slack. This will
aid in removal of the upper fixed shroud. (18) Remove the upper fixed shroud (Fig. 1) from
the steering column assembly. Remove the wiring
harness from the steering column assembly by pry-
ing out the plastic retainer buttons (Fig. 8). (19) Remove the lower dash panel and support
bracket standoff fasteners (Fig. 1). (20) Remove the steering column assembly out
through the passenger compartment. Use care to
avoid damaging the paint or interior trim.
Fig. 5 Steering Column Cover Removed
Fig. 6 Steering Column Coupler Remove and Install
Fig. 7 PRNDL Cable Removal
Ä STEERING 19 - 31

(16) Connect the battery ground (negative) cable.
Test the operation of the lights and horns. If applica-
ble, reset the clock and radio.
STEERING COLUMN COMPONENT SERVICE
The Acustar tilt and standard steering columns
(Fig.1) have been designed to be serviced as an as-
sembly; less wiring, switches, shrouds, steering
wheel, etc. Also most steering column components
can be serviced without removing the steering col-
umn from the vehicle. For additional information on
electrical components refer to Group 8H Electrical.
GEAR SHIFT LEVER
The gear shift lever (if equipped) is a serviceable
component of the Acustar steering column assembly.
REMOVE (1) Support the steering column assembly as
shown in (Fig. 1) using a suitable size socket. (2) Using a drift of the appropriate size drive the
roll pin out of the steering column and gear shift le-
ver (Fig. 1). Remove the gear shift lever from the
steering column assembly.
INSTALL (1) Support the steering column assembly as
shown in (Fig. 1) using a suitable size socket. (2) Install the gear shift lever into the steering col-
umn assembly. Align the roll pin holes in the gear
shift lever and the steering column assembly. (3) Carefully Install the roll pin into the steering
column assembly and through the shift lever. If the
roll pin binds check the alignment on the holes. Be
sure roll pin is fully installed into the steering col-
umn assembly.
IGNITION SWITCH SERVICE
TEST AND REPAIR
If the ignition switch effort seems to be excessive
due to binding. Follow the procedure outlined below
to determine the cause.
When service procedures are performed on the
Acustar steering column there are certain areas of the
column that can not be tampered with. If a problem re-
lated to these areas of the steering column are detected.
The entire steering column (less the removable compo-
nents) should be replaced see (Fig. 2 and 3).
(1) Remove ignition switch from steering column.
Refer to Group 8H Electrical.
(2) Using a key cylinder, check the turning effort
of the switch.
² If the ignition switch binds look for the following
conditions.
Fig. 1 Gear Shift Lever Removal
Fig. 2 Steering Column Non-Serviceable Components
19 - 34 STEERING Ä