ad blue DODGE RAM 1999 Service Owner's Manual

circuit.
ONE GAUGE NOT OPERATING PROPERLY
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting or connecting any module connector.
1) Push and hold RESET button while cycling ignition key; ON-
OFF-ON. Instrument cluster self-test will start. If inoperative gauge
reached proper calibration point, go to next step. If inoperative
gauge did not reach proper calibration point, replace instrument
cluster.
2) Stop instrument cluster self-test. If problem is with
speedometer, go to next step. If problem is with oil pressure gauge,
go to step 5). If problem is with temperature gauge, go to step 14).
If problem is with fuel level gauge, go to appropriate SELF-
DIAGNOSTICS article in ENGINE PERFORMANCE section and review
powertrain symptoms. If problem is with volt gauge, go to step 16). If
problem is with tachometer, go to step 18).
3) Using scan tool, select BODY, SYSTEMS TESTS then PCM
MONITOR. If scan tool displays PCM ACTIVE ON BUS, go to next step. If
scan tool does not display PCM ACTIVE ON BUS, go to appropriate
VEHICLE COMMUNICATIONS article.
4) Raise and support all wheels. Start engine and place gear
selector in drive. Using scan tool, select MIC, MONITORS then CCD BUS
ENGINE INFO. Read VSS. If vehicle speed on scan tool matches
speedometer, see appropriate ANTI-LOCK BRAKE article. If vehicle speed
on scan tool does not match speedometer, replace instrument cluster
circuit board.
5) Turn ignition on. If CHECK GAUGES light illuminated, go to
next step. If CHECK GAUGES light did not illuminate, go to step 11).
6) Turn ignition off. Inspect oil level. If oil level is
within specification, go to next step. If oil level is not within
specification, adjust oil level and retest.
7) Turn ignition on. Disconnect engine Oil Pressure Switch
(OPS) connector. OPS is located near bottom of distributor. If CHECK
GAUGES light went out, go to next step. If CHECK GAUGES light did not
go out, go to step 10).
8) Remove OPS. Connect mechanical oil pressure gauge to OPS
port. Start engine. If engine oil pressure at idle is 4 psi or more,
go to next step. If engine oil pressure at idle is less than 4 psi,
repair mechanical engine problem.
9) Run engine to reach normal operating temperature. If
engine oil pressure at idle is 4 psi or more, replace OPS. If engine
oil pressure at idle is less than 4 psi, repair mechanical engine
problem.
10) Turn ignition off. Disconnect PCM White connector C2. PCM
is located in engine compartment on right inner fender. Using an
external ohmmeter, measure resistance between ground and PCM Black
connector terminal No. 23 (Gray/Orange wire). If resistance is less
than 5 ohms, repair short to ground in Gray/Orange wire. If resistance
is 5 ohms or more, replace PCM.
11) Disconnect engine Oil Pressure Switch (OPS) connector.
OPS is located near bottom of distributor. Using an external ohmmeter,
measure resistance between ground and OPS connector Black/Light Blue
wire. If resistance is less than 5 ohms, go to next step. If
resistance is 5 ohms or more, repair open Black/Light Blue wire.
Black/Light Blue wire is a common sensor ground. If no other engine
sensors are failed, repair ground between sensor and splice. If

NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
If temperature reading is off by more than 5
F, ambient
temperature sensor is defective. Replace ambient temperature sensor.
Ambient temperature sensor is located on left radiator saddle.
REPAIRING "OC" IN CMTC DISPLAY
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Drive
vehicle at least 3 miles (greater than 25 MPH) to update CMTC\
and perform VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting any module connector.
1) Disconnect ambient temperature sensor connector. Sensor is
located on left radiator saddle. Connect jumper wire between sensor
connector terminals. Turn ignition on. Observe CMTC display. If CMTC
displays SC, replace ambient temperature sensor. If CMTC does not
display SC, go to next step.
2) Turn ignition off. Disconnect jumper wire. Disconnect CMTC
module connector. Connect a jumper wire between ground and ambient
temperature sensor harness connector Violet/Light Green wire. If CMTC
displays SC, repair open Black/Violet wire between ambient temperature
sensor harness connector and ground. If CMTC does not display SC, go
to next step.
3) Connect a backprobe jumper wire between ground and CMTC
harness connector terminal No. 3 (Violet/Light Green wire). If CMTC
displays SC, repair open Violet/Light Green wire between ambient
temperature sensor harness connector and CMTC connector. If CMTC does
not display SC, replace CMTC module.
REPAIRING "SC" IN CMTC DISPLAY
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting any module connector.
1) Turn ignition off. Disconnect CMTC connector. Using an
external ohmmeter, measure resistance between CMTC harness connector
terminal No. 3 (Violet/Light Green wire) and terminal No. 7
(Black/Light Green wire). If resistance is less than 5 ohms, repair
Violet/Light Green wire between CMTC module and ambient temperature
sensor for short to ground. If resistance is 5 ohms or more, go to
next step.
2) Measure resistance between CMTC harness connector terminal
No. 9 (Black/Light Blue wire) and terminal No. 3 (Violet/Light Green
wire). If resistance is less than 1000 ohms, repair Violet/Light Green
wire for short to Black/Light Blue wire. If resistance is 1000 ohms or
more, go to next step.
3) Disconnect ambient temperature sensor connector. Sensor is
located on left radiator saddle. Observe CMTC display. If CMTC
displays OC, replace ambient temperature sensor. If CMTC does not
display OC, replace CMTC module.

does not display BUS OPERATIONAL, go to appropriate VEHICLE
COMMUNICATIONS article.
2) Using scan tool select BODY COMPUTER. If scan tool
displays NO RESPONSE, go to appropriate VEHICLE COMMUNICATIONS
article. If scan tool does not displays NO RESPONSE, go to next step.
3) This test is only for vehicles equipped with speed
sensitive door locks. With doors closed and unlocked drive vehicle
faster than 15 MPH. If doors lock, system is currently functioning
properly. If doors do not lock, using scan tool select ROLLING LOCKS.
Retest system.
DOORS LOCK WITH KEY IN IGNITION & LEFT DOOR OPEN
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting or connecting any module connector.
1) Using scan tool select SYSTEM MONITORS, then CCD BUS TEST.
If scan tool displays BUS OPERATIONAL, go to next step. If scan tool
does not display BUS OPERATIONAL, go to appropriate VEHICLE
COMMUNICATIONS article.
2) Using scan tool select BODY COMPUTER. If scan tool
displays NO RESPONSE, go to appropriate VEHICLE COMMUNICATIONS
article. If scan tool does not display NO RESPONSE, go to next step.
3) Place key in ignition. Open driver's door. Lock doors from
interior lock switch. If doors locked, go to next step. If doors did
not lock, system is currently functioning correctly.
4) Using scan tool, read left door ajar status. Open and
close left door. If door ajar state changed from OPEN to CLOSED, go to
next step. If door ajar state did not change from OPEN to CLOSED, go
to OPEN LEFT DOOR AJAR CIRCUIT under DOOR AJAR SYSTEM.
5) Ensure driver's door is open. Read key-in ignition status.
If scan tool shows KEY-IN, replace Central Timer Module (CTM). CTM is
located behind right kick panel. If scan tool does not show KEY-IN, go
to next step.
6) Gain access to CTM connector C1. Do not disconnect
connector. Using an external voltmeter, measure voltage between ground
and CTM 14-pin connector C1 terminal No. 9 (Light Blue wire). If
voltage is more than 1.5 volts, repair open Light Blue wire. If
voltage is 1.5 volts or less, go to next step.
7) Turn ignition off and remove key. Measure voltage between
ground and CTM 14-pin connector C1 terminal No. 9 (Light Blue wire).
If voltage is less than 1.5 volts, replace CTM. If voltage is 1.5
volts or more, replace ignition switch.
ONE OR ALL DOORS FAILING TO LOCK FROM ONE SWITCH (ONE OR ALL
DOORS FAILING TO UNLOCK FROM ONE SWITCH)
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting or connecting any module connector.
1) Using scan tool select SYSTEM MONITORS, then CCD BUS TEST.
If scan tool displays BUS OPERATIONAL, go to next step. If scan tool
does not display BUS OPERATIONAL, go to appropriate VEHICLE
COMMUNICATIONS article.
2) Using scan tool select BODY COMPUTER. If scan tool

right kick panel. Disconnect CTM 18-pin connector C2. Turn ignition
on. Using an external voltmeter, measure voltage between ground and
CTM 18-pin connector C2 terminal No. 18 (Black/Red wire). If voltage
is more than 9.5 volts, replace CTM. If voltage is 9.5 volts or less,
repair open in Black/Red wire between CTM and horn relay.
6) Remove security relay from Power Distribution Center
(PDC). Turn ignition on. Connect a test light between battery source
and headlight relay connector terminal No. 85 (Red/Dark Blue wire).
Using scan tool, actuate relay. If test light illuminates, replace
security relay. If test light does not illuminate, go to next step.
7) Using an external voltmeter, measure voltage between
battery voltage and security relay connector terminal No. 86
(Red/Orange wire). If voltage is more than 9.5 volts, go to next step.\
If voltage is 9.5 volts or less, repair open in Red/Orange wire
between battery source and security relay.
8) Reinstall security relay. Locate Central Timer Module
(CTM). CTM is located behind right kick panel. Disconnect CTM 18-pin
connector C2. Using an external voltmeter, measure voltage between
ground and CTM 18-pin connector C2 terminal No. 6 (Red/Dark Blue
wire). If voltage is more than 9.5 volts, replace CTM. If voltage is
9.5 volts or less, repair open in Red/Dark Blue wire between CTM and
security relay.
9) Disconnect overhead console 12-pin connector. Using an
external voltmeter, measure voltage between battery and overhead
console 12-pin connector terminal No. 11 (Black wire). Using scan
tool, actuate VTSS indicator light. If voltage is about 10 volts,
replace overhead console. If voltage is not about 10 volts, go to next
step.
10) Measure voltage between ground and overhead console 12-
pin connector terminal No. 5 (Pink wire). Turn ignition on. If voltage\
is more than 10 volts, go to next step. If voltage is 10 volts or
less, repair open Pink wire.
11) Locate Central Timer Module (CTM). CTM is located behind\
right kick panel. Disconnect CTM 18-pin connector C2. Turn ignition
on. Using an external ohmmeter, measure resistance between ground and
CTM 18-pin connector C2 terminal No. 8 (Black wire). If resistance is
5 ohms or more, replace CTM. If resistance is less than 5 ohms, repair
open Black wire between CTM and VTSS indicator light.
12) Using scan tool, place VTSS in diagnostic mode and follow
directions on screen. If TURN KEY TO ACC POSITION is not displayed, go
to step 24). If NO RESPONSE after turning key to accessory position or
TURN KEY TO ACC POSITION is displayed longer than 15 seconds, go to
next step. If neither response is received, go to step 14).
13) Locate Central Timer Module (CTM). CTM is located behind\
right kick panel. Gain access to CTM 18-pin connector C2. Ensure key
is in accessory position. Using an external voltmeter, measure voltage
between ground and backprobe of CTM 18-pin connector C2 terminal No. 5
(Dark Blue/White wire). If voltage is more than 10 volts, replace CTM.\
If voltage is 10 volts or less, repair open Dark Blue/White wire
between CTM and junction block.
14) Remove key from ignition. Wait 2 seconds after performing
each of the following actions. Open, then close both door. Operate
power door lock switch to lock, then unlock position. Rotate key both
directions in both doors. Ensure each operation is successful. If any
operation is unsuccessful, see VTSS SYMPTOM DIRECTORY table for repair
of failed operation. If all operations are successful, go to step 22).
VTSS SYMPTOM DIRECTORY









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Problem Circuit Go To
Driver's Door Open Or Close ............................... Step 15)

disarm switch state CLOSED, replace CTM.
23) Turn ignition switch to START position. If horn does not
sound, go to next step. If horn sounds, go to step 24).
24) Locate Central Timer Module (CTM). CTM is located behind\
right kick panel. Disconnect CTM 14-pin connector C1. Using an
external voltmeter, measure voltage between ground and CTM 14-pin
connector C1 terminal No. 8 (Dark Blue/White wire). If voltage is more\
than 10 volts, replace CTM. If voltage is 10 volts or less, repair
open Dark Blue/White wire between CTM and RUN-ACC fuse in junction
block.
WINDSHIELD WIPER SYSTEM
WIPER PARK SWITCH FAILURE
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting or connecting any module connector.
NOTE: It takes 8 seconds for wiper park switch failure DTC to set.
1) Using scan tool, clear DTCs. See appropriate SELF-
DIAGNOSTICS article. Operate wipers in low speed, then intermittent
mode. Reread DTCs. If WIPER PARK SWITCH FAILURE is displayed, go to
next step. If WIPER PARK SWITCH FAILURE is not displayed, system is
currently functioning properly.
2) Gain access to wiper motor connector. Using an external
voltmeter, measure voltage between ground and wiper motor terminal No.
2 (Dark Green wire). If voltage is more than 9 volts, go to next step.\
If voltage is 9 volts or less, replace wiper motor.
3) Locate Central Timer Module (CTM). CTM is located under
left side of instrument panel. Using an external voltmeter, measure
voltage between ground and backprobe of CTM 14-pin Green connector C1
terminal No. 11 (Dark Green wire). If voltage is 9 volts or less,
replace CTM. If voltage is more than 9 volts, repair short to voltage
in Dark Green wire between CTM and wiper relay or wiper motor.
INTERMITTENT WIPERS INOPERATIVE
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting or connecting any module connector.
1) Using scan tool select CENTRAL TIMER MODULE. If scan tool
displays NO RESPONSE, go to appropriate VEHICLE COMMUNICATIONS
article. If scan tool displays any CCD bus failure message, go to
SYMPTOM IDENTIFICATION. If scan tool does not display NO RESPONSE or
any CCD bus failure message, go to next step.
2) If problem is wipers parking in wrong position, go to next
step. If problem is not wipers parking in wrong position, go to step
5).
3) Gain access to wiper motor connector. Turn wipers on to
low speed. Using an external voltmeter, measure voltage between ground
and wiper motor switch terminal No. 2 (Dark Green wire). If voltage
does not cycle between zero and 12 volts, replace wiper motor. If
voltage cycles between zero and 12 volts, go to next step.

4) Locate Central Timer Module (CTM). CTM is located under
left side of instrument panel. Using an external voltmeter, measure
voltage between ground and backprobe of CTM 14-pin Green connector C1
terminal No. 11 (Dark Green wire). Wipers should be operating at low
speed. If voltage does not cycle between zero and 12 volts, repair
open Dark Green wire between CTM and wiper relay or wiper motor. If
voltage cycles between zero and 10 volts, replace CTM.
5) Using scan tool, monitor intermittent wiper voltage level.
Rotate wiper switch from low intermittent to high intermittent level.
If voltage changes from approximately 2.5 to 12 volts, replace CTM. If
voltage does not change from approximately 2.5 to 12 volts, go to next
step.
6) Disconnect 24-pin multifunction switch connector. Using an
external ohmmeter, measure resistance of White/Dark Blue wire between
multifunction switch connector terminal No. 1 and CTM 14-pin Green
connector C1 terminal No. 12. if resistance is less than 5 ohms,
replace multifunction switch. If resistance is 5 ohms or more, repair
open White/Dark Blue wire between multifunction switch and CTM.
NO WIPER ACTUATION AFTER WASH BUTTON PUSHED
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting or connecting any module connector.
1) Using scan tool select Central Timer Module (CTM). If sca\
n
tool displays NO RESPONSE, go to appropriate VEHICLE COMMUNICATIONS
article. If scan tool displays any CCD bus failure message, go to
SYMPTOM IDENTIFICATION. If scan tool does not display NO RESPONSE or
any CCD bus failure message, go to next step.
2) Turn ignition on. If washer system works, go to next step.
If washer system does not work, see appropriate WIPER/WASHER SYSTEMS
article.
3) Using scan tool, actuate washer. If washer pump sense
displays ON, replace CTM. If washer pump sense does not display ON,
repair open Brown wire between CTM 14-pin connector C1 terminal No. 10
and multifunction switch.
WIPER SPEED SENSITIVE FEATURE INOPERATIVE
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1A after each repair.
CAUTION: Always turn ignition switch to OFF position prior to
disconnecting or connecting any module connector.
1) Using scan tool select Central timer module (CTM). If sca\
n
tool display is not blank or have a CCD bus failure message, go to
next step. If scan tool display is blank or has a CCD bus failure
message, see appropriate VEHICLE COMMUNICATIONS article.
2) Using scan tool, select Powertrain Control Module (PCM).
If scan tool display is not blank or have a CCD bus failure message,
go to next step. If scan tool display is blank or has a CCD bus
failure message, see appropriate VEHICLE COMMUNICATIONS article.
3) Raise and support vehicle. Turn wipers on to lowest
intermittent position. Time interval between wipes. Spin rear wheels
to more than 15 MPH. If interval between wipes decreased to
approximately 18 seconds, system is currently functioning properly. If
interval between wipes did not decrease to approximately 18 seconds,

Fig. 2: Adjusting Transfer Case Shift Linkage (Ram Pickup)
Courtesy of Chrysler Corp.
TROUBLE SHOOTING
NOTE: For trouble shooting not covered in this article, see
appropriate table in TROUBLE SHOOTING article in GENERAL
INFORMATION.
Hydraulic system should not require addition of fluid under
normal circumstances. Reservoir fluid level will increase as normal
clutch wear occurs. Avoid overfilling or removing fluid from
reservoir. This will cause clutch release problems.
TESTING
CLUTCH PEDAL POSITION SWITCH
NOTE: The position switch is an integral part of clutch master
cylinder push rod and cannot be serviced separately.
Disconnect clutch pedal position switch electrical connector.
Depress switch. Using a DVOM, measure continuity between clutch pedal
position switch terminals No. 1 (Yellow/Red wire) and No. 2 (Dark
Blue/Yellow wire). If continuity exists, switch is okay. If continuity
does not exist, replace clutch master cylinder. See CLUTCH MASTER
CYLINDER under REMOVAL & INSTALLATION.

operator's foot off accelerator pedal, S/C compensates for excessive
S/C cable slack. If lift foot sets are continually used, speed control
overshoot/undershoot condition will develop.
To "unlearn" overshoot/undershoot condition, operator must
press and release set button while maintaining desired speed with
accelerator pedal, then turn S/C switch to OFF position after waiting
10 seconds. This procedure must be repeated 10-15 times to completely
unlearn overshoot/undershoot condition.
COMPONENT TESTS
WARNING: Vehicle is equipped with an air bag. Air bag must be
deactivated before servicing speed control components on or
around steering column. See appropriate AIR BAG RESTRAINT
SYSTEMS article.
NOTE: For component locations, See COMPONENT LOCATIONS. For
connector terminal identification, see CONNECTOR
IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS.
BRAKE SWITCH
Disconnect brake switch 6-pin connector. Using an ohmmeter,
check for continuity at brake switch. See Fig. 1. If continuity is not
as specified in BRAKE SWITCH CONTINUITY table, check brake switch
adjustment. See BRAKE SWITCH under REMOVAL & INSTALLATION. If brake
switch adjustment is okay, replace defective brake switch.
BRAKE SWITCH CONTINUITY








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Switch Plunger  Check Between  Continuity 


Position  Terminals  










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Released  5 & 6  Yes 










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Depressed  1 & 2  Yes 











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SPEED CONTROL SERVO
1) Start engine. Disconnect Speed Control (S/C) servo 4-pin
connector. Turn S/C on. Using a voltmeter, check voltage at S/C servo
connector terminal No. 3 (Dark Blue/Red wire). Battery voltage should
exist when brake pedal is not depressed. If battery voltage exists, go
to next step. If battery voltage does not exist, check circuit between
brake switch and S/C servo. See WIRING DIAGRAMS.
2) Connect a jumper wire between S/C servo pin No. 3 and S/C
servo connector terminal No. 3. Check voltage at S/C servo pins No. 1,
2 and 4. If battery voltage does not exist, replace S/C servo. If
battery voltage exists, go to next step.
3) Turn ignition off. Check for continuity between S/C servo
connector terminal No. 4 and ground. If continuity exists, test is
complete. If continuity does not exist, repair open ground circuit as
necessary.
VACUUM SUPPLY
Gasoline Engines
1) Disconnect vacuum hose at speed control servo. Install
vacuum gauge to disconnected vacuum hose. Start engine and observe

scan tool displayed P/N and D/R in correct positions, go to next step.
4) Raise drive wheels and support vehicle, allowing wheels to
spin. Using scan tool, erase DTCs. Start engine. Using scan tool, read
Output Speed Sensor (OSS). Shift transmission into first gear. While
observing scan tool, allow wheels to spin at a speed less than 15 MPH.
If scan tool displays OSS more than 60 RPM, go to next step. If scan
tool displays OSS 60 RPM or less, go to step 7).
5) While wheels are spinning, wiggle wiring between OSS and
PCM. If OSS reading dropped while wiggling, repair intermittent short
or open circuit. Perform TEST VER-5A under VERIFICATION TESTS. If OSS
reading did not drop, go to next step.
6) Using scan tool, erase DTCs. Road test vehicle. Read DTCs.
If FTC P0720 returns, replace PCM. Perform TEST VER-5A under
VERIFICATION TESTS. If FTC P0720 did not return, go to step 13).
7) Turn ignition off. Disconnect PCM. Inspect connectors.
Clean or repair as necessary. Using an ohmmeter, measure resistance
between ground and OSS signal circuit at PCM connector C2, terminal
No. 28 (Light Green/Black wire on Ram Pickup; Light Green/White wire
on all other models). If resistance is less than 5 ohms, repair short
to ground. Perform TEST VER-5A under VERIFICATION TESTS.
8) Using an ohmmeter, measure resistance between ground and
OSS ground circuit at PCM connector C2, terminal No. 25 (Dark
Blue/Black wire). If resistance is less than 5 ohms, repair short to
ground. Perform TEST VER-5A under VERIFICATION TESTS. If resistance is
5 ohms or more, go to next step.
9) Disconnect OSS. Using an ohmmeter, measure resistance
across OSS terminals. If resistance is not 300-1200 ohms, replace OSS.
Perform TEST VER-5A under VERIFICATION TESTS. If resistance is 300-
1200 ohms, go to next step.
10) Using an ohmmeter, measure resistance of OSS signal
circuit between PCM connector C2, terminal No. 28 and OSS connector
(Light Green/Black wire on Ram Pickup; Light Green/White wire on all
other models). If resistance is more than 5 ohms, repair open circuit.
Perform TEST VER-5A under VERIFICATION TESTS. If resistance is 5 ohms
or less, go to next step.
11) Using an ohmmeter, measure resistance of OSS ground
circuit between PCM connector C2, terminal No. 25 and OSS connector
(Dark Blue/Black wire). If resistance is more than 5 ohms, repair open\
circuit. Perform TEST VER-5A under VERIFICATION TESTS. If resistance
is 5 ohms or less, go to next step.
12) Reconnect OSS. Using an ohmmeter, measure resistance
between PCM connector C2, terminals No. 25 (Dark Blue/Black wire) and
No. 28 (Light Green/Black wire on Ram Pickup; Light Green/White wire
on all other models). If resistance is 300-1200 ohms, replace PCM.
Perform TEST VER-5A under VERIFICATION TESTS. If resistance is not
300-1200 ohms, go to next step.
13) Inspect wiring and connectors. repair as necessary.
Perform TEST VER-5A under VERIFICATION TESTS. If wiring and connectors
are okay, go to next step.
14) Conditions required to set FTC are not present at this
time. Check freeze frame data to determine conditions when FTC was
set. Raise drive wheels and support vehicle, allowing wheels to spin.
Using scan tool, read OSS. Shift transmission into first gear. While
observing scan tool, allow wheels to spin at a speed less than 15 MPH.
Wiggle wiring between OSS and PCM. If OSS reading dropped while
wiggling, repair intermittent short or open circuit. Perform TEST VER-
5A under VERIFICATION TESTS. If OSS reading did not drop, no problem
is indicated at this time.
FTC P1595: SPEED CONTROL SOLENOID CIRCUITS
Speed Control (S/C) solenoid circuits are monitored when
engine is running, S/C switch is on and battery voltage is more than

10.4 volts. FTC P1595 will set if vacuum and vent solenoids do not
respond when actuated by PCM.
Possible Causes:
* Ground circuit open.
* S/C brake switch output circuit open.
* S/C power supply circuit open or shorted.
* S/C servo defective.
* S/C vacuum solenoid control circuit open or shorted.
* S/C vent solenoid control circuit open or shorted.
* Brake switch defective or out of adjustment.
* Defective PCM.
NOTE: For component locations, see COMPONENT LOCATIONS. For
connector terminal identification, see CONNECTOR
IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS.
1) Turn ignition on. Turn Speed Control (S/C) on. Using scan\
tool, actuate S/C vent solenoid. If speed control servo clicks, go to
next step. If S/C servo does not click, go to step 7).
2) Using scan tool, actuate S/C vacuum solenoid. If S/C servo
clicks, go to next step. If S/C servo does not click, go to step 6).
3) Turn ignition on. Using scan tool, actuate S/C vacuum
solenoid. Wiggle wiring harness between S/C servo and brake switch to
PCM while scan tool is still actuating speed control vacuum solenoid.
If wiggling did not cause an interruption of S/C servo actuation, go
to next step. If wiggling caused an interruption of S/C servo
actuation, repair wiring harness as necessary. Perform TEST VER-4A
under VERIFICATION TESTS.
4) Turn ignition off. Inspect S/C wiring and connectors.
Clean or repair as necessary. Perform TEST VER-4A under VERIFICATION
TESTS. If wiring and connectors are okay, go to next step.
5) Using scan tool, actuate S/C vent solenoid. Wiggle wiring
harness between S/C servo and brake switch to PCM while scan tool is
still actuating speed control vacuum solenoid. If wiggling did not
cause interruption of S/C servo actuation, test is complete. If
wiggling caused interruption of S/C servo actuation, repair wiring
harness as necessary. Perform TEST VER-4A under VERIFICATION TESTS.
6) Using scan tool, actuate S/C vent solenoid. Wiggle wiring
harness between S/C servo and brake switch to PCM while scan tool is
still actuating speed control vacuum solenoid. If wiggling did not
cause interruption of S/C servo actuation, go to next step. If
wiggling caused interruption of S/C servo actuation, repair wiring
harness as necessary. Perform TEST VER-4A under VERIFICATION TESTS.
NOTE: Ensure brake pedal is not depressed during the following
steps.
7) Turn ignition off. Disconnect S/C servo 4-pin connector.
Inspect all related wiring and connectors and repair as necessary.
Turn ignition on. Turn S/C switch on. Using a 12-volt test light,
probe brake switch output circuit at S/C servo connector terminal No.
3 (Dark Blue/Red wire). If test light is illuminated and bright, go to\
next step. If test light is dim or not illuminated, go to step 13).
8) Turn ignition off. Using an ohmmeter, check resistance of
ground circuit at S/C servo connector terminal No. 4 (Black wire). If
resistance is 5 ohms or more, repair open ground circuit. Perform TEST
VER-4A under VERIFICATION TESTS. If resistance is less than 5 ohms, go
to next step.
9) Disconnect PCM. Inspect connectors. Clean or repair as
necessary. Using an ohmmeter, measure resistance between ground and
S/C vacuum solenoid control circuit at S/C servo connector terminal