1999 DODGE RAM Ground location

The PCM contains a self-diagnostic system used for
determining an electronic component failure. The PCM self-diagnostic
system will store a Diagnostic Trouble Code (DTC) in PCM memory if
certain electronic problems are present.
DTCs can be retrieved using appropriate scan tool. See SELF-
DIAGNOSTIC SYSTEM. After repairing an electronic system problem,
stored DTC must be cleared from PCM memory. For PCM location, see PCM
LOCATION table.
AB Body
On firewall, near wiper motor.
AN & DN Bodies
Right front fender, near air cleaner.
BR Body
Right front fender, near firewall.
WJ Body
On firewall, near speed control servo.
GOVERNOR PRESSURE SENSOR
NOTE: Governor pressure sensor may also be referred to as governor
pressure transducer.
Governor pressure sensor delivers an output signal to the PCM
indicating the output pressure of governor pressure solenoid. The PCM
uses this signal to control governor pressure. Governor pressure
solenoid is located on valve body. See Fig. 1.
GOVERNOR PRESSURE SOLENOID
Governor pressure solenoid generates governor pressure
required for transmission upshifts and downshifts. Governor pressure
solenoid is located on valve body. See Fig. 1. Inlet side of governor
pressure solenoid is exposed to normal transmission line pressure and
outlet side provides a passage to governor circuit in the valve body.
Governor pressure solenoid regulates transmission line pressure to the
governor circuit. Electrical supply voltage is supplied to governor
pressure solenoid by PCM. The PCM controls the ground circuit to
governor pressure solenoid to provide solenoid operation.
Fig. 1: Identifying Governor Pressure Solenoid, Governor Pressure
Sensor & Transmission Fluid Temperature Sensor
Courtesy of DaimlerChrysler Corp.
OD (OVERDRIVE) OFF SWITCH

Connect a jumper wire between OPS connector terminals. Start engine
and allow to idle for 20 seconds. Increase engine speed to 1600 RPM.
If chime sounds, system is currently functioning properly. If chime
does not sound, go to next step.
4) Remove instrument cluster. See appropriate INSTRUMENT
PANELS article. Disconnect Instrument cluster 10-pin Gray connector
"B". Connect a jumper wire between ground and Dark Blue/Red wire of
instrument cluster 10-pin Gray connector terminal No. 7. Turn ignition
on. If chime sounds, replace instrument cluster. If chime does not
sound, repair open Dark Blue/Red wire.
CHIME INOPERATIVE - KEY IN IGNITION & LF 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 any module connector.
1) Turn ignition off. Open driver's door. If chime does not
sound, go to next step. If chime sounds, system is currently
functioning correctly.
2) Using scan tool, read driver's door ajar switch status. If
scan tool displays LFDOOR AJAR SWITCH: CLOSED, go to next step. If
scan tool does not display LFDOOR AJAR SWITCH: CLOSED, go to OPEN LEFT
DOOR AJAR CIRCUIT.
3) Using scan tool, read key-in ignition chime state. If scan
tool does not display KEY-IN IGNITION CHIME STATE: ON, go to next
step. If scan tool displays KEY-IN IGNITION CHIME STATE: ON, replace
Central Timer Module (CTM). CTM is located under left side of
instrument panel.
4) Disconnect key-in ignition switch connector. See Fig. 1.
Connect jumper wire between key-in ignition switch connector Light
Blue wire and ground. Using scan tool, read key-in ignition chime
state. If scan tool does not display KEY-IN IGNITION CHIME STATE: ON,
go to next step. If scan tool displays KEY-IN IGNITION CHIME STATE:
ON, replace ignition switch. See appropriate STEERING COLUMN SWITCHES
article.
Fig. 1: Identifying Steering Column Harness Connector Locations
Courtesy of Chrysler Corp.
5) Access CTM 14-pin Green connector C1. Remove connector
cover. Do not disconnect connector. Connect a backprobe jumper wire

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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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

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

No. 1 (Tan/Red wire). If resistance is less than 5 ohms, repair short
to ground. Perform TEST VER-4A under VERIFICATION TESTS. If resistance
is 5 ohms or more, go to next step.
10) Using an ohmmeter, check resistance between ground and
S/C vent solenoid control circuit at S/C servo connector terminal No.
2 (Light Green/Red wire). If resistance is less than 5 ohms, repair
short to ground. Perform TEST VER-4A under VERIFICATION TESTS. If
resistance is 5 ohms or more, go to next step.
11) Using an ohmmeter, measure resistance of S/C vacuum
solenoid control circuit between S/C servo connector terminal No. 1
and PCM connector C3, terminal No. 4 (Tan/Red wire). If resistance is
5 ohms or more, repair open circuit. Perform TEST VER-4A under
VERIFICATION TESTS. If resistance is less than 5 ohms, go to next
step.
12) Using an ohmmeter, check resistance of S/C vent solenoid
control circuit between S/C servo connector terminal No. 2 and PCM
connector C3, terminal No. 5 (Light Green/Red wire). If resistance is
5 ohms or more, repair open circuit. Perform TEST VER-4A under
VERIFICATION TESTS. If resistance is less than 5 ohms, replace S/C
servo. Perform TEST VER-4A under VERIFICATION TESTS.
13) Using an ohmmeter, check resistance between ground and
brake switch output circuit at S/C servo connector terminal No. 3
(Dark Blue/Red wire). If resistance is less than 5 ohms, repair short
to ground. Perform TEST VER-4A under VERIFICATION TESTS. If resistance
is 5 ohms or more, go to next step.
14) Reconnect PCM. Disconnect brake switch connector. Turn
ignition on. Turn S/C on. Using a 12-volt test light, probe S/C power
supply circuit at brake switch connector terminal No. 3 (Yellow/Red
wire). If test light is illuminated and bright, go to next step. If
test light is not illuminated or dim, go to step 17).
15) Turn ignition off. Using an ohmmeter, check resistance of
S/C brake switch output circuit between S/C servo connector terminal
No. 3 and brake switch connector terminal No. 4 (Dark Blue/Red wire).
If resistance is 5 ohms or more, repair open circuit. Perform TEST
VER-4A under VERIFICATION TESTS. If resistance is less than 5 ohms, go
to next step.
16) Check brake switch adjustment. See BRAKE SWITCH under
REMOVAL & INSTALLATION. Adjust as necessary. Perform TEST VER- 4A
under VERIFICATION TESTS. If brake switch adjustment is okay, replace
brake switch. Perform TEST VER-4A under VERIFICATION TESTS.
17) Turn ignition off. Disconnect PCM. Inspect connectors.
Clean or repair as necessary. Using an ohmmeter, measure resistance of
S/C power supply circuit between PCM connector C3, terminal No. 11 and
brake switch connector terminal No. 3 (Yellow/Red wire). If resistance\
is 5 ohms or more, repair open circuit. Perform TEST VER-4A under
VERIFICATION TESTS. If resistance is less than 5 ohms, replace PCM.
Perform TEST VER-4A under VERIFICATION TESTS.
FTC P1596: SPEED CONTROL SWITCH ALWAYS HIGH
FTC P1596 will set if an open circuit is detected in Speed
Control (S/C) switch circuit when ignition is on.
Possible Causes:
* Defective clockspring.
* S/C switch ground circuit open.
* Defective ON/OFF switch.
* Defective PCM.
* S/C switch signal circuit open or shorted to voltage.
NOTE: For component locations, see COMPONENT LOCATIONS. For
connector terminal identification, see CONNECTOR

IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS.
1) Turn ignition on. Using scan tool, read S/C inputs. While
observing display, press S/C ON/OFF switch several times and leave on.
If scan tool displays S/C switch OFF and ON, go to next step. If scan
tool does not display OFF and ON, go to step 3).
2) Using scan tool, measure S/C switch voltage. While
observing display, wiggle wiring between S/C switch and PCM. If
voltage was more than 4.9 volts at any time during wiggling, repair
wiring as necessary. Perform TEST VER-4A under VERIFICATION TESTS. If
voltage was 4.9 volts or less during wiggling, test is complete.
3) Turn ignition off. Disconnect S/C ON/OFF switch. Inspect
connector. Clean or repair as necessary. Using an ohmmeter, measure
resistance of S/C switch ground circuit. 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.
4) Turn ignition on. Using a voltmeter, measure voltage on
S/C switch signal circuit. If voltage is more than 6 volts, repair
short to voltage. Perform TEST VER-4A under VERIFICATION TESTS. If
voltage is 6 volts or less, go to next step.
5) Turn ignition off. Disconnect PCM. Inspect connectors.
Clean or repair as necessary. Using an ohmmeter, measure resistance of
S/C switch signal circuit between ON/OFF switch connector and PCM
connector C3, terminal No. 32 (White/Light Green wire on Ram Van & Ram
Wagon; Red/Light Green wire on all other models). If resistance is
less than 5 ohms, go to next step. If resistance is 5 ohms or more, go
to step 7).
6) Using an ohmmeter, measure resistance across ON/OFF
switch. Resistance should be 20,300-20,700 ohms. If resistance is not
as specified, replace ON/OFF switch. Perform TEST VER-4A under
VERIFICATION TESTS. If resistance is as specified, replace PCM.
Perform TEST VER-4A under VERIFICATION TESTS.
7) Disconnect clockspring 5-pin connector. Clockspring 5-pin
connector is located behind lower steering column shroud. Inspect
connectors. Clean or repair as necessary. Using an ohmmeter, measure
resistance of S/C switch signal circuit between PCM connector C3,
terminal No. 32 and clockspring connector (White/Light Green wire on
Ram Van and Ram Wagon; Red/Light Green wire on all other models). If
resistance is 5 ohms or more, repair open circuit. Perform TEST VER-4A
under VERIFICATION TESTS. If resistance is less than 5 ohms, replace
clockspring. See appropriate AIR BAG RESTRAINT SYSTEMS article.
Perform TEST VER-4A under VERIFICATION TESTS.
FTC P1597: SPEED CONTROL SWITCH ALWAYS LOW
FTC P1597 will set if Speed Control (S/C) switch voltage is
less than 0.39 volts for 2 minutes when ignition is on and battery
voltage is more than 10.4 volts.
Possible Causes:
* S/C ON/OFF switch defective.
* S/C RESUME/ACCEL switch defective.
* S/C switch signal circuit shorted to ground.
* Defective PCM.
* Defective clockspring.
NOTE: For component locations, see COMPONENT LOCATIONS. For
connector terminal identification, see CONNECTOR
IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS.
1) Turn ignition on. Using scan tool, read S/C switch

voltage. If voltage is less than one volt, go to next step. If voltage
is one volt or more, condition to set FTC is not present at this time.
Test is complete.
2) While observing scan tool, disconnect S/C ON/OFF switch.
If S/C switch voltage changes to 5 volts, replace S/C ON/OFF switch.
Perform TEST VER-4A under VERIFICATION TESTS. If voltage does not
change to 5 volts, go to next step.
3) While observing scan tool, disconnect S/C RESUME/ACCEL
switch. If S/C switch voltage changes to 5 volts, replace S/C
RESUME/ACCEL switch. Perform TEST VER-4A under VERIFICATION TESTS. If
voltage does not change to 5 volts, go to next step.
4) Turn ignition off. Ensure both S/C switches are still
disconnected. Using an ohmmeter, check resistance between S/C switch
connector terminals (S/C switch signal circuit and S/C switch ground
circuit). If resistance is less than 5 ohms, repair short circuit.
Perform TEST VER- 4A under VERIFICATION TESTS. If resistance is 5 ohms
or more, go to next step.
5) Disconnect clockspring 4-pin connector. Clockspring 4-pin
connector is located behind steering wheel. Inspect connector. Clean
or repair as necessary. Using an ohmmeter, check resistance between
ground and S/C switch signal circuit at clockspring connector (Dark
Green/Red wire on all models except Ram Van and Ram Wagon; wire color
is not available for Ram Van and Ram Wagon). If resistance is less
than 5 ohms, repair short to ground. Perform TEST VER-4A under
VERIFICATION TESTS. If resistance is 5 ohms or more, go to next step.
6) Disconnect PCM. Inspect connectors. Clean or repair as
necessary. Using an ohmmeter, check resistance between ground and S/C
switch signal circuit at either S/C switch connector (Dark Green/Red
wire on all models except Ram Van and Ram Wagon; wire color is not
available for Ram Van and Ram Wagon). If resistance is less than 5
ohms, repair short to ground. Perform TEST VER-4A under VERIFICATION
TESTS. If resistance is 5 ohms or more, replace PCM. Perform TEST VER-
4A under VERIFICATION TESTS.
FTC P1683: SPEED CONTROL POWER RELAY CIRCUIT
FTC P1683 will set if Speed Control (S/C) power supply
circuit is open or shorted when S/C is turned on.
Possible Causes:
* Brake switch out of adjustment.
* S/C brake switch output circuit open or shorted.
* Defective S/C servo.
* Defective brake switch.
* S/C vacuum or vent solenoid control circuits open or
shorted.
* Defective PCM.
* Ground circuit open.
* S/C power supply circuit open.
NOTE: For component locations, see COMPONENT LOCATIONS. For
connector terminal identification, see CONNECTOR
IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS.
NOTE: Ensure brake pedal is not depressed during the following
steps.
1) Turn ignition off. Disconnect S/C servo connector. Inspect
connector. Clean or repair as necessary. Turn ignition on. Using scan
tool, actuate S/C relay. Using a 12-volt test light, probe S/C 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

* PNP switch defective.
* PNP switch sense circuit open or shorted.
* PNP switch stuck.
* PCM defective.
NOTE: For component locations, see COMPONENT LOCATIONS. For
connector terminal identification, see CONNECTOR
IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS.
1) Turn ignition on. Using scan tool, read PNP switch state.
While observing scan tool, move gear selector between Park and
Reverse. If scan tool displays P/N and D/R, go to next step. If scan
tool does not display P/N and D/R, go to step 3).
2) Turn ignition off. Inspect wiring and connectors related
to PNP switch. Repair as necessary. Perform TEST VER-5A under
VERIFICATION TESTS. If wiring and connectors are okay, condition to
set FTC is not present at this time. Test is complete. Use freeze
frame data to determine conditions when FTC was set.
3) Turn ignition off. Disconnect PCM. Inspect connectors.
Clean or repair as necessary. Using an ohmmeter, check resistance
between ground and PNP switch sense circuit at PCM connector C1,
terminal No. 6 (Black/White wire). While observing ohmmeter, move gear\
selector from Park to Reverse and back to Park. If resistance switched
from less than 10 ohms to more than 10 ohms, replace PCM. Perform TEST
VER-5A under VERIFICATION TESTS. If resistance was less than 10 ohms
at all times, go to next step. If resistance was more than 10 ohms at
all times, go to step 5).
4) Disconnect PNP switch. Inspect connectors. Clean or repair
as necessary. Using an ohmmeter, check resistance between ground and
PNP switch sense circuit. 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, repair or replace stuck PNP switch.
Perform TEST VER-5A under VERIFICATION TESTS.
5) Using an ohmmeter, check resistance of PNP switch circuit
between PNP switch connector and PCM connector C1, terminal No. 6
(Black/White wire). If resistance is 5 ohms or more, repair open
circuit. Perform TEST VER-5A under VERIFICATION TESTS. If resistance
is less than 5 ohms, replace PNP switch. Perform TEST VER-5A under
VERIFICATION TESTS.
SYSTEM TESTS
NOTE: For component locations, See COMPONENT LOCATIONS. For
connector terminal identification, see CONNECTOR
IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS.
CHECKING SPEED CONTROL OPERATION
NOTE: Perform this test only if there are no DTCs.
1) Turn ignition on. Using scan tool, monitor S/C switch
inputs. Press S/C ON/OFF switch several times. If scan tool displays
speed control switch on and off, go to next step. If scan tool does
not display speed control switch on and off, go to NTC-3: SPEED
CONTROL ON/OFF SWITCH.
2) While observing scan tool, press RESUME/ACCEL switch
several times. If scan tool displays RESUME/ACCEL switch PRESSED and
RELEASED, go to next step. If scan tool does not display PRESSED and
RELEASED, go to NTC-4: SPEED CONTROL RESUME/ACCEL SWITCH.
3) While observing scan tool, press brake pedal several
times. If scan tool displays brake pedal PRESSED and RELEASED, go to