1999 DODGE RAM can bus

CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Remove and inspect fuse No. 11 from junction block.
Junction block is on left side of instrument panel. If fuse is open,
go to next step. If fuse is okay, go to step 3).
2) Using external ohmmeter, measure resistance between ground
and fused ignition switch output run/start terminal (Dark Blue/White
wire) on fuse No. 11 socket. If resistance is less than 5 ohms, repair
short to ground in Dark Blue/White wire. Replace fuse No. 11. If
resistance is 5 ohms or more, replace fuse No. 11.
3) Install fuse No. 11. Remove and inspect fuse No. 6 from
junction block. If fuse is open, next step. If fuse is okay, go to
step 5).
4) Using external ohmmeter, measure resistance between ground
and fused ignition switch output run/accy terminal (Dark Blue wire) on\
fuse No. 6 socket. If resistance is less than 5 ohms, repair short to
ground in Dark Blue wire. Replace fuse No. 6. If resistance is 5 ohms
or more, replace fuse No. 6.
5) Install fuse No. 6. Disconnect Central Timer Module (CTM)\
.
CTM is located under left side of instrument panel. Using external
ohmmeter, measure resistance between ground and CTM 18-pin connector
terminal No. 3 (Black/Orange wire). If resistance is more than 5 ohms,\
repair open Black/Orange wire. If resistance is 5 ohms or less, go to
next step.
6) Measure resistance between ground and CTM 14-pin connector
terminal No. 6 (Black/Light Green wire). If resistance is more than 5
ohms, repair open Black/Light Green wire. If resistance is 5 ohms or
less, go to next step.
7) Turn ignition on. Using scan tool, perform CCD Bus test.
Connect jumper wire between ground and CTM 18-pin connector terminal
No. 16 (Violet/Brown wire). If scan tool does not display BUS SHORT TO\
GROUND, repair open Violet/Brown wire. If scan tool displays BUS SHORT
TO GROUND, go to next step.
8) Disconnect jumper wire. Connect jumper wire between ground
and CTM 18-pin connector terminal No. 17 (White/Black wire). If scan
tool does not display BUS SHORT TO GROUND, repair open White/Black
wire. If scan tool displays BUS SHORT TO GROUND, replace CTM.
NO RESPONSE INSTRUMENT CLUSTER
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 off prior to disconnecting any module
connector.
1) Turn ignition on. Using scan tool, select BODY CONTROL
MODULE. If scan tool displays NO RESPONSE, go to NO RESPONSE CENTRAL
TIMER MODULE. If scan tool does not display NO RESPONSE, go to next
step.
2) Using scan tool, select SYSTEM TEST. If scan tool displays
PCM ACTIVE ON THE BUS, go to next step. If scan tool does not display
PCM ACTIVE ON THE BUS, go to NO RESPONSE POWERTRAIN CONTROL MODULE.
3) Turn ignition off. Remove instrument cluster. Turn
ignition on. Using scan tool, turn on CCD bus bias under SYSTEM
MONITORS, then CCD BUS VOLTAGE. Connect jumper wire between ground and
instrument cluster connector C1 terminal No. 10 (Violet/Brown wire).
If scan tool voltage did not drop to about zero volts, repair open
Violet/Brown wire. If scan tool voltage dropped to about zero volts,
go to next step.

4) Move jumper to instrument cluster connector C1 terminal
No. 9 (White/Black wire). Monitor CCD BUS VOLTAGE. If scan tool
voltage did not drop to about zero volts, repair open White/Black
wire. If scan tool voltage did not drop to about zero volts, replace
instrument cluster.
NO RESPONSE POWERTRAIN CONTROL MODULE
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) If engine does not run, see appropriate BASIC DIAGNOSTIC
PROCEDURES article in ENGINE PERFORMANCE section. If engine runs, go
to next step.
2) Turn ignition off. Disconnect Powertrain Control Module
(PCM). PCM is mounted in right side of firewall. Turn ignition on.
Connect jumper wire between ground and PCM connector C3 terminal. No.
30 (Violet/Brown wire). Using scan tool, perform CCD BUS test. If scan\
tool does not display SHORT TO GROUND, repair open Violet/Brown wire.
If scan tool displays SHORT TO GROUND, go to next step.
3) Move jumper wire to PCM connector C3 terminal No. 28
(White/Black wire). Perform CCD BUS test. If scan tool does not
display SHORT TO GROUND, repair open White/Black wire. If scan tool
displays SHORT TO GROUND, replace PCM.
NO RESPONSE COMPASS/MINI-TRIP SYSTEM
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Remove and inspect fuse No. 11 from junction block.
Junction block is on left side of instrument panel. If fuse is open,
go to next step. If fuse is okay, go to step 3).
2) Using external ohmmeter, measure resistance between ground
and fused ignition switch output run/start terminal (Dark Blue/White
wire) on fuse No. 11 socket. If resistance is less than 5 ohms, repair
Dark Blue/White wire for short to ground. Replace fuse No. 11. If
resistance is 5 ohms or more, replace fuse No. 11.
3) Reinstall fuse. Disconnect CMTC 12-pin connector. Turn
ignition on. Using external voltmeter, measure voltage between ground
and CMTC connector terminal No. 1 (Dark Blue/White wire). If voltage
is less than 9.5 volts, repair open Dark Blue/White wire. If voltage
is 9.5 volts or more, go to next step.
4) Using external voltmeter, measure voltage between ground
and CMTC connector terminal No. 5 (Pink wire). If voltage is less than\
9.5 volts, repair open Pink wire. If voltage is 9.5 volts or more, go
to next step.
5) Turn ignition off. Using external ohmmeter, measure
resistance between ground and CMTC connector terminal No. 7
(Black/Light Green wire). If resistance is 5 ohms or less, go to next
step. If resistance is more than 5 ohms, repair open Black/Light Green
wire.
6) Using scan tool, perform CCD bus test. Connect jumper wire
between ground and CMTC connector terminal No. 2 (Violet/Brown wire).
If scan tool displays BUS (+) SHORTED TO GROUND, go to next step. If

scan tool does not display BUS (+) SHORTED TO GROUND, repair open
Violet/Brown wire.
7) Move jumper wire to CMTC connector terminal No. 8
(White/Black wire). If scan tool displays BUS (+) SHORTED TO GROUND,\
replace CMTC. If scan tool does not display BUS (+) SHORTED TO GROUND,\
repair open White/Black wire.
NO RESPONSE RADIO
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 off prior to disconnecting any module
connector.
1) If radio screen is not blank, go to step 7). If radio
screen is blank, go to next step.
2) Remove and inspect junction block fuse No. 8 (radio). If
fuse is blown, go to next step. If fuse is okay, go to step 4).
3) Turn ignition off. Disconnect radio Gray connector. Using
external ohmmeter, measure resistance between ground and radio Gray
connector terminal No. 6 (Red/White wire). If resistance is less than
5 ohms, repair Red/White wire for short to ground. Replace junction
block fuse No. 8. If resistance is 5 ohms or more, replace radio.
Replace junction block fuse No. 8.
4) Turn ignition on. Measure voltage between ground and
terminal No. 7 (Pink wire). If voltage is 10 volts or less, repair
open Pink wire. If voltage is more than 10 volts, go to next step.
5) Install fuse. Disconnect radio Gray connector. Using
external voltmeter, measure voltage between ground and radio Gray
terminal No. 6 (Red/White wire). If voltage is 10 volts or less,
repair open Red/White wire. If voltage is more than 10 volts, go to
next step.
6) Inspect ground strap and antenna for correct installation.
Repair as needed. If ground strap and antenna are okay, replace radio.
7) Disconnect 2-pin CCD BUS connector on back of radio.
Connect jumper wire between terminal No. 2 (White/Black wire) and
ground. Using scan tool, select BODY, BODY COMPUTER, then SYSTEM TEST.
Perform CCD BUS test. If scan tool does not display BUS SHORT TO
GROUND, repair open White/Black wire. If scan tool displays BUS SHORT
TO GROUND, go to next step.
8) Move jumper wire to terminal No. 1 (Violet/Brown wire).
Perform CCD BUS test. If scan tool does not display BUS SHORT TO
GROUND, repair open Violet/Brown wire. If scan tool displays BUS SHORT
TO GROUND, replace radio.
NO TERMINATION
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Disconnect Powertrain Control Module (PCM) connectors. PC\
M
is mounted in right side of firewall. Connect jumper wire between
ground and PCM connector C3 terminal No. 30 (Violet/Brown wire). Using\
scan tool, select SYSTEM MONITORS. Perform CCD BUS test. If scan tool
does not display BUS SHORT TO GROUND, repair open Violet/Brown wire.
If scan tool displays BUS SHORT TO GROUND, go to next step.
2) Move jumper wire to PCM connector C3 terminal No. 28

(White/Black wire). Perform CCD BUS test. If scan tool does not
display BUS SHORT TO GROUND, repair open White/Black wire. If scan
tool displays BUS SHORT TO GROUND, replace PCM.
NOT RECEIVING BUS MESSAGES CORRECTLY
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Disconnect anti-lock brake controller module. Controller
module is mounted to top of ABS hydraulic unit. Turn ignition on. If
scan tool displays BUS OPERATIONAL, replace anti-lock brake controller
module. If scan tool does not display BUS OPERATIONAL, go to next
step.
2) Turn ignition off and wait 2 minutes. Disconnect Air Bag
Control Module (ACM). ACM is located under center of instrument panel.\
Turn ignition on. If scan tool displays BUS OPERATIONAL, replace ACM.
If scan tool does not display BUS OPERATIONAL, go to next step.
3) Disconnect Central Timer Module (CTM). CTM is located
under left side of instrument panel. Turn ignition on. If scan tool
displays BUS OPERATIONAL, replace CTM. If scan tool does not display
BUS OPERATIONAL, replace scan tool cable or scan tool.
BUS SHORT TO 5 VOLTS
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Turn ignition off. Disconnect Powertrain Control Module
(PCM). PCM is mounted in right side of firewall. Turn ignition on. If
scan tool does not display BUS SHORT TO 5 VOLTS, go to step 10). If
scan tool displays BUS SHORT TO 5 VOLTS, go to next step.
2) Turn ignition off. Disconnect anti-lock brake controller
module. Controller module is mounted to top of ABS hydraulic unit.
Turn ignition on. If scan tool does not display BUS SHORT TO 5 VOLTS,
replace anti-lock brake controller module. If scan tool displays BUS
SHORT TO 5 VOLTS, go to next step.
3) Turn ignition off. Disconnect instrument cluster. Turn
ignition on. If scan tool does not display BUS SHORT TO 5 VOLTS,
replace instrument cluster circuit board. If scan tool displays BUS
SHORT TO 5 VOLTS, go to next step.
4) Turn ignition off. Disconnect compass mini-trip computer.
Turn ignition on. If scan tool does not display BUS SHORT TO 5 VOLTS,
replace compass mini-trip computer. If scan tool displays BUS SHORT TO
5 VOLTS, go to next step.
5) Turn ignition off. Disconnect CCD radio. Turn ignition on.
If scan tool does not display BUS SHORT TO 5 VOLTS, replace radio. If
scan tool displays BUS SHORT TO 5 VOLTS, go to next step.
6) Turn ignition off and wait 2 minutes. Disconnect Air Bag
Control Module (ACM). ACM is located under center of instrument panel.\
Turn ignition on. If scan tool does not display BUS SHORT TO 5 VOLTS,
replace ACM. If scan tool displays BUS SHORT TO 5 VOLTS, go to next
step.
7) Turn ignition off. Disconnect Central Timer Module (CTM).\
CTM is mounted behind right corner of dash, beside glove box. Turn

ignition on. If scan tool does not display BUS SHORT TO 5 VOLTS,
replace CTM. If scan tool displays BUS SHORT TO 5 VOLTS, go to next
step.
8) Disconnect scan tool from DLC. Using external voltmeter,
measure voltage between ground and DLC connector terminal No. 3
(Violet/Brown wire). If voltage is more than 4 volts, repair
Violet/Brown wire for short to voltage. If voltage is 4 volts or less,
go to next step.
9) Measure voltage between ground and DLC connector terminal
No. 11 (White/Black wire). If voltage is more than 4 volts, repair
White/Black wire for short to voltage. If voltage is less than 4
volts, replace scan tool cable or scan tool as necessary.
10) Turn ignition off. Using external ohmmeter, measure
resistance between Powertrain Control Module (PCM) connector C3
terminal No. 30 (Violet/Brown wire) and connector C1 terminal No. 17
(Violet/Black wire). PCM is located at right inner fender. If
resistance is less than 800 ohms, repair short between Violet/Brown
wire and Violet/Black wire. If resistance is 800 ohms or more, go to
next step.
11) Measure resistance between PCM connector C3 terminal No.
28 (White/Black wire) and PCM connector C1 terminal No. 17
(Violet/Black wire). If resistance is less than 800 ohms, repair short\
between Violet/Black and White/Black wires of both connectors. See
wiring diagram for clarification. If resistance is 800 ohms or more,
replace PCM.
BUS SHORT TO BATTERY
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Turn ignition off. Disconnect Powertrain Control Module
(PCM). PCM is mounted in right side of firewall. Turn ignition on. If
scan tool does not display BUS SHORT TO BATTERY, go to step 10). If
scan tool displays BUS SHORT TO BATTERY, go to next step.
2) Turn ignition off. Disconnect instrument cluster. Turn
ignition on. If scan tool does not display BUS SHORT TO BATTERY,
replace instrument cluster. If scan tool displays BUS SHORT TO
BATTERY, go to next step.
3) Turn ignition off. Disconnect compass mini-trip computer.
Turn ignition on. If scan tool does not display BUS SHORT TO BATTERY,
replace compass mini-trip computer. If scan tool displays BUS SHORT TO
BATTERY, go to next step.
4) Turn ignition off. Disconnect CCD radio. Turn ignition on.
If scan tool does not display BUS SHORT TO BATTERY, replace radio. If
scan tool displays BUS SHORT TO BATTERY, go to next step.
5) Turn ignition off and wait 2 minutes. Disconnect Air Bag
Control Module (ACM). ACM is located under center of instrument panel.\
Turn ignition on. If scan tool does not display BUS SHORT TO BATTERY,
replace ACM. If scan tool displays BUS SHORT TO BATTERY, go to next
step.
6) Turn ignition off. Disconnect Central Timer Module (CTM).\
CTM is located under left side of instrument panel. Turn ignition on.
If scan tool does not display BUS SHORT TO BATTERY, replace CTM. If
scan tool displays BUS SHORT TO BATTERY, go to next step.
7) Turn ignition off. Disconnect anti-lock brake controller
module. Controller module is mounted to top of ABS hydraulic unit.
Turn ignition on. If scan tool does not display BUS SHORT TO BATTERY,
replace anti-lock brake controller module. If scan tool displays BUS

SHORT TO BATTERY, go to next step.
8) Disconnect scan tool from DLC. Using external voltmeter,
measure voltage between ground and DLC connector terminal No. 3
(Violet/Brown wire). If voltage is more than .2 volt, repair
Violet/Brown wire for short to voltage. If voltage is .2 volt or less,
go to next step.
9) Measure voltage between ground and DLC connector terminal
No. 11 (White/Black wire). If voltage is more than .2 volt, repair
White/Black wire for short to voltage. If voltage is less than .2
volt, replace scan tool cable or scan tool as necessary.
10) Turn ignition off. Using external ohmmeter, measure
resistance between ground and Powertrain Control Module (PCM)
connector C1 terminal No. 31 (Black/Tan wire). PCM is located at right\
inner fender, at corner of firewall. If resistance is less than 10
ohms, go to next step. If resistance is 10 ohms or more, repair open
Black/Tan wire.
11) Measure resistance between ground and PCM connector C1
terminal No. 32 (Black/Tan wire). If resistance is less than 10 ohms,
replace PCM. If resistance is 5 ohms or more, repair open Black/Tan
wire.
BUS SHORT TO GROUND
NOTE: For connector terminal identification and wiring diagrams,
see BODY CONTROL COMPUTER - INTRODUCTION article. Perform
VERIFICATION TEST VER-1 after each repair.
CAUTION: Always turn ignition off prior to disconnecting any module
connector.
1) Turn ignition off. Disconnect Powertrain Control Module
(PCM). PCM is mounted in right side of firewall. Turn ignition on. If
scan tool does not display BUS SHORT TO GROUND, replace PCM. If scan
tool displays BUS SHORT TO GROUND, go to next step.
2) Turn ignition off. Disconnect anti-lock brake controller
module. Controller module is mounted to top of ABS hydraulic unit.
Turn ignition on. If scan tool does not display BUS SHORT TO GROUND,
replace anti-lock brake controller module. If scan tool displays BUS
SHORT TO GROUND, go to next step.
3) Turn ignition off. Disconnect instrument cluster. Turn
ignition on. If scan tool does not display BUS SHORT TO GROUND,
replace instrument cluster circuit board. If scan tool displays BUS
SHORT TO GROUND, go to next step.
4) Turn ignition off. Disconnect compass mini-trip computer.
Turn ignition on. If scan tool does not display BUS SHORT TO GROUND,
replace compass mini-trip computer. If scan tool displays BUS SHORT TO
GROUND, go to next step.
5) Turn ignition off. Disconnect CCD radio. Turn ignition on.
If scan tool does not display BUS SHORT TO GROUND, replace radio. If
scan tool displays BUS SHORT TO GROUND, go to next step.
6) Turn ignition off and wait 2 minutes. Disconnect Air Bag
Control Module (ACM). ACM is located under center of instrument panel.\
Turn ignition on. If scan tool does not display BUS SHORT TO GROUND,
replace ACM. If scan tool displays BUS SHORT TO GROUND, go to next
step.
7) Turn ignition off. Disconnect Central Timer Module (CTM).\
CTM is located under left side of instrument panel. Turn ignition on.
If scan tool does not display BUS SHORT TO GROUND, replace CTM. If
scan tool displays BUS SHORT TO GROUND, go to next step.
8) Disconnect scan tool from DLC. Using external ohmmeter,
measure resistance between ground and DLC connector terminal No. 3
(Violet/Brown wire). If resistance is less than 700 ohms, repair
Violet/Brown wire for short to ground. If resistance is 700 ohms or