CAUSE A - IGN VOLTAGE SHORTED TO UNSWITCHED BATTERY SOURCE IN PDM OR PDM/VSM HARNESS
PROCEDURE OR ACTION:
1. Ensure truck power is OFF.
2. At the VSM, disconnect CPS 1.
3. Change DMM to volts scale.
4. At the VSM harness connector, measure the voltage across the DTC indicated switched IGN input wire (+) and
the negative terminal ( ) of the battery.
Is voltage approximately system voltage?
YES: The IGN input is shorted to an unswitched battery source. Go to Step 5.
NO: Go to Cause C.
5. Disconnect the corresponding connector from the PDM. Repeat the measurement in Step 4.
Is voltage approximately system voltage?
YES: The IGN input is shorted to an unswitched battery source within the PDM/VSM harness. Refer to Electrical
Schematic in Diagrams and Schematics 8000 SRM 1152 to identify unswitched voltage sources. Locate and
repair/replace shorted wire/connection. See Wire Harness Repair 2200 SRM 1128.
NO: Go to Step 6.
CAUSE B - IGN VOLTAGE SHORTED TO UNSWITCHED BATTERY SOURCE IN PDM OUTPUT HARNESS
PROCEDURE OR ACTION:
1. Refer to Electrical Schematic in Diagrams and Schematics 8000 SRM 1152 for the following steps.
2. With the DMM connected to the IGN voltage output pin at CPS 1, observe DMM while disconnecting each device
that connects to the indicated IGN source. When voltage goes to zero, identify the relevant harness for that
device.
3. Use DMM to verify localized STB on relevant harness. Locate and repair/replace shorted wire/connection. See
Wire Harness Repair 2200 SRM 1128.
CAUSE C - IGN VOLTAGE SHORTED TO SWITCHED BATTERY SOURCE IN PDM OR PDM/VSM HARNESS
PROCEDURE OR ACTION:
1. Remove the DTC indicated IGN Relay from the PDM.
NOTE: Turning on power with this relay removed will cause a DTC for the removed relay to be displayed on the DSC.
Ignore this new DTC.
2. Turn truck power ON.
3. Change DMM to volts scale.
4. At the relay socket, measure the voltage across socket terminal #87 (+) and the negative terminal ( ) of the
battery.
Is voltage approximately system voltage?
YES: The IGN voltage input is shorted to another switched battery source either in the PDM or another accessory
circuit. Go to Step 5.
NO: Relay contacts #87 and #30 are shorted. Replace relay. See Electrical System 2200 SRM 1142.
5. Ensure truck power is OFF.
6. Disconnect PDM connectors CPS 15 and CPS 16.
7. Turn truck power ON.
8. Repeat the measurement in Step 4.
Is voltage approximately system voltage?
YES: The IGN voltage is shorted to another switched battery source either in the PDM or another accessory
circuit connected to the VSM. Go to Step 9.
NO: The IGN circuit is shorted to another switched battery source in the circuitry connected to CPS 15 and/or
CPS 16. Review schematics for adjacent circuits, trace and isolate the source. See Wire Harness Repair 2200
SRM 1128.
9. Ensure truck power is OFF.
10. Remove indicated IGN output circuit pin from connector CPS 1.