DTC P1298. Chevrolet Chevrolet T-Series Medium Duty Truck F6/F7/F8 2003

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2003 🢒 Chevrolet T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P1298

Circuit Description

The pressure control (PC) valve is used to adjust the supply pump discharge amount to adjust common rail pressure. The discharge amount from the supply pump to the common rail is determined by continuity timing to the PC valve. The PC valve relay is used to supply an electric current to the PC valve.

Conditions for Setting the DTC

The PC valve driving voltage is abnormal when the ignition is OFF causing the PC valve circuit to turn OFF.

Action Taken When the DTC Sets

•	The control module stores the DTC information into memory when the diagnostic runs and fails.

•	The malfunction indicator lamp (MIL) will illuminate.

Conditions for Clearing the DTC

•	A current DTC Last Test Failed clears when the diagnostic runs and passes.

•	Clear the DTC with a scan tool.

Diagnostic Aids

Inspect for poor connections at the PC valve relay. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Does the DTC set with the ignition ON or with the engine operating?

Go to Step 2

Go to Intermittent Conditions

Turn the ignition OFF.
Disconnect the pressure control (PC) valve harness.
Measure the voltage at the engine control module (ECM) connector between the following points:

•	Between pin number C5-1 and pin number C2-8 of the ECM

•	Between pin number C5-8 and pin number C2-8 of the ECM

Does the voltage measure near the specified value?

12 V

Go to Step 4

Go to Step 3

Temporarily jumper the signal and ground pin together at the PC valve.
Cycle the ignition OFF and ON.

Does the DTC set?

Go to Step 7

Go to Step 8

Remove the PC valve relay.
Measure the resistance between contact point 5 and 1.

Does the resistance measure more than the specified value?

100 M ohms

Go to Step 5

Go to Step 6

Turn the ignition OFF.
Disconnect the PC valve harness from the PC valve, PC valve relay, and the ECM.
Measure the voltage between pin number 1 at the PC valve relay and pin number C2-8 at the ECM .

Does the voltage measure less than the specified value?

1 V

Go to Step 8

Go to Step 6

Replace the PC valve harness or relay.

Did you complete the replacement?

Go to Step 8

Replace the ECM.

Did you complete the replacement?

Go to Step 8

Clear the memory.

Does DTC P1298 set?

Go to Step 2

Go to Step 9

Did any other DTCs set?

Go to Diagnostic Trouble Code (DTC) List

System OK