High Pressure Shutoff Relay Control Circuit -- CNG Engine Only

Name of Code:
High Pressure Shutoff Relay Control Circuit

When Monitored:
with the ignition key on and battery voltage greater than 10 volts.

Set Condition:
An open or shorted condition is detected in the High Pressure Shutoff relay control circuit.

Theory of Operation:
The High Pressure Shutoff relay controls the 12-volt source to the fuel pump (High pressure shutoff solenoid in CNG applications). The relay is located in the power distribution center (PDC). One side of the relay control coil is supplied with 12 volts when the ignition switch is turned to the "run" position. The circuit is completed when the other side of the relay coil is grounded by the powertrain control module (PCM). The PCM grounds the relay when the ignition switch is in either the run or crank position and engine RPM is detected. If engine RPM is not detected, the PCM will remove the High Pressure Shutoff relay control circuit ground.

Possible Causes:
- Relay coil open or shorted
- Fused ignition switch output circuit open
- High Pressure Shutoff relay control circuit is open or shorted
- Inoperative circuit driver in powertrain control module
- Connector terminals
- Connector wires

NOTE: The fuel pump relay is referred to as the high pressure shutoff relay in CNG applications.