P2146

DTC P2146

CIRCUIT DESCRIPTION
The powertrain control module (PCM) opens the AF enable circuit in order to operate on compressed natural gas (CNG). When the AF enable circuit is open the AF fuel mode relay switch is open. The PCM fuel injector pulse width modulated (PWM) signals are routed through the AF injector relays to the fuel injector control module (FICM). The FICM will operate the CNG injectors based upon the PCM pulse width signals. When gasoline operation is desired, the PCM grounds the AF enable circuit. When the AF enable circuit is grounded the AF fuel mode relay closes. The AF fuel mode relay provides a ground path for all of the AF injector relays. The PCM fuel injector PWM signals are routed through the AF injector relays to the gasoline fuel injectors. The PCM controls the AF enable circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The PCM monitors the status of the driver. If the PCM detects an incorrect voltage for the commanded state of the driver, DTC P2146 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P2146 Injector Positive Voltage Relay Control Circuit

CONDITIONS FOR RUNNING THE DTC
- The ignition voltage is between 6-18 volts.
- The engine speed is more than 400 RPM.

CONDITIONS FOR SETTING THE DTC
- The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
- The above condition exists for at least 1 second.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

TEST DESCRIPTION

Step 1 - Step 8:

Step 9 - Step 15:

The numbers below refer to the step numbers on the diagnostic table.
2. This step tests if the concern is active.
4. This step tests if the concern is active only while operating on gasoline. Disconnecting the high pressure lock-off (HPL) solenoid connector will cause a loss of CNG fuel pressure and force a switchover to gasoline. An HPL DTC will set. Reconnect the HPL connector and clear DTC information after all diagnosis and repairs are complete.
5. This step determines if the PCM is receiving 12 volts from the AF fuel mode relay.