P0651

DTC P0651

Circuit Description

The powertrain control module (PCM) provides 5 volt to the following sensors:

- The air conditioning (A/C) pressure sensor

- The fuel tank pressure (FTP) sensor These 5-volt reference circuits are independent of each other outside the PCM, but are bussed together inside the PCM. Therefore a circuit condition on one sensor 5-volt reference circuit may affect the 0th sensor 5-volt reference circuits. The PCM monitors the voltage on the 5-volt reference circuit. If the PCM detects that the voltage is out of tolerance, DTC P0651 sets.

DTC Descriptors

This diagnostic procedure supports the following DTC. DTC P0651 5 Volt Reference 2 Circuit

Conditions for Running the DTC

- The ignition is ON.

- DTC P0651 runs continuously.

Conditions for Setting the DTC

- The PCM detects that the reference 2 circuit voltage is not equal to the 5-volt supply by more than 0.01 volt.

- The above condition is present for more than 2 seconds.

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 MEL/DTC

- The control module turns OFF the malfunction indicator lamp (MIL L) 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

DTC P0651 Steps 1-3:

DTC P0651 Steps 4-14:

The number below refers to the step number on the diagnostic table.

9. A short to voltage on the signal circuit of the fuel tank pressure (FTP) sensor will backfeed through the sensor into the 5-volt reference circuit and set this DTC.