P0641

DTC P0641

CIRCUIT DESCRIPTION
The engine control module (ECM) provides 5 volts to the following sensors:
- The manifold absolute pressure (MAP) sensor
- The engine oil pressure (EOP) sensor
- The fuel tank pressure (FTP) sensor
- The air conditioning (A/C) refrigerant pressure sensor
- The accelerator pedal position (APP) sensor 2
- The camshaft position (CMP) sensor (2006 Corvette and Cadillac CTSv 6.0 only)

These 5-volt reference circuits are independent of each other outside the ECM, but are bussed together inside the ECM. Therefore a circuit condition on one sensor 5-volt reference circuit may affect the other sensor 5-volt reference circuits. The ECM monitors the voltage on the 5-volt reference circuit. If the ECM detects that the voltage is out of tolerance, DTC P0641 sets.

DTC DESCRIPTOR
The diagnostic procedure supports the following DTC:
DTC P0641 5-Volt Reference 1 Circuit

CONDITIONS FOR RUNNING THE DTC
- The ignition switch is in the ACC, ON, or Start position.
- The ignition voltage is more than 5.23 volts.
- DTC P0641 runs continuously when the above conditions are met.

CONDITIONS FOR SETTING THE DTC
The ECM detects a voltage out of tolerance condition on the 5-volt reference circuit for more than 0.5 second.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
- The control module commands the TAC system to operate in the Reduced Engine Power mode.
- A message center or an indicator displays Reduced Engine Power.
- Under certain conditions the control module commands the engine OFF.

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 9:

Step 10 - Step 14:

The number below refers to the step number on the diagnostic table.
9. A short to voltage on the signal circuit of the FTP sensor will backfeed through the sensor into the 5-volt reference circuit and set this DTC.