P0651

DTC P0651

CIRCUIT DESCRIPTION




The DTC P0651 5 Volt Reference 2 Circuit diagnostic detects an incorrect voltage on the reference B supply circuit. The powertrain control module (PCM) provides 5 volts to the reference B circuit to the following sensors:
- The accelerator pedal position (APP) sensor 2
- The fuel tank pressure (FTP) sensor
- The exhaust gas recirculation (EGR) sensor
- The automatic transmission input shaft speed (AT ISS) sensor
- The air conditioning (A/C) pressure sensor

These 5-volt reference circuits are independent of each other outside the PCM, but are bussed together inside the PCM. Therefore a short circuit condition on the 5-volt reference of one sensor can affect the operation of the other sensors. 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 DESCRIPTOR
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 when the above condition is met.

CONDITIONS FOR SETTING THE DTC
- The reference 2 circuit voltage is less than 4.8 volts or more than 5.2 volts.
- The above condition is present for at least 2 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL).
- The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE MIL/DTC
- The MIL turns OFF after 3 consecutively passing trips without a fault present.
- A history DTC clears after 40 consecutive warm-up cycles without a fault.
- Perform the scan tool Clear DTC Information function.

TEST DESCRIPTION

Steps 1-9:

Steps 10-18:

The numbers below refer to the step numbers on the diagnostic table.
1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
16. After replacing the PCM a new minimum throttle position and idle speed must also be established.