Circuit Description
The powertrain control module (PCM) provides 5 volts to the air conditioning (A/C) refrigerant pressure sensor and the manifold absolute pressure (MAP) sensor. 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
Conditions for Setting the DTC
The 5-volt reference 2 voltage is more than 4.7 volts or less than 4.4 volts for longer than 10 seconds.
This diagnostic runs continuous.
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. |
Diagnostic Aids
| • | If any sensor using a 5-volt bias voltage, such as the intake air temperature (IAT) sensor or fuel sensor, is shorted to voltage, DTC P0641 may set in addition to DTC P0651. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Diagnostic Aids |
3 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 10 | Go to Step 4 |
4 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 10 | Go to Step 5 |
5 | Is the voltage measured in the previous step more than the specified value? | 5.2 V | Go to Step 6 | Go to Step 9 |
6 |
Is the voltage more than the specified value? | 0 V | Go to Step 7 | Go to Step 8 |
7 | Test the 5-volt reference circuit for a short to voltage. Refer to Circuit Testing in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | -- |
8 | Test the 5-volt reference circuit for a short to any other circuit within the harness to the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
9 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
10 | Replace the affected sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning, or Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
