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For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2006 🢒 VUE - FWD 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P0641

Circuit Description

The engine control module (ECM) uses the 5-volt reference 1 circuit as a sensor feed to the following sensors:

    • The A/C pressure sensor
    • The throttle position (TP) 1 sensor
    • The accelerator pedal position (APP) 2 sensor
    • The fuel tank pressure (FTP) sensor

If the ECM detects the voltage on the 5-volt reference 1 circuit is outside a valid range, DTC P0641 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0641 5-Volt Reference 1 Circuit

Conditions for Running the DTC
    • The ignition is ON, Accessory, or Crank.
    • DTCs P0601, P0602, P0604, P0606, P060D, P060E, P062F, P1621 are not set.
    • DTC P0641 runs continuously when the above conditions are met.

Conditions for Setting the DTC
    • The ECM detects the voltage on the 5-volt reference 1 circuit is less than 4.88 volts or greater than 5.13 volts.
    • The above condition is present for longer than 0.5 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.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for at least 90 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections

3
  1. Visually and physically inspect the engine control module (ECM) and the engine grounds. Ensure that the grounds are clean and secure.
  2. If a condition is found, repair as necessary. Refer to Wiring Repairs .

Did you find and correct a condition?

--

Go to Step 12

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Disconnect the A/C pressure sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the 5-volt reference circuit of the A/C Pressure sensor and a good ground with a DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 6

Go to Step 5

5

Is the voltage more than the specified value?

5.2 V

Go to Step 9

Go to Step 7

6
  1. Connect the A/C pressure sensor electrical connector.
  2. Disconnect the throttle position sensor.
  3. Measure the voltage between the 5-volt reference 1 circuit of the throttle position sensor 1 and a good ground with a DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 10

7
  1. Monitor the DMM while disconnecting all other devices connected to 5-volt reference circuit 1, one at a time.
  2. If voltage changes when one of the above components are disconnected, replace the component. Refer to the appropriate replacement procedure.

Was a component replaced?

--

Go to Step 12

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test the 5-volt reference circuit 1 for a short to ground or a short to any sensor low reference circuit.
  4. If a condition is found, repair as necessary. Refer to Wiring Repairs .

Did you find and correct a condition?

--

Go to Step 12

Go to Step 11

9
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the following circuits for a short to voltage:
    5. • The accelerator pedal position (APP) 2 sensor signal circuit
    • The A/C pressure sensor signal circuit
    • The throttle position (TP) 1 sensor signal circuit
    • The fuel tank pressure (FTP) sensor signal circuit
    • The 5-volt reference circuit for all sensors listed above.
  5. If a condition is found, repair as necessary. Refer to Wiring Repairs .

Did you find and correct a condition?

--

Go to Step 12

Go to Step 11

10

Replace the A/C pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the ECM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for at least 90 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

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?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK