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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 DTC P0641 5-Volt Reference 1 Circuit diagnostic detects an incorrect voltage on the reference A supply circuit. The powertrain control module (PCM) provides 5 volts to the reference A circuit to the following sensors:

    • The accelerator pedal position (APP) sensor 1
    • The manifold absolute pressure (MAP) sensor
    • The automatic transmission output shaft speed (AT OSS) 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 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.
    • DTC P0641 runs continuously when the above condition is met.

Conditions for Setting the DTC
    • The reference A 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.

Diagnostic Aids

Check for any of the following conditions:

A DTC P0641 can set when water shorts the reference circuit high or low. Inspect for water entry into the sensor or PCM electrical connectors.

An intermittent malfunction may be caused by a fault in the 5-volt reference A electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC P0641 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

Test Description

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.

    2.

  2. After replacing the PCM a new minimum throttle position and idle speed must also be established.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

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. Clear the DTC information with a scan tool.
  3. Turn OFF the ignition for 30 seconds.
  4. Start the engine.
  5. 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.

Does the DTC fail this ignition?

--

Go to Step 3

Go to Diagnostic Aids

3
  1. Turn OFF the ignition.
  2. Disconnect the manifold absolute pressure (MAP) sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 9

Go to Step 4

4

Is the voltage measured in step 3 more than the specified value?

5.2 V

Go to Step 8

Go to Step 5

5
  1. Disconnect the accelerator pedal position (APP) sensor.
  2. Measure again the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with the DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 10

Go to Step 6

6
  1. Disconnect the automatic transmission output shaft speed (AT OSS) sensor.
  2. Measure again the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with the DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 11

Go to Step 7

7
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM).
  3. Test all of the 5-volt reference A circuits for a short to ground. Refer to Circuit Testing .
  4. Repair as necessary. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

8
  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Test all 5-volt reference A circuits for a short to voltage. Refer to Circuit Testing .
  5. Repair as necessary. Refer to Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

9

Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 13

--

10

Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 13

--

11

Replace the AT OSS sensor. Refer to Output Speed Sensor Replacement .

Did you complete the replacement?

--

Go to Step 13

--

12

  1. Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
  2. Perform the idle learn procedure. Refer to Idle Learn .

Did you complete the replacement?

--

Go to Step 13

--

13
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 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 14

14

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