GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2003 🢒 VUE - AWD 🢒 Engine 🢒 Engine Controls - 2.2L (L61) 🢒 DTC P1639

Circuit Description

The engine control module (ECM) uses the 5-volt reference 2 circuit as a sensor feed to the following sensors:

    • The manifold absolute pressure (MAP) sensor
    • The accelerator pedal position (APP) 1 sensor
    • The throttle position (TP) 2 sensor

If the ECM detects the voltage on the 5-volt reference 2 circuit is outside a valid range, DTC P1639 sets.

Conditions for Running the DTC
    • The ignition is ON.
    • DTCs P0601, P0602, P0604, P0606, P1621 are not set.

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-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 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 Intermittent Conditions

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

Did you find and correct a condition?

--

Go to Step 12

Go to Step 4

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

Is the voltage within the specified range?

4.8-5.2 V

Go to Intermittent Conditions

Go to Step 10

7
  1. Monitor the DMM while disconnecting all other devices connected to 5-volt reference circuit 2, 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 2 for a short to ground or a short to any sensor low reference circuit. Refer to Wiring Repairs in Wiring Systems.

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. Inspect the following circuits for a short to voltage:
    5. • The MAP sensor signal circuit
    • The accelerator pedal position (APP) 1 sensor signal circuit
    • The throttle position (TP) 2 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 in Wiring Systems.

Did you find and correct a condition?

--

Go to Step 12

Go to Step 11

10

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

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the ECM. Refer to Engine Control Module Replacement .

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

System OK