GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Savana 🢒 DTC 🢒 DTC P0238

Circuit Description

The powertrain control module (PCM) controls boost using the turbocharger wastegate solenoid. The solenoid is pulse width modulated (PWM). When the wastegate solenoid is not energized, the vacuum to the turbocharger wastegate solenoid is vented to atmosphere through the solenoid. As the pulse width is increased by the PCM, more vacuum is applied through the solenoid to the wastegate actuator. At idle a higher vacuum to the wastegate actuator helps keep the wastegate closed. At higher engine speeds the vacuum supplied by the solenoid is less, allowing the turbocharger boost pressure to overcome the wastegate actuator.

Conditions for Running the DTC

The engine speed is less than 3,506 RPM.

Conditions for Setting the DTC

The boost pressure is more than or equal to 4.8 volts (202 kPa).

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

An intermittent can be caused by the following the following conditions:

    • Faulty connections
    • Rubbed-through wire insulation
    • A broken wire inside the insulation

Check for opens or shorts to ground in the signal wire, or for an open in the 5-volt reference circuit.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step will determine if the PCM is responding to a low signal voltage. This will indicate that the PCM is OK.

    2.

  2. If the scan display is still less than or equal to 9 kPa by disconnecting the PCM the short to voltage is in the wiring.

    3.

  3. If the voltmeter value stays the same by disconnecting the PCM the short to battery voltage is in the wiring.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Important: Before clearing the DTCs, use the scan tool Capture Info function in order to save the Freeze Frame/Failure Records for reference. The control module's data is deleted once the Clear Info function is used.

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Connect a scan tool.
  2. Start the engine and let the engine idle.

Does the scan tool display a boost pressure that is more than or equal to the specified value?

202 kPa (29.30 psi)

Go to Step 3

Go to Step 5

3

  1. Turn OFF the ignition.
  2. Disconnect the boost sensor electrical connector.
  3. Using a fused jumper, jumper the boost sensor signal to the sensor ground.
  4. Turn ON the ignition.

Does the scan tool display a boost pressure that is less than or equal to the specified value?

10 kPa (1.45 psi)

Go to Step 6

Go to Step 4

4
  1. Verify the boost sensor is disconnected.
  2. Turn ON the ignition.
  3. Set the DMM to the mA scale.
  4. Measure the current across the boost sensor signal and at the sensor ground circuit at the harness connector.

Does the current measure less than the specified value?

10 mA

Go to Step 6

Go to Step 11

5
  1. The DTC is intermittent.
  2. If no additional DTCs are stored, refer to Diagnostic Aids.
  3. If additional DTCs are stored, refer to those tables first.

Are any additional DTCs stored?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Diagnostic Aids

6
  1. Turn ON the ignition, with the engine OFF.
  2. Connect the DMM to a known good ground.

    3. Probe the 5-volt reference circuit at the boost sensor harness.

Does the voltage measure more than the specified value?

5.2 V

Go to Step 12

Go to Step 7

7
  1. Verify that the boost sensor is disconnected.
  2. Use a DMM in order to measure the voltage across the boost sensor 5-volt reference circuit to the sensor ground at the harness connector.

Does the voltage measure within the specified range?

4.8-5.2 V

Go to Step 8

Go to Step 13

8
  1. Check for an open or a faulty sensor signal terminal connection at the PCM or the boost sensor.
  2. If you find a problem, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 15

Go to Step 9

9

  1. Check the boost sensor for a restriction.
  2. If you find a problem, repair the circuit as necessary.

Did you complete the repair?

--

Go to Step 15

Go to Step 10

10

Replace the boost sensor. Refer to Boost Sensor Replacement .

Did you complete the replacement?

--

Go to Step 15

--

11
  1. Check for a short to voltage in the boost sensor signal circuit.
  2. If you find a problem is found, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 15

Go to Step 14

12
  1. Check for a short to battery voltage in the boost sensor 5-volt reference circuit.
  2. If you find a problem is found, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 15

Go to Step 14

13
  1. Check for an open or a faulty sensor ground terminal connection at the PCM or the boost sensor.
  2. If you find a problem is found, repair the connection as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

--

Go to Step 15

Go to Step 14

14

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15
  1. Use a scan tool in order clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches a normal operating temperature.
  4. Select the DTC and the Specific DTC functions.
  5. Enter the DTC number that was set.
  6. Operate the vehicle within the Conditions for Setting the DTC until the scan tool indicates the diagnostic ran.

Does the scan tool indicate the diagnostic passed?

--

Go to Step 16

Go to Step 2

16

Does the scan tool display any additional undiagnosed DTCs?

--

Go to Diagnostic Trouble Code (DTC) List

System OK