GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1996 🢒 Chevy G Van 🢒 Engine 🢒 Engine Controls - 6.5L 🢒 DTC P0236 Turbocharger Boost System Performance

Object Number: 52968 Size: MF
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM operates a solenoid to the control boost. This solenoid is normally open. By providing a ground path, the PCM energizes the solenoid which then allows a vacuum to pass to the wastegate valve. During normal operation, the PCM compares the wastegate duty cycle signal with the boost signal and makes corrections in the duty cycle accordingly. This is a type B DTC.

Conditions for Setting the DTC
    • The engine speed greater than 2400 RPM.
    • The fuel rate is greater than 20 mm.
    • The boost pressure is greater than, less than, or equal to 20 kPa from desired (internal to PCM).
    • The conditions were met for 10 seconds.

or

    • The engine speed is greater than 1800 but less than 2400 RPM.
    • The fuel rate is greater than 20 mm.
    • The conditions were met for 12 seconds.

Action Taken When the DTC Sets
    • Poor performance
    • Reduce maximum fuel.
    • No TCC

Conditions for Clearing the MIL/DTC
    • The PCM will turn the MIL OFF after three consecutive trips without a fault condition.
    • A History DTC will clear after forty consecutive warm-up cycles during which the diagnostic does not fail (the coolant temperature has risen 5°C (40°F) from the start up coolant temperature and the engine coolant temperature exceeds 71°C (160°F) during that same ignition cycle).
    • Use of a Scan Tool will clear the DTC codes.

Diagnostic Aids

A vacuum leak or a pinched vacuum line may cause a DTC P0236. Check all of the vacuum lines and the components connected to the hoses for any leaks or sharp bends. Check the vacuum source. Also check for a proper vacuum line routing.

The turbocharger actuator uses a pulse width modulated vacuum solenoid that causes the vacuum to fluctuate under normal conditions. A steady vacuum reading indicates a restricted solenoid vent filter or a solenoid vent orifice.

Test Description

The number(s) below are the Step number(s) on the Diagnostic Table.

  1. This will check the wastegate solenoid and the filter. A plugged filter will not allow the solenoid to vent, which will cause an overboost condition.

    2.

  2. This step checks the turbocharger wastegate actuator for vacuum leaks. The actuator must hold a vacuum.

    3.

  3. This step will check for vacuum leaks at the lines.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the scan tool Capture Info in order to record the Freeze Frame and the failure records for reference, as the data will be lost when the Clear Info function is used.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P1656 set?

--

Go To DTC P1656 Wastegate Solenoid Control Circuit

Go to Step 3

3
  1. Disconnect the vacuum line at the turbocharger wastegate actuator.
  2. Install a vacuum gauge in place of the turbocharger wastegate actuator.
  3. Start the engine.
  4. Observe the vacuum at idle.

Is the vacuum greater than or equal to the specified value (vacuum will fluctuate)?

15 in Hg

Go to Step 4

Go to Step 6

4

  1. Disconnect the wastegate solenoid electrical connector with the engine still running.
  2. The vacuum gauge is still in place.
  3. Observe the vacuum gauge at the idle.

Is the vacuum greater than the specified value?

1 in Hg 

Go to Step 10

Go to Step 5

5
  1. Turn the engine OFF.
  2. Connect a hand held vacuum pump to the turbocharger wastegate actuator.
  3. Apply 5 in. Hg. of vacuum.

Does the turbocharger wastegate actuator hold vacuum?

--

Go to Step 7

Go to Step 12

6
  1. Check all of the vacuum lines from the vacuum pump to the turbocharger wastegate actuator for the following:
    2. • Leaks
    • Deformities
    • Pinches
  2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 13

Go to Step 9

7
  1. Verify the engine is OFF.
  2. Disconnect all of the vacuum lines to the wastegate actuator.
  3. Grip the wastegate actuator rod with a pair of pliers.
  4. Attempt to move the rod back and forth (refer to Engine Mechanical for further testing).

Does the turbocharger wastegate actuator rod move freely?

--

Go to Step 8

Go to Step 12

8

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If any additional DTCs are stored, refer to those tables.

Are there any additional DTCs stored?

--

Go to the Applicable DTC Table

Go to Diagnostic Aids

9

Check the vacuum pump for proper output (refer to Engine Mechanical).

Is the action complete?

--

Go to Step 13

--

10

Check for a plugged wastegate solenoid filter.

Is the wastegate solenoid filter plugged?

--

Go to Step 13

Go to Step 11

11

Replace the wastegate solenoid.

Is the action complete?

--

Go to Step 13

--

12

Replace the turbocharger wastegate actuator.

Is the action complete?

--

Go to Step 13

--

13
  1. Use the Scan Tool in order to select DTC, Clear Info.
  2. Start the engine.
  3. Allow the engine to idle at the normal operating temperature.
  4. Select DTC, Specific, then enter the DTC number which was set.
  5. Operate the until the scan tool indicates that the diagnostic Ran.

Does the Scan Tool indicate that this diagnostic Passed?

--

Go to Step 14

Go to Step 2

14

Use the Scan Tool in order to select Capture Info, Review Info.

Are there any DTCs displayed that have not been diagnosed?

--

Go to the Applicable DTC Table

System OK