DTC P0236 Turbocharger Boost System Performance. GMC Truck GMC P62 Commercial Chassis 1997

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1997 🢒 GMC P62 Commercial Chassis 🢒 Engine 🢒 Engine Controls - 6.5L 🢒 DTC P0236 Turbocharger Boost System Performance

Engine Controls Components
Engine Controls (Cell 22: Fuel Controls 4)
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.

Conditions for Setting the DTC

•	The PCM performs this diagnostic continuously.

•	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).

•	All conditions were met for 10 seconds.

•	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 10 seconds.

Action Taken When the DTC Sets

•	A poor performance condition will exist.

•	The PCM will reduce maximum fuel.

•	The PCM will disable the torque converter clutch (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 when forty consecutive warm-up cycles that 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].

•	The use of a scan tool.

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. A possible EGR DTC will store if there is a problem with the vacuum source. Also check for a proper vacuum line routing.

The turbocharger wastegate 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.

This will check the wastegate solenoid and the filter. If the filter is plugged, the filter will not allow the solenoid to vent and this will cause an overboost condition.

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

This step will check for vacuum leaks at the lines.

This step will check for a skewed boost pressure sensor.

Step

Action

Value(s)

Yes

Important: Before clearing any DTCs, use the Scan Tool Capture Info to save freeze frame and failure records for reference, as the Scan Tool loses data when using the Clear Info function.

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

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

Is the DTC P1656 also set?

Go to DTC P1656 Wastegate Solenoid Control Circuit

Go to Step 3

Disconnect the vacuum line at the turbocharger wastegate actuator.
Install a vacuum gauge in place of the turbocharger wastegate actuator.
Start the engine.
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

Disconnect the wastegate solenoid electrical connector with the engine still running.
With the vacuum gauge is still in place, observe the vacuum at the idle.

Is the vacuum greater than the specified value?

1 in Hg

Go to Step 12

Go to Step 5

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

Does the turbocharger wastegate actuator hold vacuum?

Go to Step 7

Go to Step 14

Check all of the vacuum lines from the vacuum pump to the turbocharger wastegate actuator for the following:

•

Leaks

•	Deformities

•

Pinches

If a problem is found, repair as necessary.

Was a problem found?

Go to Step 15

Go to Step 8

Verify the engine is OFF.
Disconnect all of the vacuum lines to the wastegate actuator.
Grip the wastegate actuator rod with a pair of pliers.
Attempt to move the wastegate actuator rod back and forth. Refer to Turbocharger in Turbocharger.

Does the turbocharger wastegate actuator rod move freely?

Go to Step 8

Go to Step 14

Check the vacuum pump for proper output. Refer to Vacuum Pump Diagnosis in Vacuum Pump.

Was a problem found?

Go to Step 15

Go to Step 9

Connect a scan tool.
Start the engine and let the engine idle.
Observe the boost pressure display on the scan tool.
Increase the engine RPM to 1,500 and return the engine to an idle.

Does the scan tool display a change in the boost pressure?

Go to Step 10

Go to Step 11

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

Replace the boost sensor. Refer to Boost Sensor Replacement .

Is this action complete?

Go to Step 16

Check for a plugged wastegate solenoid filter.

Is the wastegate solenoid filter plugged?

Go to Step 16

Go to Step 13

Replace the wastegate solenoid. Refer to Wastegate Solenoid Replacement .

Is the action complete?

Go to Step 16

Replace the turbocharger wastegate actuator. Refer to Wastegate Actuator in Turbocharger.

Is the action complete?

Go to Step 16

Replace the vacuum pump. Refer to Vacuum Pump Replacement in Vacuum Pump.

Is the action complete?

Go to Step 16

Using the Scan Tool, clear the DTCs.
Start engine and idle at normal operating temperature.
Select DTC, Specific, then enter the DTC number which was set.
Operate the vehicle, within the Conditions for Setting this DTC, until the Scan Tool indicates the diagnostic Ran.

Does the Scan Tool indicate the diagnostic Passed?

Go to Step 14

Go to Step 2

Does the Scan Tool display any additional undiagnosed DTCs?

Go to the applicable DTC table

System OK