DTC P0236 Turbocharger Boost System Performance. GMC Truck GMC Suburban

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 2WD 🢒 Engine 🢒 Engine Controls - 6.5L 🢒 DTC P0236 Turbocharger Boost System Performance

Engine Controls Components
Engine Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

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

Conditions for Running the DTC

•	The PCM performs this DTC diagnostic continuously.

•	The engine speed is more than 2400 RPM.

•	The fuel rate is more than 20 mm.

•	The engine speed is more than 1800 but less than 2400 RPM.

•	The fuel rate is more than 20 mm.

Conditions for Setting the DTC

•	The boost pressure is more than or less than 20 kPa from desired (internal to PCM).

•	All diagnostic conditions 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 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 clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures

•	The use of a scan tool.

Diagnostic Aids

A vacuum leak or a pinched vacuum line may cause a DTC P0236. Check all vacuum lines and components connected to the hoses for leaks or sharp bends. Check vacuum source. A possible EGR DTC will store if there is a problem with the vacuum source. Also check for proper vacuum line routing.

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

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

This will check the wastegate solenoid and 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 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 the DTCs, use the scan tool Capture Info to save the Freeze Frame and failure records for reference. The control module's data is deleted once the Clear Info function is used.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to 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

Clear the DTCs.
Disconnect the vacuum line at the turbocharger wastegate actuator.
Install a vacuum gage 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 gage still in place, observe the vacuum at idle.

Is the vacuum greater than the specified value?

1 in. Hg

Go to Step 19

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 21

Check all 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 22

Go to Step 8

Verify the engine is OFF.
Disconnect all 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.

Does the turbocharger wastegate actuator rod move freely?

Go to Step 12

Go to Step 21

Check the vacuum pump for proper output (refer to Engine Vacuum Pump Test in Engine Mechanical).

Was a problem found?

Go to Step 22

Go to Step 9

Disconnect the vacuum supply line to the wastegate solenoid.
Install a vacuum gage on the vacuum supply line.
Start and idle the engine.
Observe the vacuum gage.

Is the vacuum more than the specified value?

15 in Hg

Go to Step 10

Go to Step 16

Turn the engine OFF.
Connect the vacuum line to the wastegate solenoid.
Disconnect the actuator vacuum line at the wastegate solenoid.
Install a vacuum gage on the port of the wastegate solenoid.
Start and idle the engine.
Observe the vacuum gage.

Is the vacuum more than the specified value?

15 in Hg

Go to Step 17

Go to Step 11

Disconnect the wastegate solenoid.
Connect a test lamp between the ignition 1 voltage and control circuits of the wastegate solenoid harness connector.
Start and idle the engine.

Does the test lamp illuminate?

Go to Step 20

Go to Step 14

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 boost pressure?

Go to Step 13

Go to Step 18

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored, refer to those table(s).

Are any additional DTCs stored?

Go to the Applicable DTC Table

Go to Diagnostic Aids

Test the wastegate solenoid ignition 1 voltage circuit for a short to ground or an open. Repair as necessary.

Did you find and correct the condition?

Go to Step 24

Go to Step 15

Test the wastegate solenoid control circuit for an open. Repair as necessary.

Did you find and correct the condition?

Go to Step 24

Go to Step 23

Repair the vacuum leak between the vacuum pump and the wastegate solenoid.

Did you complete the repair?

Go to Step 24

Repair the vacuum leak between the wastegate solenoid and the wastegate actuator.

Did you complete the repair?

Go to Step 24

Replace the boost sensor. Refer to Boost Sensor Replacement .

Is the action complete?

Go to Step 24

Check for a plugged wastegate solenoid filter. Repair as necessary.

Is the wastegate solenoid filter plugged?

Go to Step 24

Go to Step 20

Replace the wastegate solenoid. Refer to Wastegate Solenoid Replacement .

Is the action complete?

Go to Step 24

Replace the turbocharger wastegate actuator.

Is the action complete?

Go to Step 24

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

Is the action complete?

Go to Step 24

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Did you complete the replacement?

Go to Step 24

Using the scan tool, clear the DTCs.
Start the engine.
Allow the engine to idle at normal operating temperature.
Select DTC and the Specific DTC function.
Enter the DTC number which was set.
Operate the vehicle, with the Condition for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

Go to Step 25

Go to Step 2

Does the scan tool display any additional undiagnosed DTCs?

Go to the Applicable DTC Table

System OK