P0234-TURBOCHARGER OVERBOOST CONDITION

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the engine running and the ECM attempting to govern turbocharger boost pressure.
Set Condition:
The Boost Pressure Sensor indicates actual turbocharger boost is greater than the ECM setpoint for engine boost for 0.71 second.

Possible Causes

INTERMITTENT DTC

CLOGGED AIR FILTER

INTAKE/EXHAUST RESTRICTION

INTAKE AIR LEAK

BOOST PRESSURE SERVO MOTOR

TURBOCHARGER

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

Diagnostic Test

1. CHECK FOR ACTIVE DTC

Turn the ignition on.
With the scan tool, Clear DTCs in the Engine Control Module (ECM).
Test drive the vehicle.
With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Go To 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2. CHECK THE AIR FILTER

Turn the ignition off.
Remove and inspect the Air Filter for soiling or excessive dirt and debris which may cause air flow restriction.

Were any of these problems found?

Yes

Replace the Air Filter element

Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 3

3. AIR RESTRICTION

NOTE: Inspect all air intake, crankcase vent, charge air cooler and turbocharger related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.

NOTE: Inspect the exhaust system and related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.

Inspect the intake system, exhaust system and related tubes and connections.

Were any problems found?

Yes

Repair or replace as necessary.

Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 4

4. CHECK FOR INTAKE SYSTEM AIR LEAKS

Remove the Crankcase Vent Heater.
Remove the Mass Air Flow Sensor from the turbocharger inlet tube.
Seal off and/or plug the turbocharger inlet tube where the MAF sensor was removed.
Connect smoke machine 84–04 to the Crankcase Vent Heater port in the intake duct and begin injecting smoke into the intake system.
Observe all intake system components for evidence of smoke leakage.

Is there evidence of smoke leakage?

Yes

Repair or replace as necessary.

Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go to 5

5. REPLACE THE BOOST PRESSURE SERVO MOTOR

Replace the Boost Pressure Servo Motor in accordance with the Service Information.

NOTE: Ensure the Boost Pressure Servo Motor and ECM harness connectors are connected.

Test drive the vehicle.
With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Replace the Turbocharger assembly in accordance with the Service Information.

Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Test complete.
Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - STANDARD PROCEDURE)