Circuit Description
The boost pressure sensor is fixed on the intake manifold. The boost pressure sensor generates voltage according to air pressure in the intake manifold, and the generated voltage is input to the engine control module (ECM) as the boost pressure sensor signal. If the ECM detects a boost pressure sensor signal voltage that is excessively high, this DTC will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0234 Turbocharger Engine Overboost
Conditions for Running the DTC
| • | The engine is running. |
| • | The battery voltage is between 10-16 volts. |
Conditions for Setting the DTC
The ECM detects a high boost pressure signal.
Action Taken When the DTC Sets
| • | The ECM illuminates the malfunction indicator lamp (MIL) and Reduced Engine Power indicator lamp, if fitted, when the diagnostic runs and fails. |
| • | The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records. |
| • | The ECM limits fuel injection quantity for fail-safe operation. |
| • | The ECM closes the exhaust gas recirculation (EGR) valve and stops the EGR control. |
| • | The ECM limits variable nozzle turbocharger (VNT) control solenoid valve operation. |
Conditions for Clearing the DTC
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | If an intermittent condition is suspected, the following may cause an intermittent: |
| - | Poor connections |
| - | A misrouted harness |
| - | Rubbed through wire insulation |
| - | Broken wire inside the insulation |
| • | Inspect for the following conditions: |
| - | Poor connection at ECM--Inspect the harness connectors for the following conditions: |
| • | Backed-out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed or damaged terminals |
| • | Poor terminal to wire connection |
| - | Damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the Engine Coolant Temperature display on the scan tool while moving the connectors and the wiring harness related to the sensor. A change in the display will indicate the location of the fault. |
| • | High resistance is in the boost pressure sensor return circuit may set this DTC. |
| • | Use the scan tool to verify the integrity of the boost pressure sensor signal. Compare the sensor values under all load conditions for an excessively high value. Use the scan tool data list values for nominal sensor readings. |
Step | Action | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||||
2 |
Did the DTC fail this ignition? | Go to Step 3 | Go to Diagnostic Aids | ||||||||||||
3 |
Important: When the engine control module (ECM) detects that the turbocharger is abnormal, the ECM may not recognize a value with the normal boost pressure. Does the DTC set while the ignition is ON or the engine is running? | Go to Step 4 | Go to Intermittent Conditions | ||||||||||||
4 |
Is DTC P0237, P0238, P2007, P2008, P2564, P2565, or P2900 set? | Go to Step 5 | |||||||||||||
5 | Inspect for the following conditions:
Did you complete the action? | Go to Step 6 | -- | ||||||||||||
6 | Inspect for a boost pressure sensor harness short to ground. Did you complete the action? | Go to Step 7 | -- | ||||||||||||
7 |
Did the DTC fail this ignition? | Go to Step 8 | Go to Step 12 | ||||||||||||
8 | Perform the following procedures:
Did you find and correct the condition? | Go to Step 12 | Go to Step 9 | ||||||||||||
9 | Replace the boost pressure sensor assembly. Did you complete the replacement? | Go to Step 12 | -- | ||||||||||||
10 | Inspect for poor connections at the harness connector of the ECM. Did you find and correct the condition? | Go to Step 12 | Go to Step 11 | ||||||||||||
11 |
Important: The new ECM must be programmed. Replace the ECM. Refer to Engine Control Module Programming and Setup , Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming . Did you complete the replacement? | Go to Step 12 | -- | ||||||||||||
12 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 13 | ||||||||||||
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |||||||||||||
