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 sensor signal. The boost pressure sensor has the following circuits:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A boost pressure sensor signal circuit |
The ECM supplies 5 volts to the boost pressure sensor on the 5-volt reference circuit. The ECM also provides a ground on the low reference circuit. The boost pressure sensor provides a signal to the ECM on the boost pressure signal circuit which is relative to the pressure changes in the manifold. The ECM should detect a low signal voltage at a low boost pressure, such as low engine load. The ECM should detect high signal voltage at a high boost pressure, such as high engine load. The ECM monitors the boost pressure sensor signals for voltage outside the normal range of the boost pressure sensor. If the ECM detects an excessively high boost pressure sensor signal voltage, this DTC will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0238 Turbocharger Boost Sensor Circuit High Voltage
Conditions for Running the DTC
| • | The ignition switch is ON. |
| • | The battery voltage is between 10-16 volts. |
| • | The engine is not running. |
Conditions for Setting the DTC
The ECM detects that the boost pressure sensor signal voltage is more than 4.95 volts.
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 uses boost pressure 100 kPa. |
| • | The ECM limits the fuel injection quantity for fail-safe operation. |
| • | The ECM limits fuel rail pressure for fail-safe operation. |
| • | The ECM inhibits cruise control. |
Condition 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. |
Step | Action | Values | 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 |
Is DTC P0641 also set? | -- | Go to DTC P0641 | Go to Step 4 | ||||
4 |
Is the Boost Pressure Sensor parameter more than the specified value? | 34 kPa (5 psi) | Go to Step 6 | Go to Step 5 | ||||
5 |
Is the DMM voltage more than the specified range? | 4.5-5.5 V | Go to Step 8 | Go to Step 7 | ||||
6 |
Important: The boost pressure sensor may be damaged if the circuit is shorted to a voltage source.
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||
7 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 | ||||
8 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||
9 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||
10 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||
11 | Replace the boost pressure sensor. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||
12 |
Important: The new ECM must be programmed. Replace the ECM. Refer to, Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 | ||||
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||
