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P168C




DTC P168C or P168D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptor
DTC P168C
- Turbocharger Boost Control Position Slow Response - Increasing Position

DTC P168D
- Turbocharger Boost Control Position Slow Response - Decreasing Position

Circuit/System Description

The position of the turbocharger vanes is controlled by the engine control module (ECM). The ECM utilizes a turbocharger vane control solenoid valve to control the turbocharger vanes, and a turbocharger vane position sensor to verify the position of the vanes. The ECM will vary the boost dependent upon the load requirements of the engine. The turbocharger vane position sensor provides the ECM with a signal voltage relative to the vane position.

Conditions for Running the DTC

* DTC P0045, P0047, P0048, P006E, P007C, P007D, P008F, P0117, P0118, P02E8, P02E9, P0401, P0402, P128E, P140B, P140C, P16A0, P16A1, P16A2, P2228, or P2229 is not set.
* The coolant temperature is greater than 70°C (158°F).
* The engine speed is between 1,000-1,800 RPM.
* The barometric pressure (BARO) is greater than 74.8 kPa (10.85 psi).
* The ambient air temperature is greater than -7°C (19.4°F).
* The throttle position is less than 5 %.
* The turbocharger actuator position sensor offset learning is not active.
* The turbocharger vane cleaning/ wiping, procedure is not active.
* DTC P168C and P168D run continuously whenever the above conditions are met.

Conditions for Setting the DTC

The ECM detects that the difference between actual vane position and desired vane position, over a specified amount of time, is greater than a calibrated threshold.

Action Taken When the DTC Sets

DTC P168C and P168D are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P168C and P168D are Type B DTCs.

Diagnostic Aids

A restricted oil supply feed to the turbocharger may cause this DTC to set.

Reference Information
Schematic Reference

Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)
Description and Operation

Turbocharger System Description Description and Operation
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, observe the scan tool DTC information. Verify DTC P003A, P0045, P0047, P0048, P006E, P006F, P06D2, P2263, P2564, P2565, P2598 or P2599 is not set.

• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Engine running, observe the scan tool TC Vane Position Sensor and the Desired TC Vane Position parameters. Increase the TC Vane Position Sensor in 5 % increments from 0-100 % within 20 s then decrease the TC vane position sensor in 5 % increments from 100-0 % within 20 s. The parameters should increase and decrease smoothly and remain within 2 % throughout the entire commanded range.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

1. Inspect the turbocharger for debris, sticking vanes or damage. Refer to Turbocharger Cleaning and Inspection 79. Turbocharger Cleaning and Inspection.

• If a condition is found, clean or replace the turbocharger as necessary.

2. Inspect the Q41 turbocharger vane position control solenoid valve and B112 turbocharger vane position sensor for damage or sticking.

• If a condition is found, test or replace the affected component as necessary.

Component Testing

Turbocharger Vane Position Control Solenoid Valve
1. Ignition OFF, disconnect the harness connector at the Q41 turbocharger vane position control solenoid valve.
2. Measure the resistance across the Q41 turbocharger vane position control solenoid valve terminals. The resistance should be between 3-7 ohm.

• If greater than the specified range, replace the Q41 turbocharger vane position control solenoid valve.

3. Test for infinite resistance between each Q41 turbocharger vane position control solenoid valve terminal and the solenoid valve housing.

• If less than the specified range, replace the Q41 turbocharger vane position control solenoid valve.

4. Ignition OFF, remove the turbocharger vane position control solenoid valve.
5. Connect the Q41 turbocharger vane position control solenoid valve harness connector.
6. Ignition ON, command the TC Vane Pos. Cntrl. Solenoid ON with a scan tool. Depress and hold the CAM follower slightly at the tip of the TC solenoid valve while observing the slot closest to the CAM follower for the spool valve to move to the open position.

• If the spool valve did not move to the open position, replace the Q41 turbocharger vane position control solenoid valve.

Turbocharger Vane Position Sensor
1. Remove the B112 turbocharger vane position sensor.
2. Connect the B112 turbocharger vane position sensor harness connector.

Note: It is normal for the TC Vane Position Sensor voltage to quickly return to approximately 4.9 V as the plunger reaches its fully depressed position.

3. Ignition ON, observe the scan tool TC Vane Position Sensor voltage while slowly depressing the plunger at the end of the B112 turbocharger vane position sensor. The voltage should decrease smoothly from approximately 4.9-0.2 V.

• If the TC Vane Position Sensor parameter drops out or spikes, replace the B112 turbocharger vane position sensor.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Turbocharger Replacement (LGH) Turbocharger Replacement (LGH)Turbocharger Replacement (LML) Turbocharger Replacement (LML)
* Turbocharger Control Solenoid Valve Replacement Turbocharger Control Solenoid Valve Replacement
* Turbocharger Vane Position Sensor Replacement Turbocharger Vane Position Sensor Replacement
* If any service has been performed on the turbocharger or on the turbocharger components, a turbocharger relearn must be performed. Refer to Turbocharger Learn Testing and Inspection.
* Control Module References Control Module References for ECM replacement, setup, and programming

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