GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

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

DTC Descriptor

DTC P2261: Turbocharger Bypass Valve Stuck

Circuit/System Description

The turbocharger (TC) incorporates a wastegate that is controlled by a pressure differential, that is determined by the engine control module (ECM) by means of a PWM solenoid valve , in order to regulate the pressure ratio of the compressor. A charge air bypass valve is integrated within the unit, and is also controlled by the ECM by utilizing a remotely mounted solenoid valve to prevent compressor surging and damage from vibrations by opening during abrupt closed throttle conditions. When the bypass valve is commanded open during closed throttle deceleration conditions, the bypass valve allows the air to recirculate in the TC and maintain compressor speed. Within a calibrated range during the closed throttle event, or upon a wide open throttle command, the bypass valve will then close to optimize TC response.

The purpose of this diagnostic is to determine if the charge air bypass valve is stuck closed. The ECM will first verify the integrity of the following sensors. The ECM then compares the actual measured mass air flow to a modeled airflow that is derived from these inputs:

    • The throttle position
    • The engine speed
    • The boost pressure sensor
    • The manifold absolute pressure (MAP) sensor

Conditions for Running the DTC

    • DTCs P0033, P0034, P0035, P0100, P0101, P0102, P0103, P0121, P0122, P0123, P0221, P0222, P0223, P0234, P0236, P0237, P0238, P0299, P2227, P2228, or P2229 is not set.
    • The boost pressure versus the BARO pressure ratio is between 1.1-3.3.
    • The charge air bypass valve has been commanded ON for greater than 1 second immediately after an abrupt closed throttle has occurred and the resulting pressure ratio across the compressor exceeds the calibrated pressure ratio limit.
    • The engine is running.
    • The ignition voltage is between 10-18 volts.
    • The ECM has commanded the bypass valve.
    • The DTCs run continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects that the Bypass valve is stuck in the closed position. The ECM by comparing the measured MAF to the modeled MAF has detected a series of pulsations in the induction system that exceed a calibrated threshold.

Action Taken When the DTC Sets

DTC P2261 is a Type B DTC.

Conditions for Clearing the DTC

DTC P2261 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Turbocharger System Description

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Ignition ON, observe the DTC Information with a scan tool. DTCs P0033, P0034, or P0035 should not set.
  2. If any of the DTCs are set, refer to DTC P0033, P0034, or P0035 for further diagnosis.
  3. Command the Turbocharger Bypass Solenoid Valve ON and OFF with a scan tool. An audible click should be heard and felt.
  4. If the click is not heard or felt, refer to DTC P0033, P0034, or P0035 for further diagnosis.
  5. Engine idling, rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. A valve that is stuck shut will generate an unusual noise. Compare to similar vehicle. There should not be any unusual noise.
  6. If there is unusual noise, refer to Turbocharger Cleaning and Inspection.
  7. 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 for any damage, restrictions, improper routing or connecting of the vacuum hoses on the charge air bypass solenoid valve and the charge air bypass valve.
  2. If a condition is found, repair as necessary.
  3. Clear the DTC and operate the vehicle within the Conditions for Running the DTC.
  4. If the DTC cannot be cleared or continues to reset, then replace the charge air bypass valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Turbocharger Disassemble
    •  Control Module References for engine control module replacement, setup, and programming