The engine control module (ECM) controls boost pressure by a pulse-width ground signal to the boost control solenoid. The boost control solenoid is normally an open valve. Under most conditions, the ECM commands the boost control solenoid to operate at 99-100 percent duty cycle. This keeps the solenoid valve closed and allows only inlet vacuum to control the position of the bypass valve. At idle, engine vacuum is applied to the upper side of the bypass valve actuator, counteracting spring tension to hold the bypass valve open. As engine load is increased, engine vacuum is decreased, causing the spring in the bypass valve actuator to overcome the applied vacuum, closing the bypass valve and allowing the boost pressure to increase. The bypass valve starts to close when the vacuum measures 250 mm Hg (10 in Hg) and is fully closed at 90 mm Hg (3.5 in Hg). When reduced boost pressure is desired, the ECM commands the boost control solenoid to operate at a 0 percent duty cycle, but may command a partial duty cycle, approximately 62 percent, depending on the operating condition. This opens the solenoid valve and allows boost pressure to enter the bypass valve actuator at the lower side to counteract the spring tension, opening the bypass valve and re-circulating excess boost pressure back into the supercharger inlet. Refer to Boost Control System Diagnosis for further information.

DTC P2261 is a Type B DTC.

DTC P2261 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 35555 Metal Mityvac

1. If DTCs P0069, P0101, P0106, P0107, P0108, P012B, P012C, P012D, P0641, P0651, P2227 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
2. Ignition ON, observe the BARO, MAP, and SC Inlet Pressure parameters. All 3 sensor kPa values should be within 5 kPa of each other and also the actual barometric pressure (BARO). Determine the altitude for your area and compare the parameters to the range specified in the altitude vs. barometric pressure table. Refer to Altitude Versus Barometric Pressure .

Caution: Refer to Road Test Caution in the Preface section.

3. Engine running, on a road test perform a brief wide open throttle (WOT) acceleration from a stop. The MAP sensor parameter on the scan tool should increase rapidly. This increase should be from approximately 35 kPa at idle to more than 135 kPa.
4. Ignition OFF, inspect for the following conditions:

•	The vacuum lines for any cracking, loose fit, and for the proper connections at the following:

-	The bypass valve actuator

-	The bypass valve solenoid

-	The supercharger intake plenum

•	The bypass valve actuator for sticking or damage

•	The boost control solenoid for damage

•	The bypass valve lever for damage

•	The bypass valve cable for sticking, binding, out of adjustment, or damage--Refer to Supercharger Cleaning and Inspection .

5. Engine running, observe the DTC information with a scan tool. DTC P2261 should not set.
6. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Important: You must perform the Circuit System Verification before proceeding with Circuit/System Testing.

1. Disconnect the inlet vacuum signal hose from the bypass valve actuator.
2. Connect a vacuum gage to the inlet vacuum signal hose.
3. Engine running, observe the vacuum gage. The reading should be more than 15 in Hg.

⇒	If the vacuum is more than 15 in Hg, refer to Boost Control System Diagnosis .

4. Disconnect the boost signal hose from the bypass valve actuator.
5. Connect a vacuum gage to the boost signal hose.
6. Start and idle the engine in Park. Observe the vacuum gage. The reading should be 0 in Hg.

⇒	If the vacuum is more than 0 in Hg, inspect for the following conditions:

•	An out of adjustment bypass cable

•	A broken bypass cable

•	A bent or damaged cable bracket

•	Refer to Supercharger Cleaning and Inspection for additional information on any of the above conditions.

7. Ignition OFF, connect the J 35555 to the inlet vacuum signal port on the bypass valve actuator. Slowly apply vacuum to the valve while observing the bypass actuator. The bypass actuator rod should retract.

⇒	If the bypass actuator rod does not retract, disconnect the actuator from the bypass cable and apply vacuum to the actuator. If the actuator still does not retract, replace the actuator.

⇒	If the actuator valve retracts after disconnecting the bypass cable, remove the supercharger and throttle body. Inspect the bypass cable and valve for a binding condition or a disconnected bypass valve. Refer to Supercharger Cleaning and Inspection .

Caution: Refer to Road Test Caution in the Preface section.

8. Engine running, on a road test take a snapshot of the induction data list while depressing the accelerator pedal briefly to WOT, then releasing the throttle to the at rest position. Exit from the snapshot and review the data. Refer to Scan Tool Snapshot Procedure . The MAP sensor parameter on the scan tool should increase rapidly. This increase should be from approximately 35 kPa at idle to more than 130 kPa.

⇒	If the MAP sensor parameter does not increase, remove the supercharger and throttle body. Inspect the bypass cable and brackets for the following conditions:

•	A broken bypass cable

•	A bent or damaged cable bracket--Refer to Supercharger Cleaning and Inspection for any of the above conditions.

1. Ignition OFF, disconnect the top vacuum hose at the bypass actuator.
2. Connect a vacuum gage to the actuator. Apply 10 in Hg to the actuator. The actuator should retract and hold vacuum for at least 15 seconds.

⇒	If the actuator does not hold vacuum, replace the actuator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.