Boost Gage Malfunction

Boost Gage Malfunction

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category

Diagnostic Fault Information





Circuit/System Description

The boost gage is a measure of the engine manifold air pressure. The engine control module (ECM) sends a PWM signal to the boost gage via the boost gage signal circuit. The boost gage displays the engine air intake above and below the ambient manifold pressure. The ECM controls the engine boost pressure with the boost control solenoid. The engine boost system pumps more air than the engine would normally use into the intake manifold. The excess air pumped into the intake manifold, creates the engine boost effect. The maximum boost pressure is about 83 kPa (12 psi). When the ignition is turned ON and the boost gage is ON, the boost gage performs a power up self test. The boost gage dial normally below 0 kPa (0 psi) moves up to 0 kPa (0 psi) to indicate the boost gage passed the self test. Power is provided to the boost gage via the ignition 1 voltage circuit.

Reference Information
Schematic Reference

Instrument Cluster Schematics (Instrument Cluster Schematics)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Instrument Cluster Description and Operation (Description and Operation)
* Boost Control System Description ()

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the boost gage.
2. Ignition OFF, test for less than 1 ohm of resistance between the boost gage ground circuit terminal D and ground.

• If greater than the specified range, test the circuit for a short to battery or open/high resistance.

3. Ignition ON, verify a test lamp illuminates when connected between the boost gage B+ circuit terminal A and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Ignition OFF, connect the harness connector at the boost gage.
5. Ignition ON, verify that the boost gage performs a self test by the gage dial moving up to the 0 kPa (0 psi) marker.

• If the boost gage does not perform a self test, test the boost gage signal circuit terminal C for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. If all circuits test normal, replace the boost gage.

Repair Instructions

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

* Supercharger Boost Air Pressure Indicator Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for the ECM replacement, setup, and programming