For 1990-2009 cars

### 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

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage
--- | --- | --- | ---
Ignition 1 Voltage | 1 | 1 | --
Boost Gage Signal | 1 | 1 | --
Boost Gage Ground | -- | 1 | --
1. Boost gage inoperative

### Circuit/System Description

The boost gage is a measure of the engine manifold air pressure. The powertrain control module (PCM) 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 PCM 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 as controlled by the PCM. The boost gage dial 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

• | Engine Controls Schematics

#### Connector End View Reference

• | Displays and Gages Connector End Views

• | Powertrain Control Module Connector End Views

#### Description and Operation

• | Instrument Cluster Description and Operation

• | Boost Control System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Scan Tool Data List

### 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 ground circuit for an open/high resistance.

3. Ignition ON, verify a test lamp illuminates when connected between the boost gage ignition 1 voltage circuit terminal A and ground.

⇒ | If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the BCM.

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) mark.

⇒ | 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 PCM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Supercharger Boost Air Pressure Indicator Replacement

• | Control Module References for the PCM replacement, setup, and programming