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.

Schematic Reference

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Scan Tool Data List

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

⇒	If greater than 1 ohm, test the ground circuit for an open/high resistance.

3. Ignition ON, verify a test lamp illuminates when connected between the ignition 1 voltage circuit 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, replace the PCM.

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 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.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.