GM Service Manual Online
For 1990-2009 cars only

Sensor/System

Symptoms

Sensor/System

Find the symptom in the left column and perform the test/inspection procedure in the right column, be sure to review each cell of the table to identify all tests for a symptom.

    • Hard Start
    • Surges /Chuggles
    • Hesitation, Sag, Stumble
    • Cuts Out, Misses
    • Poor Fuel Economy
    • Rough, Unstable, or Incorrect Idle and Stalling
    • Backfire
    • Inspect the mass air flow (MAF) sensor for proper installation, obstruction, contamination, and damage. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement.
    • Inspect the MAF sensor for proper seating of the connector and terminals.
    • Inspect the manifold absolute pressure (MAP) sensor for proper installation, obstruction, and damage. Refer to Manifold Absolute Pressure Sensor Replacement.
    • Ensure the quality of the MAP sensor vacuum source.
    • Hard Start
    • Detonation/Spark Knock
    • Hesitation, Sag, Stumble
    • Poor Fuel Economy
    • Rough, Unstable, or Incorrect Idle and Stalling
    • Inspect for vacuum leaks and other unmetered air.
    • Test the engine coolant temperature (ECT) sensor for being shifted in value. Refer to the Temperature Versus Resistance.
    • Surges /Chuggles
    • Lack of Power, Sluggishness, or Sponginess
    • Detonation/Spark Knock
    • Poor Fuel Economy
    • Backfire

Monitor the Knock Sensor (KS) System for excessive spark retard activity. Refer to the Knock Sensor description within in the Electronic Ignition (EI) System Description.

Hesitation, Sag, Stumble

Inspect the accelerator pedal position (APP) sensor and the related wiring.

Inspect the Throttle Actuator Control (TAC) System for proper operation.

    • Surges /Chuggles
    • Lack of Power, Sluggishness, or Sponginess
    • Hesitation, Sag, Stumble
    • Cuts Out, Misses
    • Poor Fuel Economy
    • Rough, Unstable, or Incorrect Idle and Stalling
    • Backfire

Inspect for contaminated oxygen sensor (O2S).

Poor Fuel Economy

Inspect for proper operation of the speedometer. Refer to Symptoms - Instrument Panel, Gages and Console .

    • Hard Start
    • Surges /Chuggles
    • Poor Fuel Economy
    • Rough, Unstable, or Incorrect Idle and Stalling
    • Backfire

Inspect the camshaft actuator for correct operation. Refer to Camshaft Actuator System Description.