Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit/System Verification
2008 Pontiac Grand Prix BaseSECTION Circuit/System Verification
WARNING: This page is about a different car, the 2008 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition ON. Measure and record the voltage at the battery terminals. Verify that the battery voltage is 11-15 volts. Repeat with the engine running.
- If the battery voltage is not within the specified range, go to Charging System Test .
- Engine running. Observe the scan tool Ignition 1 Signal parameter in the ECM data list. Verify that the scan tool displays a value that is within 2 volts of the battery voltage recorded in step 1.
- If the scan tool parameter is not within the specified range, replace the ECM.
- Go to Diagnostic Aids.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.