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 Testing
2008 Pontiac Grand Prix BaseSECTION Circuit/System Testing
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 OFF. Disconnect the crank relay. Test for 60-80 ohms between relay terminals 85 and 86.
- If not within the specified range, replace the crank relay.
- Test for less than 1.0 ohm between the relay ground circuit terminal 85 and the negative battery terminal.
- If greater than the specified value, test the ground circuit for an open/high resistance.
- Ignition OFF, connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85. Turn the ignition to the start position. The test lamp should illuminate only when the ignition is held in the start position.
- If the test lamp is always ON, test the control circuit for short to voltage. If the circuit tests normal, replace the ECM.
- If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, replace the relay.
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.