Component Testing

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Relay Test

Ignition OFF, disconnect the RUN/CRANK relay.
Test for 60-180 ohms of resistance between terminals 85 and 86.
- If the resistance is not within the specified range, replace the relay.
Test for infinite resistance between the following terminals:
- 30 and 86
- 30 and 87
- 30 and 85
- 85 and 87
- If less than infinite resistance, replace the RUN/CRANK relay.
Install a 20-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms of resistance between terminals 30 and 87.
- If greater than 2.0 ohms, replace the RUN/CRANK relay.

Switch Test

Ignition OFF, disconnect the stop lamp switch.
With the brake pedal released, measure for infinite resistance between terminals A and B of the switch.
- If resistance is measured, replace the switch.
With the brake pedal released, measure for less than 1.0 ohm resistance between terminals C and D of the switch.
- If resistance is not as specified, replace the switch.
With the brake pedal applied, measure for less than 1.0 ohm resistance between terminals A and B of the switch.
- If resistance is not as specified, replace the switch.
With the brake pedal applied, measure for infinite resistance between terminals C and D of the switch.
- If resistance is measured, replace the switch.