Buffer Output Testing & Diagnosis
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 1991 GMC Pickup, 1991 GMC Cab & Chassis, 1991 GMC C3500 HD, 1991 Chevrolet Pickup, and 1991 Chevrolet Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Before testing BUFFER OUTPUT, perform test for any symptoms found. See SPEEDOMETER/ODOMETER TESTING & DIAGNOSIS .
- Disconnect instrument cluster connector. Turn ignition on. Check for 12 volts between ground and Red/White wire at instrument cluster connector terminal A16. See Fig 1. If 12 volts is present, go to next step. If voltage reading is less than 12 volts, check for open in Red/White wire (cruise control circuit).
- Check for 12 volts between ground and Brown wire at connector terminal B17. If 12 volts is present, replace instrument cluster. If voltage reading is less than 12 volts, check for open in Brown wire circuit. Enter ECM diagnostics if necessary. See G-TESTS W/ CODES - Gasoline or G-TESTS W/ CODES - DIESEL in ENGINE PERFORMANCE.