Section 1 (Engine Controls - Tests W/Codes - Diesel)
WARNING: This page does not describe the selected car, but rather 22 other vehicles, including the 1990 GMC Vandura Special, 1990 GMC Vandura, 1990 GMC Value Van, 1990 GMC Suburban, and 1990 GMC Rally Camper Special. However, it is still accessible from the selected car via links, so may be relevant.
- Introduction
- Self-Diagnostic System
- Diagnostic Procedure
- Entering Or Exiting Diagnostic Mode
- Trouble Code Identification
- ECM Location
- Diagnostic Charts
- Notes
- Diagnostic Circuit Check
- Service Engine Soon Light Inoperative
- ECM Check, Service Engine Soon Light On At All Times Or Won't Flash Code 12
- EPR Solenoid Electrical Check
- EPR Vacuum Circuit Check
- Code 12, No Reference Pulse
- Code 14, Coolant Temp Sensor Signal Voltage Low
- Code 15, Coolant Temp Sensor Signal Voltage High
- Code 21, Throttle Position Sensor Signal Voltage High
- Code 22, Throttle Position Sensor Signal Voltage Low
- Code 23, Throttle Position Sensor MISADJUSTED
- Code 24, Vehicle Speed Sensor Circuit
- Code 31, Manifold Absolute Pressure Sensor Signal Voltage Low
- Code 32, EGR Circuit Loop Error
- Code 33, Map Sensor Signal Voltage High
- Code 51, Prom Problem
- Code 52, ECM Fault
- Code 53, Voltage Reference Overload