OBD Codes

On Board Diagnostic Codes

Checking on board diagnostics can be tricky, but here are a list of simple codes and their meanings:

1985 TO 1991: 

Code #12: Normal No Codes. 
Code #13: Open Oxygen Sensor Circuit. 
Code #14: Coolant Sensor Circuit Low. 
Code #15: Coolant Sensor Circuit High. 
Code #21: Throttle Position Sensor High. 
Code #22: Throttle Position Sensor Low. 
Code #23: Manifold Air Temperature Circuit High. 
Code #24: Vehicle Speed Sensor. 
Code #25: Manifold Air Temperature Circuit Low. 
Code #32: EGR System Failure. 
Code #33: Mass Air Flow Sensor High. 
Code #34: Mass Air Flow Sensor Low. 
Code #36: Mas Air Flow Sensor Burn-Off Function Fault. 
Code #41: Cylinder Select Error. 
Code #42: Electronic Spark Timing. 
Code #43: Electronic Spark Control. 
Code #44: Lean Exhaust indication. 
Code #45: Rich Exhaust Indication. 
Code #46: Vehicle Anti Theft Fault. 
Code #51: Faulty Mem-Cal. 
Code #52: Fuel Calpak Missing. 
Code #52(1990-91 Corvette Only): Engine Oil Temperature Sensor Low. 
Code #53: System Over Voltage. 
Code #54: Fuel Pump Circuit Low Voltage. 
Code #55: Defective ECM. 
Code #62: Engine Oil Temperature Sensor Circuit High.

ECM CODES 1992 TO 1993: 

Code #12: Normal No Codes. 
Code #13: Left Oxygen Sensor Circuit. 
Code #14: Coolant Temperature Sensor Circuit High. 
Code #15: Coolant Temperature Sensor Circuit Low. 
Code #16: Opti-Spark Ignition Timing System.( Low Pulse) 
Code #21: Throttle Position Sensor Circuit High. 
Code #22: Throttle Position Sensor Circuit Low. 
Code #23: Intake Air Temperature Sensor Circuit Low. 
Code #24: Vehicle Speed Sensor Circuit. 
Code #25: Intake Temperature Sensor Circuit High. 
Code #26: Quad-Driver Module #1 Circuit. 
Code #27: Quad-Driver Module #2 Circuit. 
Code #28: Quad-Driver Module #3 Circuit. 
Code #32: Exhaust Gas Recirclation Circuit. 
Code #33: Manifold Absolute Pressure Sensor Circuit Low. 
Code #34: Manifold Absolute Pressure Sensor Circuit High. 
Code #36: Opti-Spark Ignition Timing System. (High Resolution Pulse.) 
Code #41: Electronic Spark Timing Circuit Open
Code #42: Electronic Spark Timing Circuit Grounded. 
Code# 43: Electronic Spark Control Circuit. 
Code #44: Left Oxygen Sensor Circuit Lean. 
Code #45: Left Oxygen Sensor Circuit Rich. 
Code #51: Mem-Cal Error. 
Code #52: Engine Oil Temperature Sensor Circuit Low. 
Code #53: System Voltage. 
Code #55: Fuel Lean Monitor. 
Code #56: Vacuum Sensor Circuit. 
Code #61: Secondary Port Throttle Valve System. 
Code #62: Engine Oil Temperature Sensor Circuit High. 
Code #63: Right Oxygen Sensor Circuit Open. 
Code #64: Right Oxygen Sensor Circuit Lean. 
Code #65: Right Oxygen Sensor Circuit Rich. 
Code #66: A/C Pressure Sensor Circuit Open. 
Code #67: A/C Pressure Sensor Circuit. (Sensor or A/C Clutch Circuit Problem) 
Code #68: A/C Relay Circuit Shorted. 
Code #69: A/C Clutch Circuit. 
Code #72: Gear Selector Switch Circuit.




CODES 1994 TO 1996: 

DTC #11: Malfunction Indicator Lamp Circuit. 
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit: 
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low. 
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High. 
DTC #16: Distributor Ignition System Low Pulse. 
DTC #18: Injector Circuit. 
DTC #21: Throttle Position Sensor Circuit Voltage High. 
DTC #22: Throttle Position Sensor Circuit Voltage Low. 
DTC #23: Intake Temperature Sensor Circuit Voltage High. 
DTC #24: Vehicle Speed Sensor Circuit. 
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low. 
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit. 
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit. 
DTC #28: Transmission Range Pressure Switch Assembly Fault. 
DTC #29: Secondary Air Injection Pump Circuit. 
DTC #32: Exhaust Gas Recalculation. 
DTC #33: Manifold Absolute Pressure Sensor Circuit High. 
DTC #34: Manifold Absolute Pressure Sensor Circuit Low. 
DTC #36: Distributor Ignition System High Pulse. 
DTC #37: Brake Switch Stuck On. 
DTC #38: Brake Switch Stuck Off. 
DTC #41: Ignition Control Circuit Open. 
DTC #42: Ignition Control Circuit Shorted. 
DTC #43: Knock Sensor Circuit. 
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean. 
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich. 
DTC #47: Knock Sensor Circuit Or Module Missing. 
DTC #48: Mass Air Flow Sensor Circuit. 
DTC #50: System Voltage Low. 
DTC #51: EEPROM Programming Error. 
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low. 
DTC #53: System Voltage Low. 
DTC #55: Fuel Lean Monitor. 
DTC #58: Transmission Fluid Temperature Sensor Circuit Low. 
DTC #59: Transmission Fluid Temperature Sensor Circuit High. 
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low. 
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open. 
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean. 
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich. 
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch. 
DTC #68: A/C Relay Circuit. 
DTC #69: A /C Clutch Circuit. 
DTC #70: A/C Clutch Relay Driver Circuit. 
DTC #72: Vehicle Speed Sensor Loss. 
DTC #73: Pressure Control Solenoid Circuit Current Error. 
DTC #74: Traction Control System Circuit Low. 
DTC #75: Transmission System Voltage Low 
DTC #77: Primary Cooling Fan Relay Control Circuit. 
DTC #78: Secondary Cooling Fan Relay Control Circuit. 
DTC #79: Transmission Fluid Overtemp. 
DTC #80: Transmission Component Slipping. 
DTC #81: Transmission 2-3 Shift Solenoid Circuit. 
DTC #82: Transmission 1-2 Shift Solenoid Circuit. 
DTC #83: Torque Converter Solenoid Voltage High. 
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only). 
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit. 
DTC #85: Transmission TCC Stock On. 
DTC #90: Transmission TCC Solenoid Circuit. 
DTC #91: One To Four Upshift Lamp(Manual Only). 
DTC #97: VSS Output Circuit. 
DTC #98: Tachometer Output Signal Voltage Wrong.