Trouble Code Definitions

CODE IDENTIFICATION

Code No.

System Affected

Probable Cause

12 ⁽¹⁾

Ignition Ref. Signal

Dist. Or Circuit, ECM

13 ⁽²⁾

Open O2 Sensor

Sensor/Circuit ECM

14 ⁽³⁾

Shorted Coolant Temp. Sensor Signal

Sensor/Circuit, ECM

15 ⁽⁴⁾

Open Coolant Temp. Sensor Signal

Sensor/Circuit, ECM

21 ⁽⁵⁾

Idle (Vacuum) Switch & MAP Sensor

Sensor/Circuit, ECM

22 ⁽⁶⁾

Fuel-Cut Solenoid Circuit

Solenoid/Circuit, ECM

23 & 54

Duty (Mixture Control) Solenoid Circuit

Solenoid/Circuit, ECM

25 & 53

AIR Management Valve Circuit

VSV/Valve Circuit, ECM

26 & 27

Canister Purge VSV Circuit

VSV/Valve Circuit, ECM

31 ⁽²⁾⁽⁷⁾

Ignition Ref. Signal

Wiring Circuit, ECM

EGR System

EGR Valve, Thermal Vac. Valve or Backpressure Transducer

EGR Gas Temp. Sensor

Sensor/Circuit, ECM

VSV: MAP Sensor Failure

Constant High Voltage From VSV to ECM

VSV: MAP Sensor Failure

MAP Sensor VSV Circuit

44 ⁽²⁾⁽⁸⁾

O2 Sensor (Lean)

Mixture Control Solenoid, O2 Sensor, ECM

45 ⁽²⁾⁽⁹⁾

O2 Sensor (Rich)

Mixture Control Solenoid, O2 Sensor, ECM

Fuel-Cut Solenoid

See Code 22

Faulty ECM RAM

ECM

AIR Management Valve

See Code 25

Mixture Control Solenoid

See Code 23

Faulty ECM

ECM

⁽¹⁾	Code 12 is a normal response to key on and engine off with ALDL test lead installed.

⁽²⁾	Requires engine operation at part throttle under load for up to 5 minutes after engine reaches normal operating temperature to set code.

⁽³⁾	Engine must be running at least 2 minutes before code will be set.

⁽⁴⁾	Engine must be running at least 5 minutes before code will be set.

⁽⁵⁾

Code will set if one of following conditions exist: Engine speed is 200-1000 RPM and vacuum applied to MAP sensor is more than 20 in. Hg for 5 seconds or, idle switch is off and vacuum applied to MAP sensor is less than 4 in. Hg for 5 seconds or, engine speed is greater than 1500 RPM, vacuum applied to MAP sensor is 16-18 in. Hg and idle switch is on for 5 seconds.

⁽⁶⁾	Engine must be decelerating and engine speed greater than 2000 RPM before code will be set.

⁽⁷⁾	No reference signal to ECM after 10 seconds at part throttle under load. Code will be stored in memory.

⁽⁸⁾	Engine speed must be less than 2500 RPM and exist for 5 seconds after fuel-cut recovery. Code will set except when vacuum reading to MAP sensor is less than 23 in. Hg, Code 13 or 21 is stored, or coolant temperature is greater than 302°F (150°C).

⁽⁹⁾

Engine speed must be less than 2500 RPM with vehicle speed of 12-50 MPH for more than 30 seconds after canister purge. Code will set except when vacuum reading to MAP sensor is less than 23 in. Hg, Code 13 or 21 is stored, coolant temperature is greater than 302°F (150°C) or under high altitude conditions greater than 8000 ft. (2434 meters).