Failure Code Determination

During any diagnostic procedure, "hard failure" codes MUST be distinguished from "intermittent failure" codes. Diagnostic charts CANNOT be used to analyze "intermittent failure" codes, except as noted under Diagnostic Procedure. To determine "hard failure" codes and "intermittent failure" codes, proceed as follows:

1. Turn ignition on and enter diagnostics. Read and record all stored trouble codes. Exit diagnostics and clear trouble codes.
   ECM TROUBLE CODE IDENTIFICATION
   
   

   Code	Circuit Affected	Application
   12	No reference pulse to ECM. (Not stored in memory).	All Models
   13	Oxygen sensor circuit.	Exc. Fed. "T" Car
   14	Shorted coolant temperature sensor circuit.	Exc. Fed. "T" Car
   15	Open coolant temperature sensor circuit.	All Models
   21	TPS circuit high.	All Models
   22	TPS circuit low.	EFI Models Only
   23	Open or grounded M/C solenoid circuit.	Exc. EFI Models
   24	VSS circuit.	Exc. Fed. "T" Car
   32	BARO sensor circuit low. (Altitude compensator low on "J" cars).	Exc. EFI & Fed. "T" Car
   33	MAP sensor circuit high.	EFI Models Only
   34	MAP or vacuum circuit.	Exc. Fed. "T" Car
   35	ISC circuit sorted.	Exc. EFI & Fed. "T" Car
   41	No distributor reference pulses with 8 in. Hg at MAP sensor.	Exc. EFI & Fed. "T" Car
   42	EST circuit or by-pass grounded or open.	Exc. Fed. "T" Car
   43	ESC retard signal too long.	Exc. Fed. "T" Car
   44	Lean oxygen sensor value.	All Models
   44	& 55 At same time, faulty oxygen sensor circuit.	Exc. EFI & Fed. "T" Car
   45	Rich oxygen sensor value.	All Models
   51	Faulty PROM or improper PROM installation.	All Models
   54	Shorted M/C solenoid or faulty ECM.	Exc. EFI & Fed. "T" Car
   55	Grounded voltage regerence, faulty oxygen sensor or ECM.	Exc. Fed. "T" Car

   NOTE: Trouble codes will be recorded on Federal "T" cars only with engine running. Turning ignition off after any trouble codes have been set will erase all codes.
2. Apply parking brake and place transmission in neutral (manual) or park (automatic). Block drive wheels. Start engine. "CHECK ENGINE" lamp should go out. Run warm engine at specified curb idle for 2 minutes and note "CHECK ENGINE" light.
   NOTE: Grounding "TEST" terminal with engine running will force engine to operate in closed loop mode if engine is warm and oxygen sensor is hot. If "CHECK ENGINE" lamp does not glow while in closed loop, CCC system is operating properly.
3. If "CHECK ENGINE" lamp comes on, enter diagnostics, read and record trouble codes. This will reveal "hard failure" codes. Codes "13", "15", "24", "35", "44", "45" and "55" may require road test to reset "hard failure" after trouble codes were cleared.
4. If "CHECK ENGINE" lamp does not come on, all stored trouble codes were "intermittent failures", except as noted under Diagnostic Procedure.
   NOTE: Trouble code "15" malfunction will only display after 5 minutes of engine operation. Trouble code "12" will display only during time of no reference pulses received by ECM; it will never be stored as a malfunction.