Reading Trouble Codes
The ECM stores component failure information under a related trouble code which can be recalled for diagnosis and repair. Read trouble codes by counting SERVICE ENGINE SOON light flashes or with diagnostic scan tester connected to the ALDL connector. The tester is faster, and capable of reading information which would require testing individual ECM and sensor/solenoid connector terminals with a digital voltmeter. See SCAN TESTER DATA table and SCAN TESTER USAGE.
If scan tester is not available, SERVICE ENGINE SOON light flashes can be read by grounding ALDL diagnostic terminal with ignition on and engine off. For example, FLASH, FLASH, pause, FLASH, longer pause, indicates Code 21. The first series of flashes are the first digit of trouble code. The second series of flashes are the second digit of trouble code. Trouble codes are displayed starting with the lowest code. Each code is displayed 3 times and will continue as long as ALDL is grounded.
| Code | Probable Cause | ||
|---|---|---|---|
| 12 (1) | No Engine Speed Sensor Reference Pulse To PCM/TCM | ||
| 13 (1) | Open Oxygen Sensor Circuit | ||
| 14 (1) | CTS Voltage Low (Sensor Or Signal Line Grounded) | ||
| 16 (1) | System Voltage High/Low (3.8L) | ||
| 17 (1) | RPM Signal Problem (3.8L) | ||
| 18 (1) | Cam/Crank Error (3.8L) | ||
| 15 (1) | CTS Voltage High (Sensor, Connections, Or Wires Open) | ||
| 21 (1) | TPS Voltage High (Open Circuit Or Misadjusted TPS) | ||
| 22 (1) | TPS Voltage Low (Circuit Grounded) | ||
| 24 (1) | Vehicle Speed Sensor Circuit Open Or Grounded | ||
| 26 (1) | Quad-Driver "B" Fault (3.8L) | ||
| 31 (1) | Park/Neutral Switch Circuit (3.8L) | ||
| 32 (1) | EGR Error (Improper Vacuum Signal) | ||
| 33 (1) | MAP Voltage High (Circuit Open Or Short To Voltage) | ||
| 34 (1) | MAP Voltage Low (Circuit Open Or Short To Ground) | ||
| 34 (1) | MAF Sensor Signal Voltage Low (3.8L) | ||
| 36 (1) | Shift Control Problem (3.8L) | ||
| 38 (1) | Brake Switch Circuit (3.8L) | ||
| 39 | TCC Stuck Off (Faulty TCC Solenoid) | ||
| 41 (1) | Cam Sensor Circuit (3.8L) | ||
| 42 (1) | EST Circuit Fault | ||
| 43 (1) | ESC Fault | ||
| 44 (1) | Lean Exhaust Indicated | ||
| 45 (1) | Rich Exhaust Indicated | ||
| 51 (1) | Improperly Installed/Faulty PROM/MEM-CAL | ||
| 52 (1) | Fuel CAL-PAC Missing | ||
| 54 (1) | Fuel Pump Circuit Voltage Low | ||
| 55 (1) | Faulty ECM | ||
| 56 (1) | Quad-Driver "B" Fault (3.8L) | ||
| 61 (1) | Cruise Vent Solenoid (3.8L) | ||
| 62 (1) | Cruise Vacuum Solenoid (3.8L) | ||
| 63 (1) | Cruise System Problem (3.8L) | ||
| 65 (1) | Cruise Servo Position (3.8L) | ||
| 66 (1) | Low A/C Refrigerant Charge (3.8L) | ||
| 67 (1) | Cruise Engage Switches (3.8L) | ||
| 68 (1) | Cruise System Problem (3.8L) | ||
| 69 (1) | A/C Head Pressure Switch (3.8L) | ||
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