If the ECU detects a problem, the orange “Check Engine” light comes on. This in itself isn’t very helpful. However, it’s pretty simple to get the orange “Check Engine” light to provide a little more information as to what might be wrong. Refer to Reading Engine Codes for instructions on how to get the codes from the car, and also for instructions on how to clear the code.
For the UK error codes refer to IMOC.
1985-1987 4AGE
Uses single digit codes: 1-Normal, 2-Air flow meter, 3-Ignition signal, 4-Water temperature sensor, 5-Oxygen sensor signal, 6-RPM signal, 7-Throttle position sensor, 8-Intake temperature sensor signal, 10-Starter signal, 11-Switch signal
1988-1989 4AGE
Uses two digit codes: 12-RPM signal, 13-RPM signal, 14-Ignition signal, 21-Oxygen sensor signal/oxygen sensor heater, 22-Water temperature sensor signal, 24-Intake air temperature sensor signal, 25-Air-fuel ratio lean malfunction, 26-Air-fuel ratio rich malfunction, 31-Air flow meter signal, 41-Throttle position sensor signal, 42-Vehicle speed sensor signal, 43-Starter signal, 51-Switch signal, 71-EGR system malfunction
1988-1989 4AGZE
Uses two digit codes: 11-ECU (+B), 12-RPM signal, 13-RPM signal, 14-Ignition signal, 21-Oxygen sensor signal/oxygen sensor heater, 22-Water temperature sensor signal, 24-Intake air temperature sensor signal, 25-Air-fuel ratio lean malfunction, 26-Air-fuel ratio rich malfunction, 31-Air flow meter signal, 32-Air flow meter signal, 41-Throttle position sensor signal, 42-Vehicle speed sensor signal, 43-Starter signal, 51-Switch signal, 52-Knock sensor signal, 53-Knock control signal in ECU, 71-EGR system malfunction
Many of the codes indicate a fault with the ECU. Whilst the ECU does fail it is rare, and other options should be fully explored first.
| 1-Digit | 2-Digit | Meaning |
|---|---|---|
| 1 | None | Normal – no problem |
| 11 | Loss of power to ECU: ignition switch/circuit; main relay/circuit; ECU | |
| 6 | 12 | RPM signal/no-signal to ecu from distributor (“ne” or “g”) after engine has been cranked: distributor/circuit; starter/signal circuit; igniter/igniter circuit; ECU |
| 13 | Same as 12 but after engine has run at 1,000-1,500 rpm: distributor/distributor circuit; ECU | |
| 3 | 14 | Ignition signal (no “igf” signal to ecu, no signal from igniter 4 times in a row): igniter/igniter circuit; igniter and ignition coil/circuit; ECU |
| 5 | 21 | Oxygen Sensor signal/oxygen sensor heater signal: open/short in oxygen sensor or signal |
| 4 | 22 | Water temperature sensor signal (open or short in water temperature sensor signal): water temperature sensor circuit; water temperature sensor; fault in coolant temperature sensor circuit; ECU |
| 8 | 24 | Intake air temperature sensor signal: open or short in intake air temperature signal; intake air temperature circuit; intake air temperature sensor; ECU |
| 25 | Air/fuel ratio lean indicator (lean signal sent to ECU from oxygen sensor): injector fault(s); injector circuit; injector; oxygen sensor circuit; oxygen sensor; air leak; fuel pressure line; airflow meter or map sensor; ECU. Try cleaning the injectors. | |
| 26 | Air/fuel ratio rich indicator: same as 25; cold start injector | |
| 27 | Sub-oxygen sensor circuit or sub-oxygen sensor heater circuit; ECU | |
| 28 | #2 oxygen sensor/oxygen sensor heater; same as code 21 | |
| 2 | 31 | Manifold and/or airflow meter sensor signal circuit: airflow meter/circuit; manifold pressure sensor/circuit; ECU |
| 32 | Airflow meter signal (vane-type): airflow meter/circuit; ECU | |
| 14 | 34 | Abnormal turbocharger pressure: turbo charger; airflow meter/manifold/turbocharger pressure sensor; intercooler system; ECU |
| 35 | Turbocharger pressure sensor signal: turbocharger pressure sensor; ECU | |
| 7 | 41 | Throttle position sensor signal: open or short in tps signal; tps sensor; tps signal/circuit; ECU |
| 9 | 42 | Vehicle speed sensor signal circuit (no speed signal for several seconds): while vehicle is operated under heavy load (tps/map/air flow inputs); speed sensor/circuit; ECU |
| 10 | 43 | Starter signal (no “sta” signal to ecu until engine speed exceeds 800rpm): vehicle is push started; ignition switch/circuit; ECU. Not a real problem unless it recurs. |
| 11 | 51 | Switch signals: TPS idle switch off; neutral start switch off (automatic transmission in Drive); A/C switch on; A/C switch/circuit; A/C amplifier; TPS/circuit; neutral start switch/circuit; ECU |
| 12 | 52 | Knock sensor signal (open or short in knock sensor signal): knock sensor/circuit; ECU |
| 13 | 53 | Knock control signal in ECU |
| 71 | EGR valve malfunction (exhaust gas tempeature below specification for EGR control): EGR system; EGR gas temperature sensor/circuit | |
| 72 | Air conditioner compressor relay/relay signal: A/C compressor relay/circuit; ECU |