Malfunction indicator
Malfunction indicator (MIL — Malfunction Indicator Lamp) lights up when the ignition is turned on to check the lamp. After starting the engine, it should go out.
If, after switching on the ignition, the signaling device does not light up, it is necessary first of all to check the lamp and the contacts in the signaling device circuit.
Switching diagnostic modes
Diagnostic mode I: set immediately after the ignition is switched on (fault warning lamp test). After starting the engine, the warning device will issue a warning about detected malfunctions.
Diagnostic mode II: when the engine is not running and the ignition is on, the indicator displays the results of self-diagnosis. After starting the engine in this mode, continuous monitoring of the oxygen sensor is carried out.
Mode switching is possible only when the engine is not running and the ignition is on. To do this, turn the mode selector on the engine control unit clockwise to the stop, wait at least 2 seconds and turn the selector back. Another way to switch is to close the SNK and IGN contacts of the diagnostic connector with a suitable conductor for at least 2 seconds. (for the SR engine, only this method is applicable).
If the ignition is turned OFF in diagnostic mode II, power will be removed from the ECM after approximately 5 seconds. in GA engines and after 1 sec. in the SR engine. After the ignition is switched on, mode I will be automatically set.
During normal operation of the vehicle, the mode selector should be turned counterclockwise as far as it will go.
Diagnostic Mode I - Fault Warning
If the malfunction indicator light comes on in mode 1 with the engine running, this indicates a malfunction in the coolant temperature sensor circuit, or the engine is overheating, or the control unit microprocessor is not working properly.
Diagnostic mode II - output of self-diagnosis results
In this mode, fault codes are issued, for which the fault indicator flashes. Long flashes (0.6 s) indicate tens, short (0.3 s) - units (see fig.).
The issuance of code 55 indicates that there are no malfunctions.
Erasing fault codes
The fault codes generated as a result of self-diagnosis are erased from the backup memory of the control unit when switching from mode II to mode I.
When the battery is disconnected, the codes are stored in the memory for about 24 hours.
Diagnostic Mode II - Oxygen Sensor Monitoring
In this mode, the malfunction indicator indicates the composition of the combustible mixture (enriched or depleted). The indicator is on - lean mixture, off - rich mixture. Monitoring of the oxygen sensor is only possible with a closed feedback loop. The feedback loop opens when starting, warming up and running the engine at normal idle. In this case, the malfunction indicator will be permanently on or off. Check the oxygen sensor as follows:
- Start the engine in diagnostic mode II and warm it up until the pointer of the coolant temperature gauge reaches the middle of the scale.
- Maintain rpm 2000 min-1 for 2 minutes without load, then, without reducing the speed, check the frequency of flashing of the malfunction indicator. It must be at least 0.5 Hz (more than 5 times in 10 s).
Engine operation in emergency mode
The engine goes into emergency operation in the following situations:
- Faulty mass air flow sensor circuit. Engine speed will be limited to 3000 min-1 for GA engines and 2400 min-1 for SR engine.
- Faulty coolant temperature sensor circuit (code number 13). Engine temperatures will be determined by the time elapsed from the start: 35°C immediately after the ignition or starter is turned on, 80°C after 4.5 minutes. The cooling fan will be on all the time.
- Faulty throttle position sensor circuit. The damper position will be determined by the amount of fuel injected and the engine speed. Acceleration dynamics will be bad.
- Faulty start signal circuit (SR engine). If the ECM constantly receives a start signal, then upon reaching 1000 min-1 it is assumed that this signal is absent, which prevents over-enrichment of the combustible mixture.
- Incorrect operation of the processor or other elements of the control unit. In this case, the engine speed is limited to 3000 min-1, injection is carried out simultaneously by all injectors twice during the operating cycle, the ignition timing is set to a constant angle, the fan and the fuel pump are constantly on while the engine is running, the IACV-AAC valve is fully open.