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Bosch ML4.1 Injection Self Diagnosis

I had heard that the 16V 33 is capable of self diagnosis of problems by using a small switch and a button to trigger a flash code. Thanks to Primoz on the Alfa 33 discussion list here is a brief description of how to trigger this function, and the meanings of the various different flash codes.

The universal diagnostic connector T2 is for blink code self dignosis. The T2 connector should be connected with the usual switch on the pin 3 (ligh-blue yellow wire) and pin 4 (black) and the lamp (I put the Led dioda and 1k resistance series) should be connectied on pin 2 (pink) and 1 (ligh-blue red). Blink code has four blink blocks for each fault. Each block is coded with 1 to 9 numbers. One blink is coded with number 1 nine blink with number 9. The pause between blocks is longer than between blinks.

Self diagnosis is called as follows:

1. Turn the ignition key into on

2. Press switch for 5 sec.

3. Blink code starts

4. The lamp performs a long flashing (about 2.5 seconds). Following this flashing, series of short flashings is performed (about 0.5 seconds), record the number of flashings since this is the first digit of the blink code (consisting of four digits) which will allow identification of the malfunction. Each series of short flashings is separated by a long flashing.
If the code of the first series of flashings is 4-4-4-4, that means the control unit has stored no errors.

5. Each stored fault requires a new pressing switch for for 3 sec.(the system will repeat the last sequence of flashings, until the switch will be press for 3 sec.)

6. When all malfunctions have been displayed, the lamp performs a series of long flashings

All stored failure in the ECU can be reset in two of the following modes:

- Disconnecting the battery (-) lead for at least 10 seconds.

- After a series of long flashings, a new press longer than 10 sec.

If the lamp goes off during the engine start or immediately after that, ECU has registered no faults.

If the lamp is on with engine running, ECU has registered at last one failure.

Malfunction Code Fault
4-4-4-4 No malfunction displayed-malfunctions memory clear.
1-2-1-1 Abnormal battery voltage (16V).
1-2-1-2 Short circuit to ground of minimum throttle opening switch.
Check conditions:
Engine speed>1000RPM.
Engine temperature>80.2C(176.36F).
Engine load >2.5 msec.
Malfunction duration >5 sec.
1-2-1-3 Short circuft to ground of maximum throttle opening switch.
Check conditions:
Min. Throttle opening switch pressed.
Engine load <3 msec.
1-2-1-4 a.Temperature sensed by engine coolant temperature sensor above 140.3C (284.54F), or short circuit to battery positive pole.
b.Temperature sensed by engine temperature sensor below -35.4C (-95.72F), or circuit interrupted.
Check conditions: Air temperature >-20C (-68F).
1-2-2-1 Airflow meter indications not appropriate to engine RPM and position of idle adjustment switch.
Short circuift to battery positive pole of air flow meter.
Short circuit to ground of air flow meter.
Circuit interrupted.
1-2-2-2 a.Short circuit to ground of the final stage of the idle adjustment actuator, or circuit interrupted.
b.Short circuit to battery positive pole of the final stage of idle adjustment actuator.
1-2-2-3 The heated lambda probe regulator inner adjuster reaches the minimum or the maximum value of correction.
1-2-2-4 a.The heated lambda probe transmits to the control unit a tension 1.009V or <0.0928V.
b.The heated lambda probe malfunction persists for more than 2.5 sec.
After the following conditions verify:
Engine temperature <74.6C (166.28F) for at least 3 minutes.
Engine load > 4 msec for at least 5 seconds.
1-2-2-5 a.Temperature displayed by intake air flow meter above 140.3C (284.54F).
b.Temperature displayed by intake air flow meter below,- 35.4C (95.72F).
Check conditions:
At least 180 seconds after engine start.
Minimum throttle opening switch pressed for at least 30 seconds after 180 seconds from engine start.
1-2-4-3 a.Fuel pump relay final stage short circuited to ground, or circuit interrupted.
b.Fuel pump motronic relay final stage short circulted to battery positive pole.
Check conditions:
The malfunction is identified only if conditions that require pump operation exist (starting phase, or engine running).
The above malfunction can be identified only when another actuator is malfunctioning.
1-2-4-4 a.Evaporation solenoid valve final stage short circuited to ground, or circuit interrupted.
b.Evaporation solenoid valve final stage short circuited to battery positive pole.
Check conditions: The malfunction is identified only during actuationof evaporation solenoid valve (sudden acceleration while standing, or engine under loads).
1-2-5-1 RAM/EPROM memory of control unit is not operating normally.
Replace Motronlc control unit Sll


Output periphery test :

(injection valves, idle regulator and evaporation solenoid valve)

Output perihery is tested by ECU to actuate electromagnets of output periphery. Accurate functioning is indicate by their acoustic (tick-tock) signal.

1. press the switch

2. turn the ignition key into on

3. hold the switch pressed for duration 5 sec.

The codes of the above mentioned procedures are as follows:

Malfunction Code Fault
1-4-1-1 Electro-injectors actuation test activated: continuous control at the frequency of 10 Hz.
4. press switch for 3 sec.
1-4-1-2 Idle adjustment actuator activation test: continuous control for1 second at idle position and I second at maximum speed.
5. press switch for 3 sec.
1-4-1-3 evaporation solenoid valve actuation test: continuous control at the frequency of 0.5 Hz


I haven't verified that this all works (yet), so please use it with care. Note, these flash codes seem to show very little overlap with those used on the MP3.1 system used on late IE model 33's