Motronic Self-Diagnosis

From: FredAlfa@aol.com
Date: Mon, 2 Dec 1996 15:29:28 -0500
This procedure applies to '91-'93 164s

SELF-DIAGNOSIS - GENERAL INFORMATION

The diagnosis procedure is divided in two groups:
A = Display of errors stored by the control unit.
B = Monitoring of some engine actuators and devices.

The button provided on the steering column performs three separate functions, depending on duration of pressure on the button; these functions are as follows:
T1 = Pressure duration between 2.5 and 5 seconds.
T2- Pressure duration between 5 and l0 seconds.
T3. Pressure duration over l0 seconds.

To select procedure A press the pushbutton for duration Tl after the ignition key has been turned to 'run" position.

To select procedure B press the pushbutton first, then rotate the ignition key to position1 and hold the pushbutton pressed for duration Tl.

Procedure A

Press pushbutton for duration Tl after the ignition key has been turned to "run" position: the CHECK ENGINE warning 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 error code (consisting of four digits) which will allow identification of the malfunction. Each series of short flashings is separated by a long flashing.

By pressing again the pushbutton for a period Tl will display the second digit of the error code, and so on until all the five defects that can be stored in the control unit memory are displayed. If the pushbutton is not pressed, the systemwill repeat the last sequence of flashings, thus allowing to check the recorded code.

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

If the code of the first series of flashings is 4-4-4-4, that means the control unit has stored no errors.

Pressing the pushbutton for duration T2, the warning lamp will repeat the flashings from the beginning.

The control unit memory can be reset in any of the following modes:

In any case, if the malfunction is no longer present, the control unit is automatically reset after 50 engine starts.

Procedure B

Press and hold the pushbutton and turn the ignition key to 'run" position. Subsequently, hold pushbutton pressed for duration Ti after the ignition key has been turned, but with engine not running.

A few seconds after the pushbutton has been released, the electro-injectors will begin to operate, while the CHECK ENGINE warning lamp will indicate which actuator has been activated by means of a four digits code in accordance with methodology described for procedure A.

The sequence of activated actuators is as follows:

  1. Electro-injectors.
  2. Idle adjustment actuator.
  3. Evaporation solenoid valve.

Pressing the pushbutton for duration T2 you will return to the beginning of procedure with actuation of the electro-injectors.

Pressing the pushbutton for duration T3 the activation of actuators is completed. The codes of the above mentioned procedures are as follows:

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

If operator performing the check has a device which is capable to interface with the control unit on a 'SIX pole" line, two other codes can be obtained, as follows:

1-2-6-5
short circuit towards ground of final stage of CHECK ENGINE error warning lamp. Short circuit towards battery positive of final stage of CHECK ENGINE error warning lamp.
1-5-5-5
inability of the control unk to receive control inputs and to emit control outputs to the CHECK ENGINE warning lamp.

The following table contains the troubleshooting for the Motronic ML4.1 system where, starting from the flashing error code displayed by,the CHECK ENGINE warning lamp, the existing failure can be detected, and the faulty components can be identified.


SELF-DIAGNOSIS - TROUBLESHOOTING TABLE

CODE
MALFUNCTION
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:
1-2-1-3
Short circuft to ground of maximum throttle opening switch.
Check conditions:
1-2-1-4
  1. Temperature sensed by engine coolant temperature sensor above 140.3-C (284..54-F), or short circuit to battery positive pole.
  2. Temperature sensed by engine temperature sensor below -35.4"C (-95.720F), or circuit interrupted.
Check conditions: Air temperature >-20oC (-68oF).
1-2-2-1
Airflow meter indications not appropriate to engine RPM and position of idle adjustment switch.
1-2-2-2
  1. Short circuit to ground of the final stage of the idle adjustment actuator, or circuit interrupted.
  2. 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
  1. The heated lambda probe transmits to the control unit a tension 1.009V or <0.0928V.
  2. The heated lambda probe malfunction persists for more than 2.5 sec.
After the following conditions verify:
1-2-2-5
  1. Temperature displayed by intake air flow meter above 140.3oC (284.54-F).
  2. Temperature displayed by intake air flow meter below,- 35.4oC (95.72oF).
Check conditions:
1-2-4-3
  1. Fuel pump relay final stage short circuited to ground, or circuit interrupted.
  2. Fuel pump motronic relay final stage short circulted to battery positive pole.
Check conditions: The above malfunction can be identified only when another actuator is malfunctioning.
1-2-4-4
  1. Evaporation solenoid valve final stage short circuited to ground, or circuit interrupted. K
  2. Evaporation solenoid valve final stage short circuited to battery positive pole.
Check conditions:
1-2-5-1
RAM/EPROM memory of control unit is not operating normally. Replace Motronlc control unit Sll
None
  1. CHECK ENGINE warning lamp inoperative.
  2. CHECK ENGINE warning lamp continuously illuminated.

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