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Engine rpm signal to the MIU, TCS and AF22control modules

Symptom: Diagnostic trouble codes generated in the MIU, TCS and/or AF22 systems

Engine rpm signal to the MIU, TCS and AF22 control modules


Fault symptom

Diagnostic trouble codes generated in the MIU, TCS and/or AF22 systems



Diagnostic procedure


1. Start the engine and use the ISAT command "ENGINE RPM SIGNAL" in the "READ ON/OFF" menu. If the control module sends out engine rpm signals, the ISAT display should read "ACTIVE".

If the ISAT shows "INACTIVE", turn to for further diagnostic instructions.

2. If the ISAT display reads "ACTIVE", clear all diagnostic trouble codes in the MIU, TCS and/or AF22 systems and drive the car to see whether any are generated afresh. If they are, continue as described below.



With the ignition switched off, connect a BOB to the MOTRONIC control module and cable. Check that there is a signal of about 6.5 V and 40 Hz on pin 43 at idling speed. At 2500 rpm the signal should be about 6.5 V and 125 hz.

If the signal is OK, the fault lies either in the leads connected to the MIU, TCS and/or AF22 control modules or in any of these systems.

If there is no output signal on pin 43, it may be on account of a short circuit to ground/batt+ in any of the leads connected to the above systems. Rectify any faults.

If there is no short circuit, turn to for further diagnostic instructions.