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Ma' Beloved AUDI A4 - Engine Management Light not working

issuesaudi Aug 8, 2018

  1. issuesaudi

    issuesaudi New Member


    I have a beloved AUDI A4 TDI 1.9 (B6 96KW 2001)

    The dashboard Check Engine/MIL/ECU light is not turning on when it should be.

    They have made this light a requirement for UK MOT tests this year (oh gawd).

    Main Issue:
    • No ECU light on and off when ignition
    • No ECU light when engine sensors are deliberately tampered with (MAF)

    Had a diagnostic recently done:
    • Car engine is running fine
    • ECU communicates with diagnostic tool
    • ECU logs any fault codes correctly (e.g. MAF tampering)
    • I thus assume the ECU work okay (engine running fine)
    • Cluster ECU Check engine light was tested OK via diagnostic tool
    • I assume the cluster is okay as the bulb can be switched on and off

    How would I start to get someone to diagnose this and fix the issue?

    I understand the immobiliser network has three elements - the ignition, ECU and dash cluster? If each of the elements in this group is working individually, should I conclude there something broken between the ECU to dash cluster which is preventing the light from turning on and off for ignition (or when the engine sensors are deliberately messed with)??

    Could it be a wire, a seating, a pin connector? How can I diagnose this issue and where would be the right area of focus?

    Welcome any advice or questions.
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  3. DieselJake

    DieselJake Well-Known Member VCDS Map User

    Very strange! Sounds like a wire/connection issue as you say, if your anywhere near Birmingham or coming to AITP bring it to us and I'll get it on vag com which will probably bring back a bit more than what the garage got.

    Probably not related but I had/fixed some electrical faults on mine due to water getting in the electrics https://www.audi-sport.net/xf/threads/1-9tdi-not-starting.374890/
  4. issuesaudi

    issuesaudi New Member

    Hi, where abouts you in Brum?

    Got the garage to pull some sensors out of engine to see if check-engine light would come on - ECU light did not come on. When checked with VAGCOM the ECU did record the deliberate issues - so ECU is working fine as engine is OK as well - just is not communicating with the dash cluster to switch on light on self-check startup with ignition or if there is engine fault.

    The glow plug does come on dash with self-check ignition which (I understand) is controlled by ECU - so the comms between ECU and cluster must be working to some extent.

    I guess cheapest option is to change cluster (can get a 2nd hand one of ebay) but will require immobilizer mapping when dash is replaced. You know how this can be done and cost of it?

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