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A3 1.6 Engine cutting out when hot then difficut to start (ASR light on) SOLVED!!!

johnone Apr 12, 2010

  1. johnone

    johnone 5th Gear

    Hi all, Thought I would post some info on a recent problem with my 2002 1.6 A3 (BFQ)

    The car would be fine starting from cold get up to temperature, then would cut out, usually when slowing down.
    Trying to start the car again would take 5+ cranks of the engine before it would splutter into life.
    The Traction control (ASR) and engine management light came on and eventually put the car into limp home mode.

    Leaving the car to cool down (2 hours ish) it would then start up ok without issue.
    However again, after getting up to temperature and slowing down to do a right turn, it konked out again.
    When I got it back home, I checked the ECU for error codes:

    17925 - Main Relay (J271) Electrical Malfinction
    P1517 - 35-10 - - - Intermittent

    16514 - Oxygen (Lambda) Sensor B1 S1: Malfunction in Circuit
    P0130 - 35-10 - - - Intermittent

    16706 - Engine Speed Sensor (G28): No Signal
    P0322 - 35-00 - -

    To fully qualify the error I cleared the ECU DTC's and test drove the car.
    Again the problem occured when the engine had got up to temperature and been driving for about 30 mins.

    Each time the ASR (Traction control) would light up on the dash and stay on, reducing power considerably.

    Several clears of the ECU codes and test drives flagged up:
    16706 - Engine Speed Sensor (G28): No Signal
    P0322 - 35-00 - -

    Having read a few posts on the net I read that a faulty Crankshaft position sensor causes the issues I have been experiencing. I figure that the sensor breaks down under thermal stress. That is as the sensor gets hot it fails.
    The sensor is a hall effect sensor: http://en.wikipedia.org/wiki/Hall_effect_sensor

    I decided the problem could be one of 3 possible things:
    1. Fuel Pump Relay
    2. Camshaft Position Sensor
    3. Crankshaft Position Sensor
    I replaced the fuel pump relay (£22) to no avail.

    Having purchased the camshaft sensor and looked at the job to remove it, I deciede not to - located under the throttle body!!

    So finally, we replaced the engine speed sensor (crankshaft position sensor) £82 from Audi or £50 from eurocarparts.com (494 44 0420).

    The crankshaft position sensor is located to the right of the oil filter on the engine block.
    The easiest way to change it is to remove the hoses from the oil cooler to gain access.
    Then a 5mm HEX bolt needs to be removed to free the sensor.

    This webpage has some good photos of the sensor on an Audi A2 - however the bolt is different on this:

    (search for audi a2 crankshaft position sensor with a search engine)

    Having researched the problem it would appear theat the crankshaft position sensor is vital for a number of reasons:
    • Provides info to the traction control system on how fast the engine is revolving - hence the reason why the ASR light came on and why the traction control was fighting the engine for power.
    • Provides info to the ECU for injection timing, fuel delivery and so I have read if this signal is not present the ECU stops the fuel pump as a saftey feature.
    I am happy to say that after replacing the Crankshaft Position Sensor (engine speed sensor) all is well!
    And the engine actually ticks over smoother! :cool:

    Hope that info may help others who experience similar issues! [​IMG]
  2. martin g

    martin g [censored]

    Thats usefull to know John thanks :icon_thumright:

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