No Communication

Chat about your MKV (6N2) Polo
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S1ev3
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Posts: 1
Joined: Sun Oct 10, 2021 12:09 pm
Drives: 2000 6N2 1.4 AUD
Location: Germany

No Communication

Post by S1ev3 »

Hi
I'm English but working in Germany, I have a left hand drive 2000 Polo 1.4 AUD engine. As part of the German equivalent to the MOT the codes are read. One of the reasons the car failed the inspection was "Motormanagement- / Abgasreinigungsystem (Otto) nicht Ordnung." Which translates to "Engine management / emission control system (Otto) not working properly." However there is no engine light on.
Basically nothing will connect to it, No communication. I have use of a Snap On Modis which works fine on other vehicles but wont communicate with any systems on this Polo. I have read on Ross-tech about a high voltage on the K-Line causing a no comms situation, often caused by an aftermarket head unit. With the ignition on I have 12V on the K-Line, The car does have an aftermarket head unit which I have checked and the K-Line is not connected. I removed the head unit anyway and there's no change.
With the ignition off there is 4.5V on the K-Line and as soon as the ignition is switched on it rises to battery voltage. Ross-tech suggests it needs to be below 9V for scan tools to work.
I have tried a couple of scenarios to try and find the source of the 12V.
With the instrument cluster unplugged there is no difference, engine starts ok.
With the ABS module unplugged there is no difference, engine starts ok.
With the engine ECU there is no difference to the voltage, engine cranks but no start as expected but the voltage remains.
I've checked all the fuses which all seem good but I noticed upon removing the immobiliser fuse the voltage does drop but is still over 9V, Engine still starts but shuts off after a second which is to be expected.
Does anyone know what other modules use the K-Line and where they are located to try and eliminate the source of this high voltage and then hopefully get communication back.
Thanks
Steve.
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