P0688 - crank no start
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P0688 - crank no start
2004 Audi TT 1.8l BEA
Drove vehicle fine. Went to drive next day and wouldn't start. P0688, p1602, p1603. Battery had gotten low and was charged, and may be the cause of the 1602/1603 codes.
P0688 - ecm isnt seeing voltage for the relay circuit.
- what fuse should I be referring to on my driver side dash panel for this? There are 3-4 regarding ignition timing. #29 pops up with this code for every post I've seen. It's good and has battery voltage. There is another fuse 37 or 42? That is labeled for ignition timing "petrol" TT/VR6. I believe that one is getting .3 or .9V can't remember which but not battery voltage.
So any who, relay 100 and 428 have been replaced to verify. Seems relay 100 is for the coils, violet wire from that relay goes straight to the ECM. Getting battery voltage at the relay and at ECM connector with key off. Key on drops to .9v. Cut the wire and getting battery voltage at either end of the wire, even overlayed it. Only when connected to the ECM does it drop to .9v.
Checked harness about 6-8" from ECM for issues. Only issue noted was the big red and smaller red/green wire that splices to tiny red/green wire. Battery voltage at splice, drove 1.5v+ back probing at ECM.
Thoughts? Short to ground? Things to check?
Drove vehicle fine. Went to drive next day and wouldn't start. P0688, p1602, p1603. Battery had gotten low and was charged, and may be the cause of the 1602/1603 codes.
P0688 - ecm isnt seeing voltage for the relay circuit.
- what fuse should I be referring to on my driver side dash panel for this? There are 3-4 regarding ignition timing. #29 pops up with this code for every post I've seen. It's good and has battery voltage. There is another fuse 37 or 42? That is labeled for ignition timing "petrol" TT/VR6. I believe that one is getting .3 or .9V can't remember which but not battery voltage.
So any who, relay 100 and 428 have been replaced to verify. Seems relay 100 is for the coils, violet wire from that relay goes straight to the ECM. Getting battery voltage at the relay and at ECM connector with key off. Key on drops to .9v. Cut the wire and getting battery voltage at either end of the wire, even overlayed it. Only when connected to the ECM does it drop to .9v.
Checked harness about 6-8" from ECM for issues. Only issue noted was the big red and smaller red/green wire that splices to tiny red/green wire. Battery voltage at splice, drove 1.5v+ back probing at ECM.
Thoughts? Short to ground? Things to check?
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