Cranks but won't start randomely EPC/Battery light

21143 Views 15 Replies 8 Participants Last post by dublove88, Aug 22, 2015

Just4Kicks

Discussion Starter · Jun 30, 2015

Car won't start randomly. Usually on short drives after I park but it could happen at any given time. Happened a few times while driving or at a stop light to. This is insane as Ive forked out so much money already, (not for this specific issue) what is life? its a 2000 Passat 1.8t ATW. One time I was going about 90 and my car lost power, epc light and battery light came on as I started to pull to the side of the road it regained power and I got back up to speed. Im not having any electrical problems with windows or lights, only thing I notice is when I roll windows up to the top and keep trying to roll them up, as I pull up on the buttons, the car idle jumps a lil bit... but Im pretty sure its always done that. Well the light inside the trunk doesn't work and the "boot lid open" indication on dash don't ever show up but I haven't been able to link that to the car not starting, cranks all it wants, just won't turn over. Any ideas? Alternator checked and good, timing belt recently done, battery should be good, MAF replaced with BOSCH, Premium gas always used, driver door lock module replaced... Sometimes I get it to start by undoing the battery terminals for a while but not always a solution.

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John_E

· #12 · Aug 9, 2015

FrescoGreen01.5 said:
This is classic Crank Position Sensor (ESS) failure behavior. It doesn't die, it just gets flaky. Replace it.

If you have a crank/no start again, try this: crank for 7 seconds continuously. If the ESS wasn't giving a signal, the ECM will go in to a limp mode after 5-6 seconds and go ahead and start without the ESS. The EPC light will be on and the idle will be higher than usual, but it will run and drive ok. Much better than being stranded.

Thanks for the tip. My elder son has been going through this with his 2002 A4. I didn't know about the 7-second rule, but he may have been doing that subconsciously.

Anyway, I bought him an ESS, and this morning he and his brother finally got around to installing it. Their advice for an AMB 1.8T is to drive up on the ramps and have one person under the car and one above it while threading the ESS lead down from the plug-in point under the coolant recovery tank. They were done with the remove-and-replace in less than 30 minutes.

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John_E

· #15 · Aug 12, 2015

Tomvw said:
Did you get this fixed ?
Your issue is typical of a faulty ECU power supply relay.

Good point -- been there, done that, as well.

In hindsight, our first warning of a failing ECU power relay was a couple of strange CEL codes, but it did not throw any codes when it finally failed.

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