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VW ECM testing and repair

#1 User is offline   Steve_Voisinet Icon

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Posted 24 August 2015 - 07:20 PM

My 1997 VW Cabrio 2.0 (ABA engine code) would crank over but not start. It had no spark. I found that the coil was not getting a trigger from the ECM. I installed a used ECM and the car ran great for about a week, then it quit again. It now has the same problem - No trigger to the coil. The crank sensor and camshaft position sensor ohms test good and seem to provide a good output.

Does anyone know what might be causing the ECM to fail this way?

Does anyone know any good place to get an ECM tested and repaired? Auto Zone wants $600 for one.
www.circuitryrepair.com claims they can do it for $175, with free testing.
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#2 User is offline   OLDGOLD Icon

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Posted 24 August 2015 - 08:07 PM

View PostSteve_Voisinet, on 25 August 2015 - 11:20 AM, said:

My 1997 VW Cabrio 2.0 (ABA engine code) would crank over but not start. It had no spark. I found that the coil was not getting a trigger from the ECM. I installed a used ECM and the car ran great for about a week, then it quit again. It now has the same problem - No trigger to the coil. The crank sensor and camshaft position sensor ohms test good and seem to provide a good output.

Does anyone know what might be causing the ECM to fail this way?

Does anyone know any good place to get an ECM tested and repaired? Auto Zone wants $600 for one.
www.circuitryrepair.com claims they can do it for $175, with free testing.
cant you switch mags Lol there use to be a ecm company in florida that would do ecms for 125 all you had to do was send them your VIN. Have you done any wiring sensor checking?normally crank sensor sends pulse to ecm to trigger coil output ?high resistance,open wire in harness ,short taking out the coil driver in ecm.Or transient voltage spiking it.?
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#3 User is offline   mod911 Icon

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Posted 25 August 2015 - 08:40 AM

The coil driver should be one for each cylinder. SO a no start usually isn't all 4 bad. Ohms testing is NOT sufficient to find bad parts ususally,drivers not completely grounding need lab scopes and fast one at that. Cam sensors or crank sensors erratic or signal loss because of chafed,chewed,corroded or oil soaked wires is possible. Sounds like fun,have a-z diagnose it for you.....lololol.....an 0-2 sensor or 2 will solve it.....lol
Bad grounds and low current flow would be on my list to check. What does scan show? Does it have good square waves from crank and cam sensors AT ecm? ANY other problems?
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#4 User is offline   Steve_Voisinet Icon

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Posted 26 August 2015 - 07:10 PM

Right now I wish this car had a mag! :)

I do buy some parts from Auto Zone, but I am not the guy in there asking for advice. lol


This car only has one coil, with a distributor. So the ECM only has one coil driver, right?

I don't have access to a scope. I have checked the cam and crank sensor output at the ECM with a LED test light, and it shows a good signal as far as I can tell. I have checked, and cleaned the grounds.

It does occasionally set a PO341 code (camshaft sensor) while cranking.

The fuel injectors are getting a signal.
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#5 User is offline   mod911 Icon

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Posted 28 August 2015 - 10:33 AM

Old style stuff there. If you have injection the crank and cam sensors must be working. Maybe check the coil for shorts or open primary circuit. Put test light across coil connector and see if it flashes. It may be weak cranking but if it does light it is probably a bad coil or maybe open coil wire but sparks usually fly some where if that is so. The cam sensor and temo sensor share a ground so see if engine temp is correct in ecm data....A loose t chain or stuck cam phazors or tensioner will cause cam sensor code if the timing does not line up with crank sensor signal. There is a control module under the coil assm, its all one piece it look slike so maybe there is the problem. They are cheap so buy one an try it.
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#6 User is offline   Steve_Voisinet Icon

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Posted 29 August 2015 - 05:50 AM

Thank you Dick. I will take a look at that when I get home in a couple of days.
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#7 User is offline   Steve_Voisinet Icon

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Posted 02 September 2015 - 01:06 PM

I replaced the coil/module. That did not help. I then replaced the ECM again and Viola - I now have spark and the engine runs. I am thinking that maybe the old coil/module was drawing too much amperage and fried two ECM's? I haven't driven the car yet. I REALLY hope it doesn't smoke a third ECM!
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