Power Output Stage / Ignition control keeps failing and needing replacement.

Hello to all

Mk4 golf, 2000, 1.8t 20v, AGU engine.

This car has Coil On Plug design with 3 wires and a separate Ignition control described as Power Output stage(POS) bolted to a heat sink on the side of the air intake box.

Before this car came to me it had three POS's changed, when it arrived two outputs were not working so I replaced with a new one and replaced the two Coil packs with known working ones from an engine we have here. The new one has now lost three outputs.

The car was sat idling for about 20 minutes and then it began to stutter and eventually stall. It would not restart so I checked for a spark and three of the four were not sparking. This car has some history here www.scannerdanner.com/forum/post-your-re...el-but-no-start.html . This was the getting it running process.

The POS has four control wires from the ECU and one Earth on one side and four control wires going to the coils. I have checked all these wires for a short to ground, positive and each other. The garage that sent this car to me thought that there may be a wiring problem as cylinder two was the output that kept failing.

I have checked the earth point on the cylinder head where the coils have a common earth point and there are no resistance issues. I have not checked this under load as the car does not run, should I check it while cranking. Is this a valid test?

I'm happy to rewire all the control wires and coil power if needed.

Thanks for the last round of help, reading and checking the suggestion was an educational experience.

Thanks in advance for any suggestions this time too

Do you have a wiring diagram for this vehicle ? We didn't get an Agu engine in the states

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Hello Ben

I've been using this page for my reference www.vwcaddy.com/showthread.php?44244-Vw-...ngine-wiring-diagram

Can you see anything worth investigating?

So I am clear the a52 ignition amplifier is what has been replaced as well as the coils? When it loses spark what gets it back ?

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Yes, the A52 ignition amplifier is the part that keeps going. The only way to get a spark back is to replace it. The coils still work just fine but I replaced just to see if it helped.

Hello to all,

I'm back looking at this car, it's sat at the side of the workshop being ignored. I'm looking at replacing the loom that travels either side from the ignition amplifier. That is the trigger wires from the ECU and an earth on one side and four trigger wires on the other side that goes to the coils. Also looking at replacing the top half of the air box just in case the heat sink in an issue.

Should I replace the coil 12v and earth too?

I'm clutching at straws here, being a bit of a parts changer. I can't think what would cause this ignition amp to keep failing.

Any thoughts would be much appreciated

Just an odd ball thought, but what's the charge rate? I'm wondering if the alternator is frying this module.


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I've never worked on one of these, so bear with my ignorance, but is this control module bolted to some kind of heat synch like some of our US model GMs were doing with the ICM on trucks and vans? A dab of dielectric grease would go a long way toward extending the life of those. I don't know if that's relevant to what you're working on though, sorry.

I've been trying to find a video to post with no success... I've been thinking about it since you first posted this thread.
I'm 90% sure it was a lecture video, probably Premium.

Scanner Danner was talking about hall effect cam sensors . I think the example he gave was for a Chrysler.
Hopefully I don't butcher the explanation, but if the hall effect comes to rest in such a position that it would hold the signal to ground, a failing Hall effect could potentially be unable to hold the signal to ground. This would result in spikes, periods of high and low voltage that could trigger the coil much like when Scanner Danner makes a coil fire with a test light.
So you would end up with random coil firing events, key on, engine off.
This would greatly reduce the life of a coil or ICM.

I've seen a similar cam sensor failure on a Camaro with an optical distributer.

KOEO, the CAM signal would cycle high to low, seemingly for no reason (the engine wasn't turning, so the distributer and CMP were stationary as well).

I was never able to difinitively prove that this was the cause, but that car was eating ICMs for breakfast, lunch and dinner!
The poor guy put at least 5 ICMs in that car before he called me in for a second (well sixth) opinion.