A4 (B5 Platform) Discussion Discussion forum for the B5 Audi A4 produced from 1995-2001 B5 FAQ

Bad ECU?

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Old May 26, 2007 | 08:17 PM
  #1  
kerrybr's Avatar
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Default Bad ECU?

I think my ECU is dead. The engine will turn over but it won't start... and it was working fine yesterday. I tried reading the DTCs with VAG-COM, but it won't connect to the engine module (it will connect to the radio and central locking pump). I'm pretty sure its a bad ECU, but is there anything else I should check before I buy new one?
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Old May 26, 2007 | 08:21 PM
  #2  
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Default check your fuses

also try pulling out the ecu and putting it back in.
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Old May 26, 2007 | 08:53 PM
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Default

Are you chipped? If so it might be a bad solder joint, or bunch of flux left on board.
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Old May 26, 2007 | 11:56 PM
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Default With the ignition on do you see a CEL?

Sometimes unplug and replugging the ECU might work
My APR ECU had the same problem and I had a local
APR rep shop flash the ECU with the newest software
version and it's now working perfect.
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Old May 27, 2007 | 05:43 AM
  #5  
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Default tried pulling the ecu... still won't work

I checked all the fuses and removed and reinstalled the ECU - still nothing.

I have an APR chip and Borla exhaust. The chip has been in there for 4 years, so I don't think that it's a bad solder joint.

Any other ideas?
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Old May 27, 2007 | 08:51 AM
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Default If you know the connector pinoutstart checking for shorts.... Bad wires, etc.

But first of all ground and power pins.
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Old May 27, 2007 | 01:06 PM
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Default Take it back to whom ever did the original install

and have them reflash the ECU with the newest software.
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Old May 27, 2007 | 03:34 PM
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Default

If there's flux on the board, after time it can short things out. Seen it many times years later.
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Old May 28, 2007 | 04:39 AM
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Default Unfortunately, installer is 1 hour away

So a tow out to the installer woild be pretty pricey. Guess I could pull the ECU out, ship it to the installer and "work from home" for a couple days until i get it back.

I'm not sure of the pinouts to check for shorts, but more importantly, I'm not sure I could do anythig if I did find a short.

Maybe I'll just buy an ECU off ebay and send mine in to the installer for repairs.
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Old May 28, 2007 | 07:46 AM
  #10  
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Having a spare ECU never hurts.
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