b5 s4 won't start, ECU problem?
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Joined: Jul 2011
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b5 s4 won't start, ECU problem?
Hello, all.
Quick rundown of symptoms:
A week ago, the car died shifting into 2nd from a stoplight. just completely cut out. Electronics were there, radio, AC, etc, just engine went pfft. Coasted it into a parking spot on the side of the road, and it wouldn't start again. Walked home, grabbed my netbook, walked back, and dumped codes. The important ones were:
18258 - Powertrain Data Bus: Missing Message from ECU
01314 - Engine Control Module: No Communications
After I dumped them, I cleared and rescanned, no codes left. On whim, I tried starting it again and...it started. Drove it home. Over the next week, I've cautiously driven it in the neighborhood and it didn't die. It acted like it wanted to die sometimes, the idle RPMs would drop and it'd be about to stall, with the ABS and the traction control lights coming on..but I could save it by giving it some throttle.
It died again two days ago in front of my house (was actually about to leave and it went out before I could pull away). I scanned again, same codes, cleared them and it started back up. Tried driving to the store several blocks away, but it again died at a stop sign. Pushed it to the side of the road, scanned, cleared it started again. I moved it twenty feet into a parkable spot and left it over night. Went back today to investigate. Based on some research I did, I checked under the passenger's floor mat for water, and sure enough, it is soaked. Pulled the window seals from the engine bay, pulled the battery and the whole area was full of gunk, the drains off the freshair filter assembly were clogged; it was a mess. Cleaned all of that out.
The research I did suggested the TCU might be flooded, causing the problems I'm seeing. Thing is, I can't get the carpet out enough to actually get at the TCU pod (or at least, what I think is the TCU pod, plastic box immediately fore of the seat mounts, slightly left of center of the passenger seat centerline). I can really start yanking on it, if that's what it takes, but wanted to run all of this by the board.
The last bit of info is that once I reconnected everything today, I scanned again, same two codes...except this time they wouldn't clear. Each scan gives me 18258 and 01314. Go into the individual controllers, scan it, clear, scan, they stay there.
I have a spare ECU around. It took some shock damage from a jump a while ago, but it should still work. I can swap that in if it buys me anything. Anyone have any ideas?
The Ross-Tech site lists some version of a problem with the CAN-databus as a possible cause for each of these codes. Is there a common point of failure I should check? The wiring of this car has me a little mystified, can anyone give me any specific pointers on what to check?
Any help is much appreciated. I wouldn't mind not being able to go to work on Monday, but my boss might be getting tired of it.
Quick rundown of symptoms:
A week ago, the car died shifting into 2nd from a stoplight. just completely cut out. Electronics were there, radio, AC, etc, just engine went pfft. Coasted it into a parking spot on the side of the road, and it wouldn't start again. Walked home, grabbed my netbook, walked back, and dumped codes. The important ones were:
18258 - Powertrain Data Bus: Missing Message from ECU
01314 - Engine Control Module: No Communications
After I dumped them, I cleared and rescanned, no codes left. On whim, I tried starting it again and...it started. Drove it home. Over the next week, I've cautiously driven it in the neighborhood and it didn't die. It acted like it wanted to die sometimes, the idle RPMs would drop and it'd be about to stall, with the ABS and the traction control lights coming on..but I could save it by giving it some throttle.
It died again two days ago in front of my house (was actually about to leave and it went out before I could pull away). I scanned again, same codes, cleared them and it started back up. Tried driving to the store several blocks away, but it again died at a stop sign. Pushed it to the side of the road, scanned, cleared it started again. I moved it twenty feet into a parkable spot and left it over night. Went back today to investigate. Based on some research I did, I checked under the passenger's floor mat for water, and sure enough, it is soaked. Pulled the window seals from the engine bay, pulled the battery and the whole area was full of gunk, the drains off the freshair filter assembly were clogged; it was a mess. Cleaned all of that out.
The research I did suggested the TCU might be flooded, causing the problems I'm seeing. Thing is, I can't get the carpet out enough to actually get at the TCU pod (or at least, what I think is the TCU pod, plastic box immediately fore of the seat mounts, slightly left of center of the passenger seat centerline). I can really start yanking on it, if that's what it takes, but wanted to run all of this by the board.
The last bit of info is that once I reconnected everything today, I scanned again, same two codes...except this time they wouldn't clear. Each scan gives me 18258 and 01314. Go into the individual controllers, scan it, clear, scan, they stay there.
I have a spare ECU around. It took some shock damage from a jump a while ago, but it should still work. I can swap that in if it buys me anything. Anyone have any ideas?
The Ross-Tech site lists some version of a problem with the CAN-databus as a possible cause for each of these codes. Is there a common point of failure I should check? The wiring of this car has me a little mystified, can anyone give me any specific pointers on what to check?
Any help is much appreciated. I wouldn't mind not being able to go to work on Monday, but my boss might be getting tired of it.
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