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gtsingh91
04-07-2017, 03:30 PM
Weird issue here. B5 1.8TQM AWM 198k miles. I was getting onto the highway today at about 55mph and then the car lost power and stalled out with the yellow EPC light on. No CEL. I let it sit for a couple minutes and started it back up and it drove perfectly fine back home still with no CEL (40 miles away). This happened once before a few months ago and has since never happened until today. I was planning on doing plugs/coils as a maintenance thing in the near future. Any suggestions?

gtsingh91
04-07-2017, 05:52 PM
Just did some research and others with similar situations said that it could be the crankshaft position sensor (engine speed sensor). I'll order a new one and see if that helps.

elduderino200
04-07-2017, 06:31 PM
One day mine wouldn't start for seemingly no reason and it ended up being the crank position sensor. Luckily for me it never stalled mid drive but I have heard it can.

RENOxDECEPTION
04-10-2017, 01:57 PM
When my EPC light (electronic power control) was on/flashing it was a broken wire on the connector to the throttle body.

Check throttle body, throttle pedal, and wiring between them.

gtsingh91
04-14-2017, 07:54 AM
Anyone know how to get a stripped hex screw out from the engine speed sensor [headbang]

walky_talky20
04-14-2017, 08:01 AM
First, I'd go at it with a chisel and hammer. Hit it on the side first (perpendicular to the bolt shaft). This will put a mild stretch on the bolt and help to loosen. At that point you can try to pound a slightly larger torx bit into it. Or just try to drive the bolt head counterclockwise with the chisel.

2nd option, pound a 12-point socket over it. Then loosen.

Or vice grips. Or left hand drill bit. Or weld a nut to it. Or cut a slot in the head with a grinder and use a huge screwdriver. Lots of ways.

If at any point you think the bolt is going to snap before it breaks loose, put some heat on it. Heating around the bolt hole is preferable to heating the bolt itself.

gtsingh91
04-23-2017, 07:31 AM
Got the sensor out. Replaced the OEM CPS with a new Bosch unit. The car drove fine for about 500 miles until yesterday it cut out again going about 55mph. CEL and EPC lights came on and threw a p0688 code. Some other threads point to the ECM relay going bad. You guys suggest picking one up from the dealer for $20 or is there something else I should look at?

gtsingh91
06-25-2017, 02:00 AM
This problem happened to me again a couple times. It randomly shut off on the highway, left no CEL just an epc light. When scanned for codes, nothing came up and the car started right back up and drove fine for another 600 miles or so until this morning. Happened again at a light near my home but this one threw a P0688 code. Started right back up and drove fine. I didn't clear the light this time because I wanted to remember the code, which happens to be the same one it threw last time. I haven't changed or checked the ECM relay since the last time this happened because, like I said, the car drove and drives great otherwise. Is it safe to assume the ECM is the culprit? Or ECM relay? I think I'm going to inspect and replace my coil harness since it looks brittle and change the relay out. Car drives perfectly fine with the exception of this. Smooth, no power cuts, no lights nothing.

Corrado_Guy
06-25-2017, 08:43 AM
I had a similar problem but usually when it was wet out or I would get missing on high boost and generally no codes. On mine it was because the MAF connector was changed before I owned the car and it was done with butt connectors and heat shrink. I cut the butt connectors out and soldered the joints then used heat shrink and the problem never came back. It was similar in the sense that it would randomly happen but usually it was wet out which was the only common point for me.

gtsingh91
06-25-2017, 09:14 AM
I had a similar problem but usually when it was wet out or I would get missing on high boost and generally no codes. On mine it was because the MAF connector was changed before I owned the car and it was done with butt connectors and heat shrink. I cut the butt connectors out and soldered the joints then used heat shrink and the problem never came back. It was similar in the sense that it would randomly happen but usually it was wet out which was the only common point for me.

Would it throw any codes? Or just nothing? When it happened a couple times it threw no codes (stored either) but two times it threw the p0688 code.

Corrado_Guy
06-25-2017, 11:57 AM
It threw codes once and it was random mis-fire codes and something else but it was only once. All other times there were no codes but the car would crap out on a hard launch but did not stall out. The MAF is right by right front tire so moisture can get in there on my setup, not sure about stock. Not sure what code you have, a P code is a generic code so I would have to look it up.

gtsingh91
06-25-2017, 07:15 PM
I took a closer look today and I think I can rule out my MAF since I'm not getting any kinds of misfires or anything on full boost. The car runs perfectly fine, with the exception of this random stall every couple thousand miles or so, then starts right back up. It seems like it's an intermittent issue with the ECM relay and many threads have pointed to 3 suspects in my situation: 1). a short in the coil harness causing a, 2). blown fuse 29 or, 3). faulty ECM relay.

Fuse #29 was not blown. It seems like the previous owner already changed the OEM coil harness to a newer one since the harness was cut and had heat shrink on it with electrical tape over it. I took the old tape off and checked the connections under the heat shrink and put new electrical tape over the connections then secured it tighter with a zip tie so it wasn't "flapping" around. I removed the ECM relay (#30) and it didn't look corroded or really bad (just old after 203k miles I guess) so I cleaned the contacts, reinstalled it, then cleared the P0688 code. Took it for a spin and drove it through many cycles without a hiccup. I will see how it goes from here and go to the dealer tomorrow for a new ECM relay. $20 can't hurt. If this doesn't work, I'll be digging deeper into the coil harness.

Scottfree
06-27-2017, 05:24 PM
Had a similar problem with shutting down. One guy on a thread said CPS. They get hot and shut down. Sprayed some carb cleaner (freon)on it last time and it fired right up. Replaced CPS and it runs great since.

gtsingh91
06-27-2017, 05:57 PM
Maybe the new Bosch CPS I installed could be faulty? I just don't see why it happens so randomly with no pattern at all. I'll pick up a new ECM relay and keep it for the next time it happens, as that's the code it threw. If that doesn't solve my issue then I'll look at swapping out my CPS for another one.