My car died at a local autocross last weekend and i can't figure out what's wrong. It will turn over but die immediately. I've checked the sensor read out on the PFC and they are way out of whack.

PIM 0.03
VTA1 0.01
VTA2 0.01
VMOP 0.00

I installed the stock ECU and it fires right up and idle ok. I've removed the airpump so it's not perfect but ok.

I tried replacing the TPS in hopes that it would make some difference but it doesn't. I've also tried disconnecting the map and tps to see if the reading change and they do read that they are disconnected.

Any ideas?

 

Are you sure you didn't have a loose ECU plug or something? Check the harness. If you send your PFC to Apex'i you will be waiting on it for months.

 

pop the cover on your pfc check for any burnt traces. that usually only happens from a bad wiring harness or loose connection like arghx said

 

Popped off both covers on the PFC but I don't see anything. The wiring harness on my car is only a few years old. So I don't think that would be the problem.

 

Check fuses.

 

The fuses all look good.

When I step on the throttle the readings change slightly.

PIM 0.04
VTA1 0.03
VTA2 0.03
VMOP 0.00

 

Sounds like an open circuit on a reference voltage wire.

 

Why would it run on the stock ECU then. That's the part that really has me puzzled.

 

Check Pin 4D on the PFC board. It may have broken or had a bad solder joint. Or the wire to the connector for Pin 4D.

 

I double checked the PFC board. It looks good. I also checked the connector. It also looks good. Still not working.

 

I think I may have tracked it down to 3I pin. I only get .03 signal out of it. Does it make sense that it's the problem?

 

I had the same issue with a PFC I had once. I had an electrical engineering friend look at and he said all those sensors share a common ground within the PFC and when it goes bad, it will not read voltage from those sensors (obviously).

 

Did a new PFC fix the problem? Did you have any issues since the new pfc?

 

Yes, I replaced the PFC with a brand-new unit and no problems, been running fine ever sense.

General rule of thumb is; if the car won't start on the PFC, but will run fine on the stock ECU, then you have a bad PFC. This, of course, isn't taking into consideration a tune so horrid it would prevent your car from starting, but I highly doubt this is your case.

I will call him and see if he remembers how to fix it, it said it wouldn't be too bad if I recall.

 

Just called my engineer friend...

He said most likely it's a bad 5v regulator internal to the PFC. Should have part #7805 (generic part #) or circuit IC18 on the PFC main board, usually a 3-pronge chip on the board (with a tab on the back to bolt to the board/chassis).

If you can de-solder the chip and remove it, solder it back in, it should only cost you $2 for the part.

 

Thanks for the info. I think I might get another PFC and send mine in to Apexi to get fixed then sell one of them. I can't be without my car for 3 months and i don't trust my soldering enough to do it myself.

 

Progress update: Got a new (used) PFC. Installed it. Car ran great. Today coming home from work it dies again. Same thing. Same from the sensors. I put in the stock one again and it started right up.

Does this mean I have a short? I take it I need to track down the short and get another PFC? How do you go about tracking down a short?

 

Have you checked your Alternator output?

With the stock ECU, fire up the car and measure the output of the alternator to ground while revving to 3krpms. The output voltage should be ~12.6-13.8V. If you are seeing anything higher than 14V then the alternator most likely killed the PFC. I have seen a bad alternator feed up to 18V which killed the battery and knocked out a PFC.

Worth a shot taking a look. I am not to sure it would be a short, considering it runs with the stock ECU.

Have you already sent the first PFC to apexi? They may be able to help you determine the root cause of failure.

Good luck

 

I'll check that tomorrow.

I've haven't sent in my PFC yet. It's good I waited. Now I can save on shipping by sending two at once.

 

I just checked the alternator. It seems to be good. Any other ideas of things to check? I appreciate any ideas.

 

Check the wiring harness under the front drivers side wheel well, I burnt though a few wires in this location and it took out my PFC

 

I haven't updated in a while. This was the problem. Now I just need to get another PFC.

 

I have mine out for repair at a local shop that rechips ECU's, I'll let you know if this works out, may save you a lot of time and money.

 

I broke down and sent my two fried ones to Apexi. They said it typically doesn't cost more than $150 ea to get repaired.

 

When I contacted Apexi about repairing a malfunctioning PFC I was told if the repairs exceeded $300 I would simply be given a new one.