Engine cuts power and PATS light come on

wow, I had the same results trying to diagnose my car. With a diagnostic unit hooked up everytime the issue occurred the pcm lost power and the diagnostic unit wouldn't be able to give any info other than the pcm lost power.

Since a 3L swap was done I'd check the connections to the PCM, the 3 large clips on the pass side and the one main on the driver side. Just make sure the bolts are tightened all the way.

all my connections were solid, the thing I thought was causing it was my ps leak. It had covered the 3 connectors on the passenger side. I thought it may have been acting as a conductor and bridging some wires. That was all cleaned with a wire safe cleaner and carb cleaner and dried and lihtly wrapped with a rag to keep any more fluid from penetrating the connectors. (it didnt get in the connectors, just on them) but that didnt cure the problem.

todras said:

Since a 3L swap was done I'd check the connections to the PCM, the 3 large clips on the pass side and the one main on the driver side. Just make sure the bolts are tightened all the way.

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We checked the connectors, bolts are fine on it. I think he should return the PCM to stock, run it in his other 00 SVT and see if its the computer. It will help eliminate things.

I'll swap them out later today. It is just SOOO weird that the PCM is not DEAD, it just looses power at the SAME RPM only under load... I should also mention that I had an 02 sensor showing 0 volts, but of course no CEL for it, and I do KNOW that the CEL works. Could that be from a MIL eliminator or the A/F gauge?


Posthuman- Care to share what WAS the problem with you car, or are you still trying to figure that out?

The lower 02 sensors were turned off with the tune. Also, there are 42# Cobra injectors, so the stock tune will only result in the car stumbling at idle. The 3L swap was done back in 2003 if that helps. It ran flawless the entire time I owned the car(since new, and throughout the entire 3L swap). I sold the car to svt2sho in April/May of 2007, so it's been out of my hands for well over a year now. I never had even the slightest of these issues. I replaced the TPS with a brand new one, due to my own fault, having installed it wrong, and it snapped the tps. Once the new one was in, everything was perfect. That was probably a year before I sold the car. Regardless, the upstream 02 sensors were basically brand new as of late 2006, early 2007, I can't remember. But Jim(beyondloadedSE) and I replaced them when we cleaned out the intake manifolds and plugs/wires. I hope this is useful.

Mark

TX00SVT said:

I'll swap them out later today. It is just SOOO weird that the PCM is not DEAD, it just looses power at the SAME RPM only under load... I should also mention that I had an 02 sensor showing 0 volts, but of course no CEL for it, and I do KNOW that the CEL works. Could that be from a MIL eliminator or the A/F gauge?


Posthuman- Care to share what WAS the problem with you car, or are you still trying to figure that out?

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if I knew I'd share but I'm still trying to fix it myself. Curious to see what happens with the harness or PCM swap

Ok, well, I pulled the PCMs and swapped the 3L into the 2.5, but now I can't get the 2.5 to start. The 2.5's ignition won't work with the 3L's key, and when I turn it to "ON" with the 2.5 key, the PATS light just flashes at me. It's a 2000, so I believe that means it has PATS integrated into the PCM. Todd suggested taping the 3L key to the PCM, which I tried, but it did not solve the problem. Is there anything else I can do besides trying to dig the chips out of the keys or having a key cut to my 2.5's ignition and programmed to the 3L's PCM? I really don't want to spend $50+ for a key just to drive the car for 20 minutes to see if the PCM is fried. Can I bypass PATS or just have a key cut, but not programmed (assuming that the other chip being in the ignition, even though the right key is in the car, is screwing things up)? I know that people have swapped PCMs before...what am I missing?

to swap pcm you will need to either program the other cars keys to the pcm or swap the chips in the keys.

having two pats keys together in the ignition isn't helpful either.

also if you want to leave the key in the car to work pats you need to put it in the steering column next to the pats antenna.

So can I just pull the chips out without messing anything up? They are removable?

EDIT: After cutting my thumb almost to the bone trying to get this flap off of the key, I think I'll save myself a $75 trip to the ER for stitches, and buy a $50 key.

Ok, as usual, I'm trying to be a cheap ass here. Can I have a non-chipped Ford key cut to match my 2.5's ignition, and just hold my 3L key to the PATS antenna in the column? I did a lot of searching and some people say that it works while others say that it doesn't. Otherwise, how hard is it to swap the ignitions? I'm assuming almost impossible... I can't for the life of me get either of my keys to open up with a small flathead screwdriver and a knife. :blackeye:

TX00SVT said:

Ok, as usual, I'm trying to be a cheap ass here. Can I have a non-chipped Ford key cut to match my 2.5's ignition, and just hold my 3L key to the PATS antenna in the column? I did a lot of searching and some people say that it works while others say that it doesn't. Otherwise, how hard is it to swap the ignitions? I'm assuming almost impossible... I can't for the life of me get either of my keys to open up with a small flathead screwdriver and a knife. :blackeye:

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yes you can use a non-pats key to work the ignition and hold the pats key next to the anntenna. works fine. I did this for a few weeks with my 99 when I swapped the ignition cyclinder with my 95 when the one in my 99 failed.

PATS only reads the key when turn the key to the run position before or as you are starting the car.

I finally got around to taking the GF's car to Walyworld and had a non chipped key cut for my 2.5's ignition. I drove the car around for about 45 minutes and probably covered 20+ miles. The car drove like normal and pulled to the redline several times. I had ZERO issues with losing power, and no PATS issues.

Back to square one. Is there ANY way that the problem could be with the tune since it seems to run fine in stock form? The grounds appear to be fine, the TPS tests good, etc. The wiring in the car that I have inspected is all in excellent shape, including the PDB. The previous owner mentioned that the IMRC likes to come out of gear, which would make sense since the problem always seems to occur at that point, but how does the PATS light play in? I don't remember it ever coming on in my other SVT when the pump was going out. Starjammir felt that the fuel numbers looked fine when we were datalogging and the car has 42# injectors with an FSVT pump, so it should have WAY more fuel than it could ever need.

What next? Put the PCM back and swap the IMRC? New harness? New plugs and wires? Replace the already newer TPS and connector with new ones for the hell of it? Do I dare put the 2.5's PCM in the 3L? Swap the injectors and try running the 3L on its stock tune? Could a dealer even help me at this point?

Maybe power to the PCM or ground to the PCM, but why only at 3800.

I'm thinking a dealer is not the way to go on a moded car. You will be in worse case with a very large bill. If they would even touch it. I'd get a new tune for starters since it's fine w/o it.

I think he put the 3L computer into the 2.5 but I could be wrong. I dont think its the tune due to it being on another tune he has too.

I changed my tunes and even reloaded the tunes to the XCAL in case they were "corrupted" or something.. never helped me, either.


I am CONVINCED it is either a VREF or ground issue. pull the ignition cover around the steering wheel and jump across the ignition.. (use a meter and see which pins are made when the car is in "off", "on" and "start" mode.. then jump from the constant power pin to the "on" so that even if the ignition is "OFF" its still sending the voltage out the "on" pin (as if the key were in the ON position...) You can turn the key off and remove it with the car still running in this manner and it will eliminate a faulty or flaky pin or ignition module...

other than that... you've got a VREF/ground issue man... no ifs ands or buts from me..

It just really confuses me that its always at 3800 RPMS and not all the time. Another thing that leads me to either a computer, power to the computer or ground on the computer is that the xcal showed error source lost.

Well, I took the 3L's PCM back out of the 2.5, put everything back together and tried running the 3L again. I uploaded my mild tune, and let it sit and idle while I was putting the cowl back together and picking up tools. I took it for a test drive and with the exception of once while rolling out of the gate (revved slightly with the clutch in), the PATS light stayed off, and the car would go though the full range. I drove it around for maybe 10 miles on the city streets, then my GF wanted to stop at a friend's house on the way home, so I did. As soon as we pulled out of the driveway there, SOB, the issue was back. :help:


Besides wiring obviously , the only other thing that I could try to pin this on is the fact that the car has an older aftermarket Viper alarm system that also seems to have gone haywire since the bucking started. When we went over to our friends' house, I made sure NOT to activate it, but rather to just press the lock button on the door and open it back up with the key, but obviously I still had the problem afterwards. When I say that it went haywire, I KNOW for a fact that it worked before this stuff started because I accidentally set it off on myself twice when opening and closing the trunk with the key (alarm fob doesn't do it :nonono. The proximity/motion sensor sent out a warning chirp when I opened the lid, and set the alarm off when I closed it. I seem to remember that when I first got the car, the little light flashed sort of like the PATS light, and now instead it is on solid whenever the ignition is off. Now the alarm doesn't go off when I mess with the trunk, and I've actually tried setting it off by rocking the car back and forth with it on, with no success. Also, it doesn't chirp at me when I lock/unlock the doors anymore like it did. I suppose the speaker could have gone dead, but somehow I don't think so. The alarm is a little quirky in the fact that the lock button on the remote both locks and unlocks the doors, and none of the other buttons seem to do anything. I had the panel under the steering column off the other day and all of the connections going into the box where connected at that point, but there is about 8 miles of wires under there, or so it seems. Is anybody knowledgeable about car alarms on these cars and whether or not they could potentially cause these symptoms? Should I have it removed to be safe?


Ray- I will try to hit up a junkyard and steal some TPS and DPFE plugs tomorrow for the hell of it and check out the ignition, as well as try to make sense of my wiring diagrams that I have.

It's a possibility that your alarm may cause some symptoms but not at a specific RPM. The Light staying on constant with the key off usually means your alarm is in Valet mode, which will also disable the chirp and possibly some functions other than the lock and unlock. I don't think the 2 are tied together but if you really think about it, if your alarm isn't in valet mode and did crap out at the same time, it's a possibility that your wire problem may be in that general area. Stripped wires touching, insulation rubbed off from vibration, wire to disable the starter stretched from engine movement and grounding. These are all possibilities, but the alarm causing the problem would have symptoms more like your car doesn't start period, no crank, engine won't turn, no nothing except dummy lights.

I may be wrong as I am not 100% familiar with the SVT PATS but I know most aftermarket alarms wouldn't cause your symptoms.