Having some electrical problems
Thread Starter
TECH Junkie
Joined: Nov 2001
Posts: 3,987
Likes: 0
From: Melbourne, FL
Having some electrical problems This is driving me crazy. It started Wednesday night at the track. Out of nowhere, my idle will not go below ~1900rpm, and the fuel level gauge shows the tank as empty (when it's not).
Here's where the strangeness comes in. With the car running (and ATAP monitoring), my TPS goes crazy and fluctuates between 12%-35% open @ idle without me touching the pedal. It does the same exact thing with the engine not running while priming the fuel pump. With the key on, and car not running, the TPS is usually fine, but does occasionally show a false reading. The throttle blades are closed, and I have swapped in another TPS sensor for testing, so those can be ruled out.
Occasionally, ATAP will report that it has lost communication and I have to hit (R)etry, then it resumes as if nothing happened. Also, the fuel level gauge will sometimes jump all the way up to full, or 3/4 tank for no apparant reason.
It has to be something common to both of these circuits, and may be affecting more than what I have noticed at this point. The car still runs fine though, just the high idle and fuel gauge issue as far as I can tell. I completely removed the engine harness and inspected it last night, and found nothing out of the ordinary.
The PCM ground wires behind the driver side cylinder head look alright, however, after I put everything back together and turned the key on, the SES light flickered and the fuel pump continuously ran with the key on/engine off, as if there was a bad ground. I'm going to pull the harness off again and redo all of the ground connections in it in case there's a broken wire near one of the ring terminals (they are kind of kinked/twisted looking).
If the ground wires don't turn out to be the culprit, I need some serious help here. I have not traced the wiring back to the tank (for the fuel level sender) but I doubt the problem is there because of the other symptoms.
Can anyone offer some insight here? I'd like to race this weekend, but will not take the car out until it's fixed.
Here's where the strangeness comes in. With the car running (and ATAP monitoring), my TPS goes crazy and fluctuates between 12%-35% open @ idle without me touching the pedal. It does the same exact thing with the engine not running while priming the fuel pump. With the key on, and car not running, the TPS is usually fine, but does occasionally show a false reading. The throttle blades are closed, and I have swapped in another TPS sensor for testing, so those can be ruled out.
Occasionally, ATAP will report that it has lost communication and I have to hit (R)etry, then it resumes as if nothing happened. Also, the fuel level gauge will sometimes jump all the way up to full, or 3/4 tank for no apparant reason.
It has to be something common to both of these circuits, and may be affecting more than what I have noticed at this point. The car still runs fine though, just the high idle and fuel gauge issue as far as I can tell. I completely removed the engine harness and inspected it last night, and found nothing out of the ordinary.
The PCM ground wires behind the driver side cylinder head look alright, however, after I put everything back together and turned the key on, the SES light flickered and the fuel pump continuously ran with the key on/engine off, as if there was a bad ground. I'm going to pull the harness off again and redo all of the ground connections in it in case there's a broken wire near one of the ring terminals (they are kind of kinked/twisted looking).
If the ground wires don't turn out to be the culprit, I need some serious help here. I have not traced the wiring back to the tank (for the fuel level sender) but I doubt the problem is there because of the other symptoms.
Can anyone offer some insight here? I'd like to race this weekend, but will not take the car out until it's fixed.
Re: Having some electrical problems Sent ya email, George. Sure sounds like an electrical gremlin in the wiring harness... Burned wire (you got a new harness after the incident, right?)? Bad ground? Hmmm....
-Andrew
-Andrew
Thread Starter
TECH Junkie
Joined: Nov 2001
Posts: 3,987
Likes: 0
From: Melbourne, FL
Re: Having some electrical problems Well, I have made some progress, but still don't know what's going on...
I have found that if I disconnect the wire that sends the fuel level signal to the PCM, the problem goes away (obviously the fuel level gauge won't work this way, though). The problem appears to be somewhere between the terminal block I have near the fuel pump and the PCM itself.
For now, I just have the fuel level signal disconnected near the tank. Sometime in the near future I'll take the interior out and start troubleshooting the wiring harness that runs underneath the carpet...
I have found that if I disconnect the wire that sends the fuel level signal to the PCM, the problem goes away (obviously the fuel level gauge won't work this way, though). The problem appears to be somewhere between the terminal block I have near the fuel pump and the PCM itself.
For now, I just have the fuel level signal disconnected near the tank. Sometime in the near future I'll take the interior out and start troubleshooting the wiring harness that runs underneath the carpet...
Re: Having some electrical problems Pcm controlls fuel gauge, it needs to know fuel level in order to control & check evapative emission system. Check that wire you disconnected from sending unit w/engine running & make sure there is no stray voltage. You checked all grounds right? at pcm no more than 10 milli-volts runing any pcm ground. Pcm can be your problem it's gonna take some through diagnostics to pinpoint your problem ,GOOD LUCK.
