Checking the Wiring Harness
Thread Starter
Joined: Aug 2004
Posts: 11,258
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From: Pace, FL
Checking the Wiring Harness So, I've had issues with my TPS for a while, ECT, and TCS... which are all feeding off the same circuit from what I can tell.
I was going through the harness today to look for continuity issues and found that I had .5 Ohms or less across the three TPS wires between the PCM side and the sensor side (unplugged battery, unplugged ECT sensor, and unplugged the PCM and TPS). All three wires showed .3 to .5 Ohms. Which is good. I don't have an open circuit.
When I went to check to see if there was a cross between them, I was reading Ohms and not infinity, leading me to believe their is a short in the wiring harness as they shouldn't be linked together.
Is that a correct assumption? I checked the 5V reference (Pin 8 in the Blue PCM connector), TPS Signal (Pin 24 in the Red connector), and the Sensor Ground (Pin 60 in the blue). If that's the case, I have a short somewhere in the harness which is causing my issues even though there appears to be no issue tracing each wire back to the PCM. I plan to check to ground as well, but this was the next step in my troubleshooting and wanted to verify that they should be showing infinity and not continuity.
Can anyone confirm my results?
I was going through the harness today to look for continuity issues and found that I had .5 Ohms or less across the three TPS wires between the PCM side and the sensor side (unplugged battery, unplugged ECT sensor, and unplugged the PCM and TPS). All three wires showed .3 to .5 Ohms. Which is good. I don't have an open circuit.
When I went to check to see if there was a cross between them, I was reading Ohms and not infinity, leading me to believe their is a short in the wiring harness as they shouldn't be linked together.
Is that a correct assumption? I checked the 5V reference (Pin 8 in the Blue PCM connector), TPS Signal (Pin 24 in the Red connector), and the Sensor Ground (Pin 60 in the blue). If that's the case, I have a short somewhere in the harness which is causing my issues even though there appears to be no issue tracing each wire back to the PCM. I plan to check to ground as well, but this was the next step in my troubleshooting and wanted to verify that they should be showing infinity and not continuity.
Can anyone confirm my results?
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
Well, cutting through electrical tape to find a problem is a pain in the *** in the old, crappy harness. I ordered a new pigtail and will simply pin in new wires and create a separate TPS circuit. $10 from eBay. Should help me narrow down any issues...
This may not work because the Anti-Lock Brake system taps off of some of the TPS wires. When you check continuity between the wires, you may be reading the resistance of that Anti-Lock Brake device/circuit:
So, under normal conditions, you could see Ohms between all of the wires with everything unplugged. This is an evil circuit...
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
That's what I was worried about. I still think isolating the circuit isn't a bad idea. Makes it easier to troubleshoot. I know I'm getting crosstalk since I'm seeing 6V on the reference.
You'll still need to maintain that splice into your ABS system, which is somewhere in the wiring harness since it also uses the sensor as an input.
I wonder if there is some odd condition where a bad diode, etc in the ABS module could contaminate the TPS signal? It might be worth isolating once you get the harness apart.
I wonder if there is some odd condition where a bad diode, etc in the ABS module could contaminate the TPS signal? It might be worth isolating once you get the harness apart.
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
Hmm... you think leaving it out would be bad? Just to troubleshoot? If it works without ABS, then I know that's a problem. If it doesn't, then I can probably trace it to the PCM having a bad circuit. People remove the ABS all the time and the car still works... so I think this is a plausible idea... I hope.
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Hmm... you think leaving it out would be bad? Just to troubleshoot? If it works without ABS, then I know that's a problem. If it doesn't, then I can probably trace it to the PCM having a bad circuit. People remove the ABS all the time and the car still works... so I think this is a plausible idea... I hope.
(It's hard enough for us to get by on a 1990's "brain," as it is.)If you get in to re-doing the harness, I would definitely leave out the ABS wires to see what happens first - and then put them back in.
You might also try unplugging the ABS Module to see if your TPS voltage readings tame down at all before you get in to the harness work. If there is an internal ABS fault, that would take it out. This brings up another possibility - you could also have a short in the ABS part of the harness that is causing pain here, also.
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Verdad Gallardo I haven't actually torn in to this part of the harness and played with these wires before. You might move this thread to Stereo & Electronics. The gang there may have some other wise thoughts to share on the subject.
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
I unplugged the ABS and plugged everything back together... 4.99V on TPS. Plugged it back in (or so I thought - ABS INOP light is now on) but I was back to 0% TPS and sitting pretty at 40 IAC hot count with .57V... so I'll close it a quarter turn and get my IAC counts up to 60 or so. But it fired right up, held idle with my SD tune, and drove fine.
Also the brake light is on along with ABS INOP (like the brake light for the hand brake). I assume it's just flaking out all around (thought TCS light was not on?).
I need to clean up the harness. I got into it a foot or so before I realized how much of a nightmare it was going t be. So for now, it seems to be working, until tomorrow?
Also the brake light is on along with ABS INOP (like the brake light for the hand brake). I assume it's just flaking out all around (thought TCS light was not on?).
I need to clean up the harness. I got into it a foot or so before I realized how much of a nightmare it was going t be. So for now, it seems to be working, until tomorrow?
I hate intermittent things. Let's create uneducated conspiracy theories to make us feel better about the situation... Maybe there were dendrites growing across the ABS connector, causing the short and the act of unplugging it caused them to break? https://en.wikipedia.org/wiki/Whisker_%28metallurgy%29
Everything going back to nominal when you messed with the ABS module is interesting... The BRAKE light and ABS INOP should indicate that the ABS system is shut down. If there is a problem in the module, maybe it isn't happening because the ABS system has gone to sleep? I wonder if the short circuit will come back once your ABS system is ready to play ball again?
I can't think of why the ABS module isn't happy, though. That will probably require a scan.
Everything going back to nominal when you messed with the ABS module is interesting... The BRAKE light and ABS INOP should indicate that the ABS system is shut down. If there is a problem in the module, maybe it isn't happening because the ABS system has gone to sleep? I wonder if the short circuit will come back once your ABS system is ready to play ball again?
I can't think of why the ABS module isn't happy, though. That will probably require a scan.
Thread Starter
Joined: Aug 2004
Posts: 11,258
Likes: 146
From: Pace, FL
Tech 2 is the only scanner I can think of that will scan the ABS... right? HPT doesn't.
I am thinking seriously about getting an ABS Delete kit with a line-lock. $185 vs $380 for a new ABS module (if it's that). ABS sucks on the car anyway.
I am thinking seriously about getting an ABS Delete kit with a line-lock. $185 vs $380 for a new ABS module (if it's that). ABS sucks on the car anyway.
It's saved my bacon many times! Maybe your modified vehicle just outperforms that the stock ABS system is capable of handling.
Just give it a few more years and we'll be able to mash up the car and rocket technology coming out of Silicon Valley - we'll be able to stop on a dime!
