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Low output voltage on tps.

cruiser54 said:
Napa carries what they call an "electronic cleaner" IIRC. Better than regular old contact cleaner IMHO.

My favorite is DeOxIt # 5 available online. Expensive and worth it. You'll be fine with the Napa stuff. The simple fact that you're unplugging and cleaning is light years ahead of doing nothing anyway.
Click to expand...

Agree. You cant use it with connectors, but the best "cleaner" is a Dremel with a wire brush attachment. Don't forget the anti-corrosive agent, get it in any hardware paint department.

And don't forget, Old Farts Drool! I mean RULE!
 
Most contact cleaners are safe on plastics. Check the label. I've never had any problem.

Joe will have to answer your question about anti-corrosives. I just use dielectric grease but I live in arid Arizona. Joe lives in an area where most of the population have webbed toes.
 
dakineJ said:
Does the contact cleaner damage the connectors?, and for anti-corrosive, are you talking about Dialectric grease or something like Oxguard?

You are correct sir.
Click to expand...

OX-Gard is a great product, but it is intended more for places where copper and aluminum meet.

You want an anti-corrosive for steel to keep the areas stripped down to bare metal from rusting. That is what you ask for in any paint dept.--Walmart, ACE, like that.

Good luck.
 
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Ok, so I got a new ground for the back of the head and cleaned the dipstick ground really good and shiney. Sprayed corrosion remover and after cleaning sealed with anti corrosion spray. Still get 3.4v at tps:-(
 
You got a set of jumper cables laying around? Tey attaching one end of a cable to the batt neg post and the other to the chassis somewhere so the ground doesn't have to flow through tthe block. Then take a reading.Got more than one volt meter so you can compare?
 
ok, got a little further in my investigation today. I tested the positive wire B on the square plug at TPS, i put a red positive lead from the voltmeter to it and connected black to a known good ground on the head and got a pretty good 4.6V. However when i put the black test lead to the connector C, which itself should be a ground the voltage went down to 3.9V.

What is going on? What should be my next step? Is my TCM bad? Is it the wiring that is most likely at fault. how do i test for this?
 
"A" positive to "D" ground--that should be your reference voltage--what do you get measuring that way?

Back probing the connector attached to the TPS "B" positive to "D" ground is your output voltage--what do you get measuring that way?
 
Hook your meter up just like you last had it. Set it where it is easily seen. Start wiggling harnesses that you suspect and watch for the ground to improve.

If you haven't already done this, I would suggest unplugging every connector I could find in the engine compartment and flushing it with contact cleaner and reconnecting.

Why do you suspect the TCU in particular?

It would be great to know for sure where the C connector grounds to and where it travels in the harness.
 
joe_peters said:
"A" positive to "D" ground--that should be your reference voltage--what do you get measuring that way?

Back probing the connector attached to the TPS "B" positive to "D" ground is your output voltage--what do you get measuring that way?
Click to expand...

I am stupid and meant D not C.

So here is exactly what I get: when I connect voltmeter to B and D on the square connector i get 3.9V. If i take the neg from the volt meter and jam it into a known good ground I get 4.6-4.7v. When i do back probing A and D I get 0.14v.

cruiser54 said:
Hook your meter up just like you last had it. Set it where it is easily seen. Start wiggling harnesses that you suspect and watch for the ground to improve.

Did that and nothing.

If you haven't already done this, I would suggest unplugging every connector I could find in the engine compartment and flushing it with contact cleaner and reconnecting.

That might be the next thing i am going to have to do. Really getting frustrated here.

Why do you suspect the TCU in particular?

Because that's were TPS wires go. At least thats what I think they go to from reading stuff online.

It would be great to know for sure where the C connector grounds to and where it travels in the harness.
Click to expand...
 
Well, you need to chase the ground wire "D", that is your problem.
 
While you've got the ECU unplugged and checking for the ground, how about cleaning the connection at the ECU and harness real well. A buddy of mine had a hard to find issue on his XJ and removed the ECU and tightend up the connectors so they grabbed the pins tighter and his problem was solved.
 
I will do that. I just got access to All Data through a friend. And that's pretty much FSM. Was looking through it and just can't find where that wire D on TPS goes. I think that's my issue for everything.
 
Rushin said:
I will do that. I just got access to All Data through a friend. And that's pretty much FSM. Was looking through it and just can't find where that wire D on TPS goes. I think that's my issue for everything.
Click to expand...

assuming '88 has same colors:

- TPS ground exits sensor as a black wire and runs into dash harness.
- changes color (at a plug) and becomes orange/tan
- enters TCU at pin D3
- TCU is grounded through pin D7 with a black wire
 
so the '88 diagram shows. I'd use pin D3 before I trusted the color, though. I know the TCU is interchangeable between the two, so whatever goes to it will be the ground from the TPS.
 
Ok, so i Did some testing today. I followed the Fsm directions on how to test the wiring. first I tested with ingnition on A and D got 3.9 volts. So next i tested continuity between D1 and A. The voltmeter made a chime.. After that I tested continuity between D and D2 on tcu and got a chime too. So there is no break In the wiring. The fsm saysiif all the test show closed circuit- replace tcm and recheck.

So is my tcm bad? Is there a way to test the tcm?
 
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