TABBOO

Hope somebody can help me!! My 87 TA 305 TPI keeps throwing a code 22 but only intermittantly. I have checked the wiring & here is what I get: terminals A to C 5.0v. terminal c to battery ground 5.0v. terminal C to battery ground 0.1v with key off & 32.0v. with key on. I am at a loss as to how I can get 32.0v. out of a 12v system but I have checked it 3 times. I cleaned a chassis ground just above the air cleaner but no change was produced. Any help woukd be deeply appreciated. Thanks!!!!

Bens3rdGen

Quote:
here is what I get: terminals A to C 5.0v.
terminal c to battery ground 5.0v. terminal C to battery ground 0.1v with key off & 32.0v

I'm getting confused. When you put the meter between terminal C and battery ground, with the key on, what voltage do you get.
32v or 5v?

TABBOO

This will just go to show I should have reviewed my post before posting!! I get 5.0v from pin A to C. 5.0v from pin C to battery ground. Here is where I had the wrong info listed, I get from pin A (ground pin) 0.1v with ignition off &
32.0v with the ignition on. Sorry for the wrong info no wonder I confused you.

Bens3rdGen

What is you voltage across the battery with the key on only and with the engine on?

TABBOO

I have found a big mistake in my voltage readings. I just got an autoranging meter & instead of 32volts on post A with the key on I am getting .032 volts, I missed that it had autoranged down to Mv. I hope this helps. I will have to get some jumper wires at work to measure volts with the engine running. These are my readings now:

A to C 5.0 volts with ignition on
A to battery ground .032 volts with ignition on
C to battery ground 5.0 volts with ignition on

I hope this helps, I am sorry for wrong info before. I don't know how I even thought I could get 32 volts from a 12 volt system!!!

deadbird

A (blk wire) is the ECM ground.
B (dark blue) is the TPS signal
C (grey) is the 5v reference from the ECM.

Jump your meter from A to B. Your voltage should be o.54v +/- o.o8. Adjust TPS to achieve proper voltage.

Reset codes (disconnect battery for 10ish seconds), take for a short drive and see if it sets another code.

Bens3rdGen

Only way I could figure you could get 32 volts out of a 12v system is if the system was supplying more than 12 volts (batt or alt). I've never heard of that before and I can't imagine it wouldn't toast your ecu before your tps. Glad you figured it out.

Deadbird explained the process well. You can also check that tps puts out around 4v or more with the throttle all the way open. It is suggested that you do this with key one and engine OFF. Otherwise things can get loud and rev limiters get uppity.

Ben

TABBOO

I have already done all the things that deadbird suggested the tps has been evaluated with a scan tool. If I reset the car is OK for about a 20 minute drive but then resets the code. I have noticed thaat just before it sets the code the engine seems to stumble for just a second. Just to update sorry about the 32 volt post it is really .032 volts I just got my first autoranging voltmeter & didn't notice that it had ranged down to Mv. I sure have egg on my face over that one. Sorry again for the bad info, I work swing shift & chaecked it on midnights when I am part braindead!!!
I am concerned that the .032 volt signal on pin C means that I have a problem in the ground wire that is letting voltage leak over into the ground & messing up my tps signal. I would be interested to know what readings anyone without TPS codes has on their car.

Bens3rdGen

When you say evaluated with a scan tool, is that just checking codes. You got code 22 right? Does your scan tool have an o-scope on it? Did you monitor the tps while driving? Their are lots of scan tools with different abilities, which do you have?

Getting confused again, you said...

A to C 5.0 volts with ignition on
A to battery ground .032 volts with ignition on
'C to battery ground 5.0 volts with ignition on'

and now you are saying...
'I am concerned that the .032 volt signal on pin C means that I have a problem in the ground wire'

From pins A to C what voltage do you get and from C to battery ground what voltage do you get. If you get anything other than 5v for either you've got a problem.

TABBOO

The scan tool evaluation was done by a local garage because I don't own a scan tool. He said he checked the operation of the TPS through the whole throttle range,checked the O2 sensor readings. I don't know if he checked it while driving.
A to C I get 5.0 volts
C to ground I get 5.0 volts
A to ground I get .032 volts.
I was told by someone if I get any voltage at all this might indicate a bad ground.
Could it be possible I have a problem with the B wire not always giving the right signal?I hope this helps clarify my problem
Thanks

TABBOO

In my previous post I meant to write that I am concerned about reading any voltage at all on the A pin to ground.
I typed C by mistake. I hope that clarifies the problem.
My 5 volt reference signal checks good A to C & C to ground.
I am concerned that I get any voltage at all from the A (ground wire) to the negative battery terminal.

Bens3rdGen

Maybe you already know this but...
When you measure between A and battery ground you are doing a voltage drop test. You are checking how many volts you are loosing between the Pin A and the battery.

The general rule is .1v per connection with a max of .5v loss total.
.32v is okay, .2v would better but it shouldn't cause the problem your describing. If you want you can put dielectric grease any connections you can find, also take some fine sand paper to the male pins.

The easiest way to check this problem is to drive around with a scan tool on your car and see what the TPS voltage does. Maybe the mechanic did this and the code never came up while he was driving or maybe he didn't test it that way. I don't know if you can call and find out. In any case, you don't have a scan tool.

If it takes 20 mins before it throws the code it might be an intermittent problem. One thing you can try...

Take a paper clip, straighten it as much as possible, then cut it in half. With your TPS hooked up the way it should be, back probe the black and drk blue wires (pin A and B). By back probe I mean stick the paper clip in the back of the connector, it's a little tricky to do with out damaging anything, take your time. Basically you should be able to read the voltage across these pins with everything connected. Next attach some wires to the paper clips with either solder to crimp connectors. The wires should be long enough to reach the drivers seat. I'd put electrical tape around each paper clip and the wire they are probing. Basically you don't want the paper clip moving at all and you DO NOT want them touching. Now if you hook your meter to these wires you should be able to read the voltage of the tps as you drive around. BTW, I'd back probe the connector at the computer if you can, if not the actual TPS is okay. Check what the voltage is when you get the code.

deadbird

No.. when you connect terminal A to the battery ground... you are testing the voltage between the ECM ground and the battery ground. There should be no voltage from ground to ground.
Resistance, yes. Voltage... not really.

If he was testing from term. C to battery ground... yes.

What is the voltage frome term B to A ?

Code 22 will set if the voltage is less than 0.2v (on term B) for over 3+ seconds while the engine is running.

If there is a short in the wiring to B or C, code 22 will set as well.

Bens3rdGen

TABOO said...

"I have already done all the things that deadbird suggested the tps has been evaluated with a scan tool."

This would suggest to me that he has already checked the TPS voltage from pin A to B and it was within the .54 -/+ .08 spec you stated before. This could be intermittent problem.



Dead bird said...

No.. when you connect terminal A to the battery ground... you are testing the voltage between the ECM ground and the battery ground. There should be no voltage from ground to ground.


Actually you are testing the entire ground circuit from the TPS connector through the ecm to the battery. When you measure a from one side of a circuit to the other it's called a voltage drop test. If you have any resistance you will loose voltage, it's part of Ohm's Law. If you'd like I can e-mail you some puplished material on the subject or you also have a good description of how voltage drop tests work in the 'Tech: How to properly wire your electronics ' sticky at the top of this message board.

TABBOO

Sorry for the late reply. I took the car to a computer & wiring specialist & he found a couple bad ECM connector pins in the plug & a frayed TPS wire. He didn't say which one but I suspect it was the ground wire. Anyway $275.00 later the car is fine & the codes have gone away. Again thanks for the help, this one was just way to complicated for me to find.

Bens3rdGen

Glad you got it fixed. Just out of curiosity, do you know if repaired the wiring harness or did he replace it?

TABBOO

He replaced 2 sockets in the plug that plugs into the ECM & repaired one wire out by the TPS under the hood.
So he just repaired what was wrong, the rest of the harness was good.

Bens3rdGen

Did he replace the whole 32pin (?) connector or did he just repair 1 or 2 pins in the connector. I have a harness that needs some connectors repaired and I'm wondering how much it's going to cost.

Ben

TABBOO

He replaced just 2 connectors. The connectors can be replaced individually. Any good auto electrical shop can do it, they will probably charge by the hour. So however long it takes for him to confirm the connectors are bad & to soder the new ones in is what you will pay. Good luck wiring problems are very confusing & as I found they suck trying to pin them down yourself without the right equipment.
It sure is good to be out & running again too bad it will be time to put the TA away next month till spring.