Hung in First topic thing again

I recently purchased a 1988 Jeep Cherokee Pioneer .... 4.0, IL6, 4x4, 4 speed auto with NP231 TC, with a transmission shifting problem. I bought it with the intentions of just replacing the trans.
Changed fluid and filter in trans and also replaced the TPS (Snapon scanner told us it was bad). No other codes appear now.
Performed the voltage setting test on TPS and I get 0.80 volts on the “A” and “B” respectively as it states in testing procedures. I know that “A” should be 5 volts.

I have the “Hung in First” problem.

When the TCU is disconnected, I am able to go thru the gears as it has been posted here and other places. (1st - 2nd ....3rd......4th)
So it appears to be a electrical problem thus far.

I have done most of the test found here and other places. Including cleaning the ground connections at the battery to block and block to firewall.

HERE ARE MY RESULTS AT TCU
(Using the info found at:
http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html)
C3 5.82 VOLTS OK
C8 .81 VOLTS OK
C9 .81 VOLTS OK
C10 WORKS CORRECTLY OK
C11 POWER 10.57 VOLTS OK
COMFORT 0 VOLTS OK
C14 13.0 OHMS OK
C15 13.0 OHMS OK
C16 13.0 OHMS OK
D1 5.51 VOLTS OK
D2 .80 OPEN THROTTLE POSITION (SHOULD BE 4.5 VOLTS) NOT OK
.80 CLOSED THROTTLE POSITION ( SHOULD BE 0.5 VOLTS) NOT OK
D3 .8 VOLTS (SHOULD BE 0.1 OR LESS) NOT OK
D14 11.58 VOLTS OK
D16 10.72 VOLTS OK

With the three items marked “NOT OK” on the list ....
Would the TCU be bad in this case?
What would I need to do to find the source of the problems that are not reading correctly?

I do have a NSS problem but it does start most of the time. (Gonna fix it soon)
I am confused with the statement he made on the site (mentioned above):
QUOTE:
"If each pin check falls within the proper spec- ification, you can safely say your TCU is a Transmission Condemned Unit."
Is the a typing error as to .......the falls within is a condemned TCU?

I know this horse has been beat'n to death !!!1 on here but I have not found a problem mentioned as this one.
Any suggestions as to getting headed in the correct direction to fix this would be appreciated.

When I read that article, it is all about troubleshooting a hypothetical problem, and trying to decide if the problem is the tranny, or the TCU. I believe he is saying that if all the measurements fall into spec, the problem in his hypothetical situation, is the tranny

As I re-read your post, it looks like your TPS readings at D2 and D3 are shorted, regardless of TPS position....and D3 is TPS Ground....

looks like the TPS is bad to me... maybe ECOMIKE will have some input for you...

I have not found anywhere that there is a way to test the TPS before it gets installed....Is there a way to test it?

I'm not getting the 5 volts to the TPS to start with looks like......so I can't set it.
Does the wire run from the TCU straight to the TPS....possible short maybe?

The 5 volts comes from the TCU and goes to the TPS

pin D1 on TCU, starts out at as a red wire from TCU, then switches to a grey wire at connector to TPS.

if you have it at D1 but not at the TPS you must have an open circuit...

McQue said:

The 5 volts comes from the TCU and goes to the TPS

pin D1 on TCU, starts out at as a red wire from TCU, then switches to a grey wire at connector to TPS.

if you have it at D1 but not at the TPS you must have an open circuit...

Click to expand...

So in essence...if I was to run a new wire from "D1" at the TCU to the TPS and replace the "grey" wire it would work? Or does it go somewheres else then to the TPS?

And my "D3" is not good either....could I run a new wire there also?????
Does it run to the TPS also from the TCU (changes to the black wire at the TPS)?
I think I need a wiring diagram which shows the path of the wires....
Electrical stuff is not my strong point by any means........:dunno:

OK........I found the TPS diagnostics info .....now to try and understand it.
I will need to check the connections to the ECU also to see where the system fails.

B.RAIDER said:

So in essence...if I was to run a new wire from "D1" at the TCU to the TPS and replace the "grey" wire it would work? Or does it go somewheres else then to the TPS?

And my "D3" is not good either....could I run a new wire there also?????
Does it run to the TPS also from the TCU (changes to the black wire at the TPS)?
I think I need a wiring diagram which shows the path of the wires....
Electrical stuff is not my strong point by any means........:dunno:

OK........I found the TPS diagnostics info .....now to try and understand it.
I will need to check the connections to the ECU also to see where the system fails.

Click to expand...

OK, first off (pun intended) before we can get going here (pun intended) I need to comment on thread titles! I think it's time we held a thread title naming class around here!!!!

It was only out of shear bordom that I bothered to open and peak at this thread! Now let's see if we can get out of first now, LOL.:laugh3:

D at the TPS is the ground wire to the TCU, same as D3 at the TCU, they both need to read less then 1 ohm to a good ground (the negative battery post is the only reliable ground for testing, unless you have verified a secondary ground as good to the negative battery post and decide to use it).

I had to run a new ground wire from D at the TPS harness on mine, I spliced into the harness side of D and ran the splice directly to the negative battery post, that and a new TPS solved my shifting problems. I found it easier to just run a new ground than to try and find the bad spot in the wiring.

C5 and D7 at the TCU are also grounds, or should be! You do not show test results for them? I suggest checking and fixing them if needed.

The wire from D1 to the TPS has a huge voltage drop across it. Easiest fix is to run a new one from D1 at the TCU to the A at the TPS. Then recheck your TPS and TCU readings as those 2, two new wires, one new ground to D at the TPS, and a new wire from D1, at the TCU, to A at the TPS, should fix your problem.

Your voltage drop between D1 at A could be an infamous C-101 bulkhead connector with some bad connections inside, or it could be a broken wire that is just barely still making contact somewhere :bawl: in the harness, or a poor connection at the TCU or the TPS connections, or as McQue said from a short!!! :worship:, which would be a good reason to replace it!!!

The C-101 is just above the brake vacuum booster under the hood.

Your D3 wire is OK!!!! Leave it alone!

D1 goes from red to grey at the TPS
D2 goes from gray-T to blue at the TPS
D3 goes from tan-orange to black at the TPS

for the 1988 year!

I suspect you are going to find out you bought a great deal as a few wires for a fix, is cheap compared to stealership transmission repairs!!!!:scottm:

Oh, and once you get it working you need to read up on the updated TPS calibration, calls for using 83% of the A value at the TPS (TCU side!) for the B value at the TPS at idle, all on the TCU side of the TPS as the proper idle setting for the TPS. That is an updated procedure from the ECU side setting of the TPS to 0.73 volts at idle. Either should work for a new TPS, but both should be checked as either being off is not good.

For more long drawn out details on TPS testing on Renix jeeps, like off the vehicle testing of the TPS, and some other renix horror stories and how I finally fixed them, check out the thread named "RenX Files" here in the OEM forum. Be for warned, it is not a short thread!

Forgive me for starting from scratch electrically and simplified I hope.
You can check this one with a Volt/Ohm meter.
Gray at the TPS and the Red input to the TCU (D1) should both be 5 volts +/- with key "ON"
(although while troubleshooting I found the 5 v supply gets shuts down after a few minutes unless engine is running)
Blue at TPS and D2 at TCU should vary between +/- 5 v and ground with throttle position.
Black at TPS and D3 at TCU should read close to zero volts +/-. (ground)

Was the TPS harness rewired under the hood?

If it helps I can tell you C3 on the TCU is for road speed.
A pulsing voltage from a sensor on the output of your transmission
only with MPH of course. I guess you would have to safely jack up both rear wheels to readily test that.
C16 should have either ground or have voltage (not sure without digging) when in first gear if TCU is working and supplied with 12 volts on D14 and D16 with key on run, D14 always.
The test you showed doesn't say what gear C8, C9,(NSS) was taken in.
If in drive, It seems to be correct with the FSM.
Looks like the Tranny solenoids all check OK -electrically-

TPS wiring sounds most suspect
It looks like D2 and D3 harness connections are reversed at the TPS.

Thanks for the replies.

Now I have a starting point as to where to begin.

I only paid $300.00 for the Jeep and I picked it up at the autoshop where it had been worked on. I paid the shop bill and the owner gave me the title.

ECOMIKE you mentioned the c101 bulkhead connector.....I’m gonna start there first.

The shop had just put on a new brake booster, new master cylinder and checked the brakes. They might have done something there. So being that you mentioned where it is located....that might be the source.

I also believe the shop might have sabotaged the Jeep (owner wouldn’t pay bill ..... maybe). Upon getting the Jeep home I also noticed that the power/comfort fuse in the fuse block was missing (strange). Also the NSS is acting up.

The Jeep is in pretty good shape for a 20 year old vehicle (217,xxx miles). It appears to have never been off roaded much (clean undercarriage).
There are no oil or transmission leaks anywhere underneath ...except for a small valve cover leak.

I replaced the TPS back in December and have only driven it briefly to check the shifting problem.

Found the problem........Shifting problem is no more (for now anyways). I'm one "HAPPY CAMPER" :sunshine: party1:

As I suspected ....I think the Jeep was sabotaged.:nono:
As mentioned earlier I was suspicious when I found the fuse missing. Upon starting to look at the c101 connector we found a red wire that looked like it was freshly cut. As a matter of fact it had another small clean cut next to where it was severed that was partially cut. It was the "red" wire in the harness that goes to the TPS.

Upon testing the connections at the TCU, I found that I had a bad test lead and I was getting different readings each time I did a test and repeated it. New test leads solved that problem.

The owner told me when I bought the Jeep that there was no problems with the shifting until the last repair on the brake booster.

Besides this having the new parts I mentioned replaced, I have since found out that the starter, alternator, plugs, plug wires, distributor cap and components, fuel regulator and all six injectors are new.
So I think I got a pretty good deal.

So as mentioned before....THANKS Ecomike and cygnus58 for your replies they helped me...... as to where to "start" looking for sure.

B.RAIDER said:

Found the problem........Shifting problem is no more (for now anyways). I'm one "HAPPY CAMPER" :sunshine: party1:

As I suspected ....I think the Jeep was sabotaged.:nono:
As mentioned earlier I was suspicious when I found the fuse missing. Upon starting to look at the c101 connector we found a red wire that looked like it was freshly cut. As a matter of fact it had another small clean cut next to where it was severed that was partially cut. It was the "red" wire in the harness that goes to the TPS.

Upon testing the connections at the TCU, I found that I had a bad test lead and I was getting different readings each time I did a test and repeated it. New test leads solved that problem.

The owner told me when I bought the Jeep that there was no problems with the shifting until the last repair on the brake booster.

Besides this having the new parts I mentioned replaced, I have since found out that the starter, alternator, plugs, plug wires, distributor cap and components, fuel regulator and all six injectors are new.
So I think I got a pretty good deal.

So as mentioned before....THANKS Ecomike and cygnus58 for your replies they helped me...... as to where to "start" looking for sure.

Click to expand...

Actually it sounds like you really got taken to the cleaners and paid way too much for it, but I would be happy to help you out and take it off your hands for $400, just feeling generous today, LOL.

What part of Texas????

Ecomike said:

Actually it sounds like you really got taken to the cleaners and paid way too much for it

Click to expand...

:doh: LOL :clap:

Ecomike said:

What part of Texas????

Click to expand...

Right outside of Waco. :wave:

Glad you got it fixed! good info in here -- Call the shop and call them out on it!!!!!!

RyanM said:

Call the shop and call them out on it!!!!!!

Click to expand...

I found the Jeep on Craigslist.
I had thought of emailing the previous owner and telling him what I found, so he would be more cautious about using that particular shop .... but decided against it, because it might seem as if I would be "rubbing it in" that I got it fixed so "cheap".

RyanM said:

good info in here

Click to expand...

There is an enormous wealth of info on this site, if you are willing to take the time and do the search....glad I found it.
To all that make this site great.........THANKS :thumbup:

That is one of the reasons why I don't pay anyone to work on my car (exept alignment).

Being cheap is another.

I thought your meter was a litle funny looking at the NSS voltages. Anyway, for future readers I like to point out that the TPS voltages changed between Renix and HO. Instead of the TPS signal (D2) running 5-volts->0-volts, it changed to running 0->5 volts, same as what the ECM gets.

If it wasn't a dorked up TPS, I was going to suggest unplugging the NSS to eliminate it as a cause and then verify the rear speed sensor was working.