Trans won't up shift.

[Ecomike]

Thanks Ecomike! I will run the grounds. Did you run one to both sides of your TPS?

No. I should have and someday I wiil, I only fixed the side that had a poor ground, the TCU side. The two sides of the TPS have different ground wires. If you splice them together, and then add a single extra ground to the battery, it should help with old ground wiring problems.

 

[lawsoncl]

I've found a number of crappy ground connections hiding in the Renix wiring harness. The one in the main harness on the firewall right behind the dipstick had a bunch of ground wires just crimped together without a ring or anything.

 

[btam13]

I've found a number of crappy ground connections hiding in the Renix wiring harness. The one in the main harness on the firewall right behind the dipstick had a bunch of ground wires just crimped together without a ring or anything.

You talking about the bundle of grounds coming out of the harness on the passenger side and attaching to the stud on the block about halfway down and just to the rear of the oil filter? If so, yeh, that one looked like crap on mine. Burnt covering, exposed wire strands, melted insulation on the battery negative cable that mounts there also. I cleaned them up, but I really need to replace the negative battery cable and put new ends on the ground wires coming out of the harness.

 

[btam13]

Ok, I installed the new TPS after cleaning the ground at the passenger side block and the one on the head on the drivers side back corner. Adjusted the TPS to .82 volts between the C and B wires on the ECU pigtail of the TPS even though I originally thought that it was suppose to be set while reading the output voltage of the TCU pigtail but took a chance on doing it the other way when I figured out that the TCU pigtail doesn't have a C pin. Took it out for a test drive. Results, trans shifts pretty good now through all gears at about 2500 to 3000 RPMs at WOT. Idle is a too low for my liking though. About 450 RPMs at Idle in park and 350 at idle in drive. Oh, and it died on me once while pulling into a parking lot but started back up fine. Rechecked the TPS adjustment. Still .82 volts. DID NOT install a ground wire from the TPS to the negative post on the battery though. I wasn't sure whether to splice it in on the ECU or TCU pigtail or both. Or whether to splice it in on the TPS side of either connector or on the harness side of the connector. I really need to learn more about using the multimeter I bought today also. I really want to be able to check the resistance in my grounds. Over all, I think I am back to where I was before the trans stopped shifting automatically. Any thoughts on the low idle or if I did anything wrong?

Ecomike, what do you think of this? I originally adjusted the new TPS's output voltage to .82 volts using the ECU pigtail of the TPS as it seemed you suggested, but then I read that this was an obsolete method and that it should be adjusted off of the TCU pigtail. I readjusted it using the TCU pigtail and now have it set at 82% of the input voltage on the TCU pigtail. The strange thing is that after doing this, I rechecked what the output voltage was on the ECU pigtail and found it to be .69 volts. A bit under .82 I would think! The jeep does seem like it has better torque now though and it seems to run a bit smoother. Shifts still seem as firm as I believe they should be. Here are the current readings that the TPS is set at.

ECU Input voltage 4.88
Output voltage .69

TCU Input voltage 4.68
Output voltage 3.87 3.87 divided by 4.68 = .826
What do you think?????

 

[89CherokeePioneer]

After replacing the CPS I'm back.

It did shift out of first, but at 4000RPM and very violently.

 

[btam13]

Wow! Cam position sensor went out while testing what it would do if you try to start and run it with the TPS unplugged. That sucks!

 

[btam13]

Ecomike, what do you think of this? I originally adjusted the new TPS's output voltage to .82 volts using the ECU pigtail of the TPS as it seemed you suggested, but then I read that this was an obsolete method and that it should be adjusted off of the TCU pigtail. I readjusted it using the TCU pigtail and now have it set at 82% of the input voltage on the TCU pigtail. The strange thing is that after doing this, I rechecked what the output voltage was on the ECU pigtail and found it to be .69 volts. A bit under .82 I would think! The jeep does seem like it has better torque now though and it seems to run a bit smoother. Shifts still seem as firm as I believe they should be. Here are the current readings that the TPS is set at.

These are the voltages read at the TPS pigtails. ECU side and TCU side.

ECU Input voltage 4.88
Output voltage .69

TCU Input voltage 4.68
Output voltage 3.87 3.87 divided by 4.68 = .826
What do you think?????

 

[89CherokeePioneer]

I wish it were the Cam sensor. That would have been almost pleasant. It was the crankshaft position sensor on the bellhousing. Quite difficult to get at.

Good luck with your TPS adjustments. I haven't had to mess with it yet.

 

[btam13]

Glad you found the problem 89CherokeePioneer!

These are the voltages read at the TPS pigtails. ECU side and TCU side.

ECU Input voltage 4.88
Output voltage .69

TCU Input voltage 4.68
Output voltage 3.87 3.87 divided by 4.68 = .826 or 82% of input voltage.

What does anyone think about these readings?????

The output voltage for the ECU pigtail is lower than recommended in order to bring the output voltage for the TCU pigtail into recommended spec.

 

[Ecomike]

Ecomike, what do you think of this? I originally adjusted the new TPS's output voltage to .82 volts using the ECU pigtail of the TPS as it seemed you suggested, but then I read that this was an obsolete method and that it should be adjusted off of the TCU pigtail. I readjusted it using the TCU pigtail and now have it set at 82% of the input voltage on the TCU pigtail. The strange thing is that after doing this, I rechecked what the output voltage was on the ECU pigtail and found it to be .69 volts. A bit under .82 I would think! The jeep does seem like it has better torque now though and it seems to run a bit smoother. Shifts still seem as firm as I believe they should be. Here are the current readings that the TPS is set at.

ECU Input voltage 4.88
Output voltage .69

TCU Input voltage 4.68
Output voltage 3.87 3.87 divided by 4.68 = .826
What do you think?????

Actually it is 83% not 82%, and you have 83% so you are good to go.

Next thing you should add to your someday to do list, is to track down the power losses (bad connections) between the ECU 5 volts, the TCU 5 volts and the TPS sensor. You are loosing a good bit between the TCU and the TPS. But make sure the TCU is puting out 5 volts first, before heading out on a wild goose chase. The ECU is not bad (4.88 volts).

 

[btam13]

So, why do some think that it is so important to have the ECU output voltage at .81 volts if you can't even get it there and still keep the TCU output voltage in spec? I know I saw somewhere in your thread Renx Files that someone stated that they have never seen a TCU put out a full 5 volts to the TPS and that most put out 4.6 to 4.8 volts. I would like to see it improve though. Do you think adding the ground patches to the harness side of the ECU and TCU pigtails on the TPS would help bring the input voltage up at all? I'm not sure if it would have that effect on them.

 

[Ecomike]

So, why do some think that it is so important to have the ECU output voltage at .81 volts if you can't even get it there and still keep the TCU output voltage in spec? I know I saw somewhere in your thread Renx Files that someone stated that they have never seen a TCU put out a full 5 volts to the TPS and that most put out 4.6 to 4.8 volts. I would like to see it improve though. Do you think adding the ground patches to the harness side of the ECU and TCU pigtails on the TPS would help bring the input voltage up at all? I'm not sure if it would have that effect on them.

IIRC the 87 FSM said 0.82 volts (or 0.80) on ECU side, the 88 FSM said 0.83 volts, and 89 or 90 said to use 83% of input voltage on the TCU side.

IIRC I have very close to 5 volts on both sides of mine, 87. And my ECU side is about 0.82 volts, even though I set it on the TCU side at 83%.

Seems the 83% is more important than an absolute voltage! Also, it should read about 17% at WOT on the TCU side.

The manual tranny guys must calibrate on the ECU side, as they have no TCU!

No improved grounds will not change the input voltage. Cleaning up dirty 5 volt signal input wire connectors between the ECU/TCU and the TPS will.

 

[btam13]

Thanks Ecomike! You have been a great help. As well as everyone else that gave me their perspective. I guess I will just plug away at trying to improve the input volts on both as I go along. It is running pretty good now though. I disconnected the battery last night for an hour and then re connected it. The TCU should be relearning it's sensor inputs now and hopefully it will ease out of the low idle issue the jeep is experiencing now. Has good idle at cold start. 850 in park, 650 in drive at idle. But when it warms up the idle drops to about 350 in drive, 450 in park. I will see if that will sort itself out and hit the leaking oil filter adapter next. Then on to replacing the wheel ujoints, passenger side is completely shot. Clunks going down the road. Then on to find the grating noise coming from the back end. The sound is like when a joint or something that is binding up pops free but still grates on each respective part as they turn. Any ideas what that might be?

 

[btam13]

Well, I just noticed something strange. Since I replaced the TPS and got it dialed in right, I haven't heard the grating or popping noice that I had been hearing in the rear end. Strange!