2000 Jeep Cherokee - Trans Code P0470

[spencersauto]

We recently replaced transmission with a jasper. When vehicle came in SCANNED FOR CODES AND FOUND P0740 TCC SOLENOID FUNCTIONAL FAULT, AND P0751 SHIFT SOLENOID A (1-2/3-4) FUNCTIONAL FAULT. Vehicle was slipping and had no reverse. Code P0740 had been setting for months. After replacing transmission code P0740 has returned.No problems with transmission for the last two weeks. This is a postal vehicle and seems to be a common problem among postal vehicles, but have been unable to locate problem. Code sets after driving 15-30 minutes with stopping and going. Customer called this morning and states transmission is starting to hesitate in reverse.

[ricmorin]

Given the symptoms, I'm inclined to think the transmission may be failing. I'd make sure that the circuit for the TCC is complete and functioning. 740 sets when the PCM energizes the TCC and the input and output RPM's do not match. If there was an open circuit or PCM fault, it would set. How does the fluid look? Any other codes? It will also set if the TCC sticks on when de-energized. Can you feel TCC on/off while driving?

[spencersauto]

A little history--This is a rural mail jeep with approx 150k.This code has been present in the vehicle for the past two years with no driveability concerns or trans problems. The transmission finally let go. It lost reverse gear. We just installed a Jasper transmission two weeks ago. Test drove it 25 miles and all was well. The customer returned two days later with the same old code--P0740. TCC is engaging and disengaging with a noticeable RPM drop. You can press the brake pedal and feel it disengage and watch it engage on the scanner. The only problem I can see it that when the TCC applies it loses the input speed sensor. It drops to 0. When you slow down to around 20 mph, the sensor starts reading correctly. I've swapped the input and output sensors with no change. Ive found numerous posts on the internet about this problem with mail jeeps but no fixes.

[ricmorin]

Well there's your problem! LOL

The reason the 740 sets is because the speeds are not matching. Now to find why the input speed sensor goes out. Hmmmmm. Have you scoped the waveform to see what actually happens? This is a regular Cherokee, not a Grand? Which engine? 2 or 4 wd? I'm surprised it hasn't set an input speed sensor code.

[ricmorin]

A thought is the lockup solenoid wire is shorted to one of the speed sensor wires. They are not next to each other in the electrical connector( I'd look carefully at the connector anyways) but they could be shorted or pinched somewhere in the harness. By scoping the ISS you may have a better understanding of what's happening to the signal. If it goes 12v on the ISS, you may have a short.

[Tim Martin]

While I can agree with the helpful ideas given so far, you need to be calling Jasper about this one, especially if it is still under warranty, i'd think. Even if it is not a fault of theres, they will be able to help you with the fix. So far, I have had good success with their tech help.

[steven kiser]

going way out here in memory land here. i had a few with bad t.p.s's as well as 02 wire shorted that have caused this issue. don't know why but there have been jeeps is my family for years and i've seen it all. also isn't this the year that the pcm's failed and would cause all sorts of no start and transmission issues? i also agree with calling jasper and starting a claim.