Ken Huey

1999 Cherokee Sport 4.0L, AW4 Automatic Transmission, Selec-Trac 4WD...Engine starts & runs normally but vehicle does not move (at all)...Only OBDII Trouble Code is P0751: "Shift Solenoid A CKT performance or Stuck Off"...I Understand the AW4 trans is electronically controlled with 3 solenoids located on the Valve Body...I understand that Solenoid #3 "Shift Solenoid" controls the Lock Up Torque Converter...I understand that each solenoid should test between 11 -15 OHMS; if good...I understand the process necessary to change one or all of the solenoids...The information I have not been able to locate is a way to check the solenoids electrically without going into the transmission...Please remember the 1999 Cherokee Sport does not have a "stand alone" TCU (Transmission Control Unit) - In 1999 the TCU was integrated into the PCM (Powertrain Control Module)...I have yet to locate diagrams for the 3 PCM Connectors; C-1 Black, C-2 White, C-3 Grey Connector, to determine if the solenoids can be tested with a OHM Meter in a similar manner to testing at the pre-1999 TCU Connector at C14, C15, & C16...Also, would appreciate any information/suggestions to trouble shoot my vehicle symptoms and Trouble Code P0751...Thanking all in advance!

Well being a "Newbie" I guess I had to learn that you should not/can not believe everything you read in a Forum or on a Web Site...The information stating that the Cherokee Sport, as described above, does not have a "stand alone" TCU is incorrect... It does in fact have a TCM (Transmission Control Module) located under the dash above and to the right of the gas pedel... Attachment #1 is the TCM removed from my vehicle (two 8mm bolts)... Attachment #2 is a picture of the TCM "Pins"... The 3 pins in the upper right corner are the 3 that connect to the 3 transmission solenoids... Attachment #3 has two connector diagrams... The first is the TCM Connector...CAV 11, 12, & 13 are the 3 that should test 11-15 OHMS if each solenoid is good... The second connector is located at the transmission for the Transmission Control Assembly & testing could be done here as well... Why crawl under the vehicle if it's not necessary...My 3 transmission solenoids checked good at 11 OHMS each... On to more trouble shooting... Would appreciate any help or suggestions.

blue01xj

We have the same code and trans will not go into overdrive. Will use this information to test mine before I rebuild/clean my NSS.

Thanks for the useful information.

CCKen

Do a voltage check from the TPS to the TCM.

Refer to your pinout.

Turn key to RUN.

Using a voltmeter, (+) probe to pin cavity 17, (-) to 24. You should see the TPS idle voltage. Depress gas pedal, now you should see TPS WOT voltage.

~~~~

Do a resistance check of the Input and Output Speed Sensors.

Remove the battery negative post connector.

Read resistance between pin cavities 1 and 2, then 3 and 4. Each speed sensor should read about 625-650 Ohms.

blue01xj

Need help PO700/PO751 trouble codes.


1998 4.0L AW4 NP242 Limited
Replaced all Solenoids and the old ones ohm ed out at 13-14
Swapped TCU's with the one in my 2000 and still will not shift.
Adjusted the TV cable

About out of ideas other than the torque converter it self and really dont wanna pull the tranny/tcase.

When I manually shift in 1-2 it will shift into 2 at 4K+, then I manually put it in 3rd and it shifts, but when I run 3rd out some and shift into OD the rpm needle bounces like it wants to shift but does not go into 4th or OD

Any ideas? Thanks in advance

CCKen

Hve you tried checking the resistance of the new solenoids from the TCM connector?

Disconnect the TCM and try manually shifting. If that works okay you still have an electrical problem. If it doesn't shift properly, you have a transmission problem.

Is you transmission fluid level at full (when at operting temp)? Does your trans fluid look black-ish and/or smell burnt?

blue01xj

CCKen, I check the resistance of them all (new and old) out of the transmission.
I disconnected the TCM and manually shifted with same results.
Was at full
Trans fluid is red but was just changed when the solenoids and filter was done.
Old fluid was dark but not sure how old it was.

blue01xj

Tried using 24 as ground, and ohm ed 11,12,13 to get no reading.
Gonna try to find the harness diagram to see where it goes in jeep for bad connectors or bad wires.
Thanks for the help so far.

CCKen

Are you sure you installed the correct solenoids and if they are, are they installed properly?

blue01xj

Yes (before Fireman was a mechanic and also worked on hospital equipment) pulled them from my 01 Jeep XJ in known working condition and yes installed correctly as its One plug and one bolt per each one.

Also went back in a second time and swapped the 1-2 solenoid to the OD solenoid

If I test the black 8 wire plug at the fire wall on pin 2,3,4 I need to ohm the male end going to the tranny, correct.

CCKen

Not sure about the male end, but it would be the connector for the harness going down to the transmission.

Have you verified that the TCM ground (pin Cav 24) at the ignition coil studs (G101) is free from corrosion?

blue01xj

Tested the 8 pin plug at the fire wall.

Pin 2, 3, 4 all read 13.5-13.8 ohms

With that information I assume between the 8 pin plug at the fire wall and the TCU plug under the dash I have a bad wire.

I have not verified TCM ground (pin Cav 24) at the ignition coil studs (G101). Will look that up and see if I can find it. This 98 has the dizzy and all 9 other XJ's I have owned all had the coil packs.

Thanks again, feel that Im getting somewhere.

blue01xj

found them on the is thread
https://www.cherokeeforum.com/f2/wei...roblem-188798/

Going out to check them now.

blue01xj

I Think the ground is fixed now. Im able to read pin 11,12,13 and all within spec.
When I leave the fire station tomorrow morning I will road test it and see...............

Stand by tomorrow for details




CCKen Thanks for all the help

CCKen

Cool.

I look for your report.

blue01xj

Well road tested it and still no over drive. Does the same and tried manually going down to 3rd and back to D with no change in rpms other than a flicker of the needle.

Guess now I should swap TCU's again and road test to rule out TCU again?
I have another 98 with 69K miles sitting here that I can swap any part from if need be.