slow_evo

I've been a lurker on this forum for several years and decided to create an account. My vehicle is a 98 XJ Classic 4 door with a RC 4.5 lift and 33s, 145,000 mi. Other than that, stock.

Last week I got a CEL, code was p0107 -- MAP sensor. After replacing that and clearing the code, the CEL did not return. Drove it for about 30 min and the TC was locking up fine in OD. Turned it off and returned to drive it about 2 hours later, CEL returned (I thought it was the p0107 code), but after pulling it, it was in fact the p0700 code (no other codes along with this one).

Went on a test drive and it is shifting perfectly, except for no TC lockup in OD. The only trans related service I've done recently was a drain and refill about 6 months ago.

Did some research on p0700 and found various threads to check the inside fuses near the passenger kick panel, clean/adjust the NSS, check the TC lockup solenoid. Most of the time, p0700 is accompanied with other trans related codes (usually the solenoids or speed sensors, but not in my case).

My questions are:

1. I believe you can check the ohms on the solenoids without dropping the trans pan, but where/how do you do this? I think I need to pull the harness at the TCU, but I can't locate it. I know it should be under the passenger side dash, but all I found so far is a bright green connector behind the glove box. Is that it? It has a large letter "D" on the connector/harness.

2. Could the NSS actually cause this? My reverse lights have been spotty since I purchased the vehicle in 2011, but never had any start problems etc. I can go ahead and clean this, but I'm not sure this is where the problem is.

3. I checked all the fuses inside the cab and they are all good. I'm wondering if the brake switch is stuck ON so the TC never locks up, but I don't know where this is located. Any one know?

4. I also checked the TPS and this appears to be working correctly.

Any other ideas/questions, please let me know.

mlepesant

Hi there. please start by searching the following posts:
"0740 trans code dilemna", you will find some testing procedures and a picture (post 4)of the connector in the engine bay from which you can test the solenoids.
"P0740 trans code + test results": for testing procedures of thr TCM, brake lamp switch, solenoid circuit, Tps.
"procedure needed to check P0740 + P0743": for procedure to test solenoids in engine bay (post 10)

You will see that I am in about all of those posts, asking questions... I still haven't resolved my P0740 for well over a year now. i am dropping the pan this week to replace the plastic connectors in the wiring harness (as well as the solenoids). For now I keep clearing the codes, but my mileage is suffering.
Anyway, i hope this will help somehow.
Marc

mlepesant

The TCU is located under the driver side dash, right side against the transmission well or whatever that is called. grey rectangular box with a rectangular connector with about 20 wires or so.
The brake lamp switch is behind the brake pedal.
There are several pictures/drawings around the forum. Sorry but i don't have them handy.

CCKen

Your TCM is located on the driver's side, under the dash, to the right of the steering column. You have to remove the trim panel and knee blocker from around the bottom of the steering column to get at it. It's a small silver box, held on with two fasteners.

Go to this thread, post #5. It shows the TCM connector pin-out and functions chart and procedures for testing the TCM circuits. The post is unrelated to TC lock-up but at least it has the charts.

https://www.cherokeeforum.com/f2/tra...-issue-203640/

Does the CEL come on as soon as you start the Jeep or does it come on when you start driving it.

Generally, if it's an electrical problem, the CEL will come on immediately and with a mechanical problem it will put the light on when an electrical signal is sent to a solenoid (for example) and the solenoid doesn't respond.

CCKen

https://www.cherokeeforum.com/f2/tro...143006/index2/

Go to this thread and down to post #16. There's a discussion about the Brake Lamp Switch (TC Lock-Up)

slow_evo

mlepesant, thanks for the tips, I'll take a look at those threads.

CCKen, I will also check out the thread referenced here for more info. The CEL is on as soon as I turn the key to "RUN" (not START). In other words, I disconnect the battery, hold the brake pedal for 10 sec to desipate remaining charge and wait 30 min until I reconnect the battery. I get back into the cab and turn the key to RUN and the code is there. I scanned it too without every turning on the engine after reconnecting the battery and the p0700 code is still there.

I will check the threads referenced and continue with troubleshooting. I'll report back once I have something. Thanks guys!

superbee1970440

P0700 is just a generic transmission code. You need a scanner with the ability to read transmission codes. This should give you a much better idea of what is going on.

Sam

slow_evo

Alright, I checked all three trans solenoids from the engine compartment and they measured between 12.1 - 12.3 ohms.

I'm in the process of checking the TCM using the following thread:

https://www.cherokeeforum.com/f2/p07...esults-197883/

However, my test leads are not narrow enough to fit inside the TCM connectors. With that said, is the only other possible culprit the brake switch? If so, would I also be throwing "P0703 Torque Converter/Brake Switch B Circuit Malfunction" or could the switch be bad and the code wouldn't necessarily be there?

Is another possiblity be the TCM itself? I wouldn't think it would be this since everything else regarding the trans works fine.

Sam, I read in another thread that this is almost useless since the TCM will report a very generic code and I would need to troubleshoot most of the system anyways.

CCKen

Use safety pins to probe the TCM connector pin cavities.

Open this thread and scroll down to post #53 for a discussion on the use of safety pins.

https://www.cherokeeforum.com/f2/gre...e-6558/index4/

Use the pin-out chart and test procedures in this thread, not the other one:

https://www.cherokeeforum.com/f2/transmission-shifting-out-1st-issue-203640/

These test procedures do not include a test of the Brake Lamp Switch. I've yet to figure out a practical way of doing it through the TCM connector. The only real way to check it is to remove the Switch and bench test it, but since you'll have it out - replace it. Only $15 +/-. Since you have P0703 I would suspect the Switch anyway.

slow_evo

Thanks, Ken. I'll reference the other thread. To clarify, I do not have p0703, only p0700. Is it possible to have a bad brake switch but not throw p0703, as in my case?

If it's not the TC lockup solenoid, is the only other possibility left the brake switch? I will still go through the TCM pinout troubleshooting guide you posted nonetheless. Thanks!

CCKen

The 2000 XJ Diagnostics Manual doesn't even list 703 anymore. My '99 DTC list has it though, but with no diagnostics.

The Brake Lamp Switch is a trouble maker, and is cheap to replace so I would start there. But do the solenoids test from the TCM connector to make sure the wiring from the TCM down to the connector by the dipstick is okay.

Also, make sure you do the voltage check on the TPS. It's odd how the TPS can screw things up with shifting.

slow_evo

Alright, quick update here:

I went ahead and installed the new brake light switch while the battery was disconnected. Reconnected the battery and turned the key to ON (engine not running). My CEL was illuminated so I pulled the code(s). Now I am receiving:

p0700

p0705

The p0705 points to the NSS. I will go ahead and take this apart and clean it. I find it odd that I all of a sudden I'm throwing the p0705 code, but I suppose that's how these things can go.

Once I clean the NSS and verify the p0705 is gone, but p0700 remains, I'll continue with the TCM troubleshooting.

CCKen

If you do the voltage checks of the NSS (TRS) on those check procedures, it may reveal your problem.

CCKen

705 can be caused by many problems.

Here's a list of possible causes:

PCM PARK/NEUTRAL DTC’S PRESENT
INTERMITTENT WIRING AND/OR CONNECTORS
FUSED IGNITION SWITCH OUTPUT OPEN OR HIGH RESISTANCE
TRS 1-2 SENSE CIRCUIT OPEN
TRS 3 SENSE CIRCUIT OPEN
TRS OVERDRIVE SENSE CIRCUIT OPEN
TRS REVERSE SENSE CIRCUIT OPEN
TRS 1-2 SENSE CIRCUIT SHORTED TO GROUND
TRS 3 SENSE CIRCUIT SHORTED TO GROUND
TRS OVERDRIVE SENSE CIRCUIT SHORTED TO GROUND
TRS REVERSE SENSE CIRCUIT SHORTED TO GROUND
TRS 1-2 SENSE CIRCUIT SHORTED TO VOLTAGE
TRS 3 SENSE CIRCUIT SHORTED TO VOLTAGE
TRS OVERDRIVE SENSE CIRCUIT SHORTED TO VOLTAGE
TRS REVERSE SENSE CIRCUIT SHORTED TO VOLTAGE
TRANS RANGE SENSOR-SENSE CIRCUIT
TCM-TRS SENSE CIRCUIT INPUTS

slow_evo

Thanks for the info, I'll check it out.