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'99 Grand Cherokee Limited - No OD, P0700

3K views 12 replies 5 participants last post by  CC99 
#1 ·
Hi guys,

Fixed a number of things after reading this forum - great bunch of experts!

Now I have a transmission issue with my 4.7/45RFE, 4-wheel jeep. The OD doesn't engage, although the dash light works, just stays in 3rd gear at 60mph. It was also shifting very roughly, and late into 3rd gear. I was getting code P0720.

After reading many posts about this I replaced both speed sensors - was cheap & easy enough. It now shifts pretty smoothly through the gears, but still no OD engagement. Now I get code P0700.

From what I read I'll need a shop to read the next level codes. I only paid $1,200 for this jeep and it's in pretty good shape for 145K miles. Is there any suggestions as to what else I could do? Fluid level is good and looks clean.

Thanks for all the help you guys gave me so far!
 
#2 ·
Just went through this with my wj. Could be a magnitude of things. Find the best tranny shop and they will help. Could be brake light switch, shift solenoid, speed sensor, out adjustment tv cable or the torque converter. Use the search feature they're it's allot of stories with this issue with twice as many fixes

Sent from my LGL44VL using Tapatalk
 
#3 ·
You won't necessarily need a shop to read the code in the TCM. My ~$100 harbor freight reader will do it, as should any parts store reader. Diagnose from there.

BTW - You don't have a TV cable as mentioned above.
 
#6 ·
Thanks for the info guys.

I actually ordered a bluetooth OBDLink (for Android) which will arrive today. I've always wanted one of these anyway and could have used it a number of times. I think it will read all the codes. Hoping that will help narrow it down.

I am still going through many, many posts trying to correlate my issue to possible solutions.

Speed Sensors - already replaced. Seemed to improved shift from 2 to 3.
NSS - think it's ok, backup lights work, starts in park and neutral.
Brake switch - works fine
TPS - idle and startup RPMs seem good, not sure how to test. Is there a way?
TCM - fuses good - haven't tested ground yet, going to try and do that today.

I am going to have the fluid and filter changed and at that time see if there's debris or signs of internal issues. I'll have a local shop do this. Can't do this due to recent back surgery - can't shimmy on my back under the jeep.

I actually sold this jeep to someone 4 years ago with 117K on it and it had impeccable service and zero issues. I just bought it back after I sold a F250 SuperDuty that I no longer need. The jeep was abused by the son and very few service records were kept. It's like "back to the future" and I'm hoping to get the old girl in shape as a second car and to pull my boat a short 2 miles to and from the local boat ramp.

I immediately remembered why I loved this jeep so much and have fixed all the issues, with your help, except for this.
 
#7 ·
I got the new OBDLink scanner - great little device, easy as pie to use.

I see code P0731 - Gear 1 Incorrect Ratio.

From another post:

P0731 JEEP Description
This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows:

Torque converter slip ratio = A x C/B

A: Output shaft revolution signal from revolution sensor
B: Engine speed signal from Engine Control Module (ECM)
C: Gear ratio determined as gear position which TCM supposes

If the actual gear position is higher than the position (1st) supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.


Possible causes
- Low transmission fluid level
- Dirty transmission fluid
- Shift solenoids
- Transmission mechanical problems
- Transmission hydraulic control circuit

I cleared the codes, drove around, and the P0731 came back (dashboard code shows P0700)

I don't think I am in limp mode, but I do now notice weird behavior in gears 1 & 2. From a cold start if I put the shifter into 1st gear and take off it will shift (clunck) to 2nd, then when I shift to 2nd nothing, then when I shift to 3rd it goes into 3rd. Never goes to 4th, runs @ 3K rpm at 60 mph. Then if I stop and take off I believe it's starting in 2nd gear. I drive with a very light foot so didn't notice it wasn't starting off in 1st gear, I guess.

Originally I was getting code P0720 (on the dash), but didn't yet have a scan tool, so not sure if the P0731 was coming up or not. Replacing both speed sensors didn't help the no OD issue, but seemed to help the shift from 2 to 3.

I have read almost every post which mentions P0731 and nothing apparent yet, except most of the time code P0731 is coming along with several other code, not just this one alone?

I guess the next step is to have the fluid and filter changed.

Any other ideas? Thanks!
 
#9 ·
Quick question:
I originally got the P0720 code on the dashboard, this was before I had the OBDLink scanner. After replacing an apparently bad output sensor that's gone, but now I get Code P0700 on the dashboard, and P0731 from the scanner.
Unfortunately, after the sensor replacement I reset the CEL with a battery disconnect.

If the P0731 code was being produced before the sensor replacement shouldn't I have seen a P0700 code on the dashboard in the beginning, in addition to the P0720 I did see? Seems odd if the P0731 didn't happen until the sensors were replaced.
 
#10 ·
Problem Solved!

It turned out that the wiring harness to the input or low speed sensor had a bad connection. After cleaning it and reconnecting, the P0731 code went away. I did this lying on my back under the jeep without jack stands so it was quite difficult to work with the harness connections.

I then had the fluid and filters changed - everything looked great and there was no signs of debris or damage. Now the transmission shifts as smoothly as new and I'm back in business.

Just wanted to close the loop so others might benefit from the experience.
 
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