Engine and transmission problem codes P0700 and P0740

Tiny
SAM TODORA
  • MEMBER
  • 1998 JEEP CHEROKEE
  • 4.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 202,000 MILES
A few months ago I started having transmission problems, I took it to a transmission shop in the area with a lot of good reviews online and had it rebuilt. They messed up the rebuild and it was slipping so I took it back as soon as I could (I was away at college a lot this past year). The engine has also had a strange sort of murmur for awhile, but it was not really effecting the driving and it only happened at idle so I never thought much of it; it is an old Cherokee. I got back home for summer break and my dad told me that, after the car heats up, he noticed the murmur would happen and now the car kind of cuts out when accelerating. I noticed that it also sort of cuts in and out of acceleration while driving between 55 and 65 mph. The only codes that come up with the check engine light are P0700 and P0740. Having had transmission issues, I was familiar with these codes so I took it back to the transmission shop where they told me that the engine was misfiring which would cause the torque converter to cease to lock up which was why I was getting those two codes and that I would need to fix the engine and not the transmission. The problem is, there are no codes indicating misfires, bad fuel injectors, bad o2 sensors, etc, so I am having a lot of trouble diagnosing the problem. The coolant is new and full, and I replaced the idle air control valve, but that did nothing. Any thoughts?
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Wednesday, May 25th, 2016 AT 2:01 PM

6 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
The IAC is only used at an idle to allow air into the intake system, allowing the engine to run at idle. As far as the sound, was there anything which changed it? Next, the codes are related to the TCM. The TCM on your vehicle is located on the driver's side under the dash. It is a plastic box about 4 inches x 4 inches. Make sure all connections are clean and tight. The only other thing I can think of that is remotely related was I did have a similar issue with a 98 years back. Same driveability issues you described. It ended up being the crank position sensor that was sending, but that was the only one I ever had. Keep in mind, the TCM is controlled by several things. The throttle position sensor, brake light switch, speed sensor, and the transmission range sensor. Information from these sensors indicate when the transmission should shift and OD lock up. If any of the information sent to the TCM is wrong, crazy things start to happen. Since you have no misfire codes, I am leaning toward an issue with the TPS (throttle position sensor) which in my mind is the only thing that would cause the drivability issues you mentioned. If you have a live / real time scanner, check to see how the TPS is reacting under different circumstances. It could be the issue.
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Wednesday, May 25th, 2016 AT 8:20 PM
Tiny
SAM TODORA
  • MEMBER
Nothing has changed the sound, I should have been more specific than "murmur" it's either a slight drop or a slight rise in the RPM's usually a drop. Thanks for the help, I didn't think about the TPS, I'll check it tomorrow.
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Wednesday, May 25th, 2016 AT 9:05 PM
Tiny
HMAC300
  • EXPERT
Just to add, because it's a 4.0L check engine harness at rear of head the harness will rub through at stud on cylinder head and cause all sorts of problems. If it is fix the wiring and try to reroute the harness if possible.
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Thursday, May 26th, 2016 AT 5:41 AM
Tiny
SAM TODORA
  • MEMBER
Thanks, I'll check that too. Gotta love mopar electronics! (Sarcasm)
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Thursday, May 26th, 2016 AT 11:19 AM
Tiny
SAM TODORA
  • MEMBER
I checked the wiring and everything was fine and I replaced all the sensors on the throttle body with sensors from my dad's wrangler which has the exact same drivetrain. This did nothing to change the problem, so it's not any of the sensors related to the throttle body. Any other thoughts? I've read some things about the coolant temperature sensor. Could it be that? How do I test it?
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Thursday, May 26th, 2016 AT 8:14 PM
Tiny
HMAC300
  • EXPERT
Pic shows probable causes misfire is one of them have a local pro freeze frame to see if anything is making it misfire. That will be your cheapest way out with checking and replacing all kinds of parts to find it only to not find it.
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Friday, May 27th, 2016 AT 6:30 AM

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