06 Jeep Grand Cherokee 5.7L 545RFE

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rc195840
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06 Jeep Grand Cherokee 5.7L 545RFE

Post by rc195840 » Mon Jul 10, 2017 12:28 pm

I have a problem with an 06 Grand Cherokee with 5.7L Hemi with a 545RFE transmission. When the transmission reaches 135 degrees on scanner the cooling fans turn on wide open due to code P0218 (Transmission Over Temp.) being set. Once cycling the key off then on normal operation and transmission temp resumes. This does not happen constantly only intermittently. Using a thermal imager it has been confirmed that the transmission is running at normal temperature. Observed intermittent voltage using a scan tool on transmission temperature sensor after reaching 135 degrees but not before. Radiator, Transmission Cooler, two Solenoid Bodies, PCM, and both transmission filters have all been replaced. Checked wiring from PCM to Transmission and found no obvious faults. Customer had taken this vehicle in to two dealerships before bringing it to my shop. Radiator & transmission cooler were replaced by first dealership, solenoid body was replaced at the second dealership. When preforming my diagnostic on this transmission, temp when the vehicle was started was 70 degrees voltage was about 2.5 volts. As temp goes up voltage drops as it should. It does this smoothly down to about 1.0 volt at 134 degrees. At 135 degrees the voltage rises to 3.5 volts and then begins to decline as temp goes up. Every time I have gotten this to act up it has been when this voltage transition takes place on the scanner at 135 degrees transmission temp. Sometimes this take place with no issues, but sometimes transmission temp will jump to 288 degrees on scanner, set code p0218 and turn both cooling fans on. I have gotten this to happen without vehicle moving just sitting in bay idling. Checking actual temp with thermal imager on cooler or transmission, shows temp of 135-140 degrees. Transmission is working correctly and not getting that hot. If left alone, cooling fans will run for about 5 minutes then cut off and transmission temp will return to normal reading on scanner at about 140 degrees. You can drive this thing the rest of the day without any issues. I see on the wiring diagram that the circuit has shared grounds with the line pressure sensor and shift leaver assembly. I am lost as how to diagnose this thing any further. Was sure it was a PCM problem but after replacing it the vehicle came back 4 days later doing the same thing again. It seems others are having this same issue, but unable to find a fix. Has anyone else run across this issue or have any ideas. Thanks R.C.

gsferraro
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Re: 06 Jeep Grand Cherokee 5.7L 545RFE

Post by gsferraro » Wed Jul 12, 2017 5:06 pm

Where did you get the PCM from? I had one doing pretty much the same thing, everything pointed to the pcm, i think i went through maybe 3 or 4 pcm before i got one that finally fixed the car. Gary

brettsb16a2
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Re: 06 Jeep Grand Cherokee 5.7L 545RFE

Post by brettsb16a2 » Thu Jul 13, 2017 3:29 pm

I second that, in the past, I have had to replace more than one ECU on the same exact Chrysler car. Same exact code will set because they all seem to have the same exact problems and the companies are not fixing them when they are sent back. I have had issues with both dealer and aftermarket ecus. Get another and try it.

rc195840
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Re: 06 Jeep Grand Cherokee 5.7L 545RFE

Post by rc195840 » Tue Jul 18, 2017 2:15 pm

Thanks for the reply guys. I am thinking the same thing about the PCM. Don't laugh but I googled the same vehicle with the same code and there are a lot of them out there. Dealer tech's I have talked to say the same thing. I replaced the first PCM with an aftermarket rebuilt one. The company gave a lifetime warranty on it and when I installed the thing an intermittent problem became an all the time problem. Sent the thing back with long letter to the tech explaining this and guess what they sent me another one that has the exact same problem only its back to an intermittent problem. Dealer PCM is no different. Talked to one tech that said the same thing. It took 4 PCM replacements to finally get a good one. No PCM rebuilder that I can find can fix the thing. I had tested the thing so much I know the system by heart. It always happens when the transmission reaches 135 degrees and a voltage change takes place in the PCM. We finally got a used one and the problem went away, customer traded the vehicle back to a dealership. This is a PCM issue and its just pot luck getting a replacement one that is good. Chrysler knows they have a problem with this there are too many out there doing the same thing. Don't think it will ever have a TSB on it though. Live & learn I guess. Thanks again for the input. R.C.

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