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2007 Jeep Grand Cherokee No engine crank-Msg of transmission over temp

2007 Grand Cherokee - no previous problem - no work done in last year.
No engine crank - brief dash msg of “transmission over temp” - then msg disappears and vehicle is silent when key turned.
Has happened 4xs in the past 2 weeks. Sometimes will start after a few minutes other times will not start until 24 hours later.
Tuesday drove 20 miles no problem. Stopped car for 2 hours went out to restart and nothing but silence. Brief dash msg of transmission over temp.
Had vehicle towed to dealer. Tow truck driver had never heard of this problem and it did the same thing for him. Dealer had jeep for two days and can find no problem. Started right up for dealer. No fault codes. Live in rural northern Minnesota and afraid to take it anywhere. Can anyone help?

I did a google search and found one guy with same problem but no solution - not a good sign.

I don’t know much about Jeeps in particular but if I had to guess, one of the computers thinks that the transmission has overheated and may not let it be started to protect itself. Some vehicles have that protection mechanism, some do not.
Of course, your truck is stone cold and it isn’t overheating at all so it probably is related to a bad temperature sensor that helps make that decision or the connection to it may be bad.
A dealer should be able to tell you whether that is the normal behavior (ie. when overheating, don’t allow starting) for that truck and come up with a similar conclusion.

This is in series with the Park/Neutral and therefore the car won’t start.

ATF Temperature Sensor

The ATF temperature sensor is a positive temperature co-efficient (PTC) thermistor. It measures the temperature of the transmission fluid and is a direct input signal for the TCM. The temperature of the ATF has an influence on the shift time and resulting shift quality. As the temperature rises, resistance rises, and therefore, the probing voltage is decreasing. Because of its registration, the shifting process can be optimized in all temperature ranges.

The ATF temperature sensor is wired in series with the park/neutral contact. The temperature signal is transmitted to the TCM only when the reed contact of the park/neutral contact is closed because the TCM only reads ATF temperature while in any forward gear, or REVERSE. When the transmission is in PARK or NEUTRAL, the TCM will substitute the engine temperature for the ATF temperature.

Starter Interlock

The TCM monitors a contact switch wired in series with the transmission temperature sensor to determine PARK and NEUTRAL positions. The contact switch is open in PARK and NEUTRAL. The TCM senses transmission temperature as high (switch supply voltage), confirming switch status as open. The TCM then broadcasts a message over CAN bus to confirm switch status. The PCM receives this information and allows operation of the starter circuit.

Google, Cut/paste. So it is the temp sensor, then?

You keep coming up with very good pertinent info for these kind of issues @knfenimore, good job and thanks for the circuit explanation since we don’t have a diagram to look at.

Since the warning alert goes away and the car still won’t start I wonder if the trouble is being caused by a faulty connection to power somewhere for that circuit. Checking the connections to power is usually a good first step for things like this. A simple connection problem can cause a lot of grief and often a lot parts are thrown at the problem before the real culprit for the trouble is found. Just a simple bad connection.

I had this same issue with my 2007 Jeep Grand Cherokee Laredo 3.7L for about 2 years, starting at 6 months after I bought the car used. I live in both Colorado and Iowa and I was constantly afraid of being stranded when I traveled between states. Many mechanics looked into the issue and couldn’t figure out what it was or how to fix it. I had my starter replaced, and that seemed to fix it for a few months but the issue came up again more frequently, even after driving for only ten minutes. My mechanic that I’ve had for many years wasn’t able to figure it out at first, but I took it in again and begged them to look more into the issue before my 12 hour drive to Iowa and they finally were able to fix this problem. According to them, my gas pump was not functioning properly and was not giving enough pressure to the engine to signal that there was enough fuel to start the car. Apparently it should be giving 65-70 pounds of pressure - they found that The pressure never went above 65, and when it was under 50 was when the car wouldn’t start. Pressure had to build up in order for it to start again. It took them 4 days to figure this out. This was not a cheap fix ($900) but having my gas pump replaced completely solved my problem and was well worth it, much cheaper than buying a new car. To anyone else who is having this issue, I highly recommend having your gas pump checked out - it could be the source of the problem. It saved me the continued frustration of never knowing whether my car was going to start or not. I hope this helps!!