rodnutrandy

If I drive it about 50 miles the overdrive locks out ( saw where it does that if transmission over heats ) If go any further trans overheat light comes on , I immediately shut down and wait to cool . Engine temp does not go up . Is this possibly a plugging filter or more like a line plugged ? any info appreciated , filter was changed at about 125,000 miles

dave1123

It's possible the trans cooler line is plugged or worse yet, bypassed. Most of the heat created in the transmission is from the fluid churning in the torque converter. If this is the case, you can install an aux trans cooler bypassing the radiator cooler. just remember the radiator helps it warm up in cold weather.

There is a thermister, or temperature sensitive resister, in the trans that won't allow O/D (4th gear) to engage when the fluid is below 32*F or above 240*F. When this is triggered, the BCM turns on the overheat light.

Living where I do, there have been times when I've had to drive about 5 miles before it will shift into O/D. I've gotten in the habit of warming it up in neutral for several minutes before I start out for work when it's below zero.

00_WJ_4.0

Well a bit of back-story on the same issue I had with my one wj, I got the jeep and it started doing this right away, I chased the issue for months and changed alot of unnecessary parts before I found the issue... Not knowing the story on your jeep I can't say if the fix for mine, or the issue with mine is the same that you're facing... So I started with the pressure sensor transducer in the trans, and a fluid change. That was the general assumption on the issue from numerous people.
Long story short that wasn't my issue. Easy enough to fix if you have the 42RE but it's built into the valve body in other transmissions.
To sum it up, my pcm was replaced prior to me buying my jeep, and was done so with one from a 99 and my jeep was a 2000. There was miscommunication in the trans and pcm and it was thinking the trans was over temp when it wasn't. I replaced the pcm, ignition and SKIM with those out of a 2000 with similar options and my problem went away.

rodnutrandy

Well , my Jeep was bought new and nothing was changed in the electronics , I changed fluid and filter on transmission and than came up with another problem , my electric fan is not coming on . Did jump the fan and it spins right up , Took what I thought was the fan relay off , but am doubting it now . Number does come back to a airbag or fan relay . But when I look at relays for the fan on sites , it doesn't match , Show 4 wires and this relay has 2 .

dave1123

IDK if your 02 is the same as my 00, but here's where the fan relay is; Some of the newer ones have 2 regular relays in the PDC.

rodnutrandy

Can't ask for more than that , will tackle it tomorrow , Thank you , I have headlight out and wrong relay , I will find the one you show !

dave1123

I bought a Dorman 902-303 from rockauto.com and it came with a new harness plug which I didn't need. It was a while ago so IDK how much it costs.

rodnutrandy

Ok , I bought a new relay and installed it . Did jump the 2 heavy wires at relay plug and fan ran , no way to see if it is getting signal to run . Question is will it run anytime air is on or does it have to get temperature up ? If anytime , I still have a problem .

dave1123

It's a pulse modulated relay controlled by the PCM. It won't come on until the engine reaches 210*, then comes on high. After the engine cools down to 195*, it runs on low until it either gets hot again or you turn the engine off. The fan runs on high whenever the A/C compressor is engaged, but IDK if it will until it reaches temp.

The fan speed is controlled by pulsing the power going to it in short bursts for low speed and steady for high. It's a solid state digital switch, but they do wear out. The trigger signal comes from the PCM, but IDK if it's 12 volts or digital 5 volts.

rodnutrandy

Thank you for all the info. You have no idea how I appreciate the instructions and help . I will take it out and drive it and see if I can get it to come on. Know I could sit and let it warm up , but I have another problem I want to see if fixed .

dave1123

With a standard thermostat, it only takes a couple of minutes to warm it up. Watching it with the hood up is the best way to know for sure.