What does the "trans over temp" light mean?

Surprising .. I'm in the UK and have just been to look at some cars that will be coming up for auction. One of them is a 4 litre '98 jeep with 86,000 miles on the clock and which I'll be able to pick up for around $350-$400. And when I get home I find an email from the fixya team ..

I've never owned a Jeep before and 'googled' your problem. There's no definitive answers to the problem and you're certainly not alone in having the 'trans over temp' warning light.

In a nutshell it means 'transmission failure'.

However, I would suspect that your transmission is fine and the problem is electrical - in one of the chips to be exact. I would further add that you know your vehicle - how it drives, 'feels' and responds. If you yourself feel that the vehicle drives and 'feels' the same you probably have nothing to worry about. In other words, that warning light is a false error message.

You will read on various forums about error messages - warning lights on your dash - that can't be identified using diagnostic equipment. That's simply because hand-held diagnostic devices don't work by magic; they can't diagnose (and reset) certain error codes simply because they can't cater for all vehicles.

You will also read that even dealerships can't identify and cure the problem. Here in the UK the Volvo 960 3 litre (1990- 1997) was notorious for having a 'transmission failure' warning light suddenly appear. The Volvo dealerships/workshops could reset the warning light - but not on all models. Nobody knows why not.

Back to your jeep ...
If you're not losing transmission fluid and it changes up and down as per normal, it's working fine. Changing the transmission fluid is good for the health and longevity of the transmission unit but it won't cure your warning light problem - nor will changing the cooler or any other bits and pieces.

I'm 95% certain that your warning light problem is electrical .. i.e .. in a computer chip. For whatever reason it's telling you that you have 'transmission failure' when you don't. In the event of your vehicle driving as normal, don't worry about it.

Back to the UK Volvo 960..
When these cars reached a 10 year old mark - for whatever reason - the 'transmission failure' warning light began appearing. I bought a 12 year old model and two weeks later .. yes, that transmission failure warning light appeared. Several workshops tried to reset the error code but couldn't. I spent a lot of money and time changing bits and pieces. It made no difference ...

My wife bought an older, pristine, low mileage Volvo 960. A couple of days after buying it .. yes .. 'transmission failure' warning light. I changed nothing. The warning light could be reset, but always came on again a couple of weeks later.

The cure came in the form of some black sticky tape and a pair of scissors. I cut a square of black tape and stuck it over the flashing warning lights on both cars. We drove them for the next seven years.

Back to your Jeep..
You know how the car drives and feels. In your position the only thing I would do would be to buy a can of electrical contact cleaner spray and clean every electrical lead on the transmission and around the engine bay, giving them all a 'tweak' just to make sure they are earthing/connected properly. I wouldn't expect it to make one iota of difference .. but we always live in hope.

It's worth a shot taking your vehicle to the dealership/a workshop to see if they can reset the error code that causes the warning light, but don't bank on it. Give it one shot.

This warning-light syndrome isn't uncommon. Different makes and models have their quirks. The Saab 2.2 turbo diesel, for example, will illuminate the engine management warning light to tell you that the EGR (exhaust gas recycler) is faulty when it isn't. The same engine is used in Vauxhalls which don't have the engine management warning light appearing for no reason. Different chips or whatever ..

Whatever you do, don't panic. The best thing in the vehicle is you ... you know how it should drive and feel. If it continues driving ok ... ok.

Personally, if I pick up that '98 Jeep from the car auction in a few days and I find that the 'trans over temp' light' (probably means transmission overheating) comes on, all I'm going to do is cut a one inch square piece of black tape and ...

YOUR TRANSMISSION ITS OVER HEATING,,I HAD A SIMILAR ISSUE WITH MY 99 GRAND CHEROKEE,,THE OVERDRIVE WASNT WORKING,,SO I ENDED UP TAKING IT TO A MECHANIC,,HE SCANNED IT ,,AND THERE WAS SOMETHING WRONG WITH THE INGNITION COILS AND I THINK IT WAS A THROTTLE SENSOR,,I ALMOST CHANGED THE TRANSMISSION ON IT ,,BELIVE ME YOU ARE GOING TO SAVE A LOT IF YOU GET IT SCANNED ITS WORTH IT

The transmission is over heated , check the fluid level and check that the cooling system is working correctly as there will be a trans fluid inter cooler which may not be operating correctly