Automotive onboard computers, do much more than control the transmission and motor functions. Known as the TCU, transmission control unit-module, in most vehicles the transmission function is the main focus for the TCU. In the early days of automotive computerization, the engine was literally all the on board computer duties included, engine functions.

Modern cars have sophisticated computer systems, some cars even have more than one on-boad computer, in that case their may be a computer to keep an eye on other functions. Ninety nine percent (99%) of them don’t have a Transmission Check Lite. Based on that, the transmission will turn the Check Engine light on.

As I have preached in the past, regardless of what type of problem your car may exhibit, a scan tool must be hooked up to the DLC to determine what the problem is. Other than a good old fashioned visual inspection, in essence, you are spitting into the wind by approaching an automotive problem, or transmission problem in particular without a scan tool in hand.

Unless the car was so old that computerization was not an issue, the first thing I laid my hands on when going to diagnose a customers car was my trusty Snap On scanner, or “Red Cube”.

FYI: For example, every activity the transmission performs on modern cars and trucks is a combination of input signals, easily understood by the TCM to perform the appropriate shift/function at the correct time.

Some of the more sophisticated cars use multiple on-board computers to handle many operations, including taking input signals from wheel sensors so the suspension compensates for bumps and turns in the road for your comfort and safety.

We can see how much computerization has improved the overall function of cars and trucks. Surprisingly, even the giant semi trucks we see on the highway are highly computerized.

With that in mind what is the best avenue to take when it has been determined you need an Transmission Control Unit?  I’m not a fan of buying a computer or TCM from the dealer. Most of the time a computer from the dealer cost an arm and a leg, plus, since it is new, it is nor programmed yet. In effect we can say it is stupid. what I mean is that in most cases the computer you purchase from the dealer for an outrageous price also needs to be programmed. That’s right, another $75 to $100, or what ever the fee is to program the ignorant computer you just payed to much for and were not told about programming it.

People take unprogrammed computers home unknowingly, and install them only to find out that you need to take the computer back to the dealer  and pay for the programming. Oh, they need the car too, and that is a tow bill you can add to the total price. Along with the irritation and frustration.

As a shop owner we made a bunch of customers glow with happiness. We knew that our transmission supplier would sell us a programmed computer for about $100. Right out of a car that has been identified with the vehicle identification number VIN, to have the exact same transmission functions as your car.

The really nice part of all of this is that the warranty is usually one year on a low mileage used TCU, which may be longer than the dealers warranty, and it bolts in, making the car useable again, without towing it to the dealer to get it programmed.

Sounds good eh? Keep this information in mind when you need an transmission repair or transmission replacement. We talk about diagnostics all the time on our GotTransmissions.com Blog, since diagnosis is the most important test your mechanic will perform, much like a doctor will diagnose you before he decides you need brain surgery.

Cars and humans, it is true that there is a common bond between the two. Both pieces of equipment have many separate systems that require strict diagnostic procedures before work is started. Both have to have all systems operating properly to make the entire system work correctly in whole.

Before you buy any old computer, give a call to the transmission supplier who outperforms them all, @ 866-320-1182. Satisfaction guaranteed.