If you perform a test drive without a scan tool, you’re wasting your time. If you give a customer a quote on a job without checking for bulletins and updates, you might end up doing a job for free. Today you need to look at the whole vehicle and all control modules associated with powertrain management.
Codes in any module involved in powertrain management may have a direct effect on the operation of the transmission. This includes ABS and traction control modules, too.
And maybe most important, you need to consider the very real possibility that a computer programming issue could be causing the customer’s driveability complaint.
Programmable logic controllers (PLCs) have been with us for at least a half century now. They started as simple logic boxes and evolved into multiple, miniature supercomputers with their own LAN (local area network) systems. With all of the perplexing electronic and mechanical systems that are monitored and controlled by these onboard computers, it’s become extremely challenging for many technicians to keep up.
One common question you need to consider is, “Do I need to reprogram the computer?” Knowledge of programming updates, computer issues, and system resets that need to be performed after working on the car are vital considerations that could turn a simple, profitable repair into an expensive nightmare.
Since this is such an expansive subject, we’re going to break this information into pieces. And to make sure we cover the more pertinent units, we’re not even going to consider the original electronic control units (ECUs) in this article.
The advent of OBD-II marked a turning point for computers and programming that serves as an accurate starting point for discussing programming issues that need to be addressed on a regular basis.
What’s more, beginning with some 2010 vehicles, Global A and B computer architecture began appearing. That means that swapping a “good used” computer may completely disable the vehicle, causing an expensive reprogramming trip to the dealer just to get it functioning. Probably not what you were looking for.
So let’s start with domestic vehicle applications:
General Motors has been a mainstay of technological advances, and the computer power they provide in their cars doesn’t fall short of expectations. GM is the first domestic manufacturer to use programmable logic computers. For the record, all General Motors computers have model-specific calibrations stored in memory.
The older, pre-1990s model units used removable PROM (programmable read only memory) chips, which provide stored powertrain information specific to the vehicle application. This allowed GM to use a universal computer assembly for several different models that required minor programming to make them work in each individual application.
Later model vehicles used EEPROM (electronic erasable programmable read only memory) chips and other non-removable storage imbedded in the computer processor.
Most of these vehicles require VIN-specific programming with the computer installed in the vehicle (figure 1). The new 6-speed units use a dedicated transmission control module (TCM) that resides inside the transmission, mounted to the valve body, called a TEHCM — transmission electrical hydraulic control module.
When you install a new TCM in these vehicles, it must be programmed with dealer-level equipment or equivalent, and the programming must be performed on the vehicle. What’s more, you should never try to drive the vehicle to the dealership after the repair; it may cause premature transmission failure. You’ll need to have the vehicle towed.
It’s also necessary to reset the adaptive values, using a factory or compatible aftermarket scan tool, and you should update to the latest programming whenever you’re using the original computer. This could prevent premature failure and shift quality complaints.
As you can see, it’s extremely important to have a plan in place and a predictable timeline to deliver a job like this in a timely manner.
Ford Motor Company
Ford has proven its ability to use computer technology to create a wonderful driving experience. Ford computers have incorporated adaptive shift strategies since the early 1990s with the E4OD transmission. Since then, adaptive shifting has become more elaborate and complex with the advent of OBD-II diagnostics.
Ford uses a vehicle-calibration-specific computer. Even though all of the OBD-II units incorporate adaptive shifting, only the latest computers offer the capacity to reset these adapts.
The front wheel drive, 6-speed units have an external TCM, unlike the GM versions of the same units (figure 2). This affords greater electrical diagnostic capability, because you can monitor signals in the transmission wiring between the TCM and the internal transmission components.
While most of the 4- and 5-speed computers are plug-and-play, the 6-speed computers require dealer level, VIN-specific programming whenever you replace the TCM. As with the GM units, you’ll need to reset the adaptive values and update the TCM software for maximum transmission longevity.
When working on 6R60/6R80/6R140 units, always make sure that valve body calibration information matches the transmission you’re working on. If not, reprogramming or updating the software may not cure a driveability issue or shift complaint (figure 3).
Chrysler has taken computer control from a basic, non-intrusive level to a totally invasive level never before attempted by automobile manufacturers. The introduction of the 604 in 1989 changed the transmission industry, and it has never been the same since.
This fully electronically controlled transmission showed us how intricately a transmission can be controlled, incorporating engine management systems with transmission controls to produce a best-case shift in almost every situation. The original computers were non-programmable TCMs.
As rear wheel drive technology began to merge with front wheel drive systems, the transmission controls migrated to the powertrain control module (PCM). With the exception of the RE and RH units, all of the PCMs can, and should, be quick learned.
Most of the OBD-II computers have programming update capability. The NAG1 units incorporate a TCM that isn’t programmable, but comes user ready from the dealer (figure 4).
Chrysler PCMs can be expensive to replace and require factory level reprogramming, but aren’t known for frequent failures. Always follow the special initialization procedure for the 68RFE to make sure the TCM resets and adapts can occur.
As you can see, there’s a lot to consider before working on later-model vehicles. The more information you have before you commit to a job, the better prepared you’ll be to tackle the job and deliver the cure to the customer’s original complaint… the first time. This puts more profits in your pocket, keeps your rebuilder on the bench, and gets your customers back on the road where they belong.
Knowing what added programming and relearn procedures you’ll need for a job allows for seamless planning, predictable profits, and fewer no-goes and comebacks. It also opens opportunities for you to offer programming services that can produce more leads for valuable customer referrals.
Computer programming isn’t avoidable. You can’t simply focus on a transmission-only approach; the only way to move forward is to learn, adapt, and adjust.