With great power comes great responsibility, as Uncle Ben told Peter Parker. The ability to reprogram a vehicle comes with responsibilities, such as ensuring the options the vehicle is equipped with are selected before programming and knowing when a reprogram can correct a problem or will not have any effect. Understanding the application is also important. Programming a module and selecting the wrong options can cause immediate or future problems.
Module Replacement
In many cases, a new module will have to be programmed once installed, and it becomes more frequent as time passes. Manufacturers used to program the modules for the application before you purchased them. The Chrysler J2534 software could only program emission-related modules in the older Chrysler models. It could not program BCM, ABS, or any other module. So, it was plug-and-play when you needed to replace a Totally Integrated Power Module (the TIPM). You installed it, turned the key, and it worked. They came this way because the only tool available to aftermarket shops was the DRB III, a dealer-level tool. Or, in the case of instrument clusters (IC) for GM, you ordered your IC from the dealer, and you’d give them the current mileage. The IC would arrive to you with that mileage. As programming software progressed, it became more powerful and capable of programming modules that were previously not programmable. This allowed the dealership tech and independent shop to order a blank module, install it, and then program through the DLC port, using the VIN to identify the correct software. The older method took time because the options list had to be identified, the module programmed for that VIN and options, then packaged and shipped. The new method would, in theory, get you a module quicker but require a bit more time and labor once you get it. Remember, if it was once plug-and-play, it’s possibly changed and has to be programmed on installation.
The easiest way to identify if a new module needs to be installed is to look for U codes for loss of communication with that module. This is not looking for a TCM to have a U code for a loss of communication with itself but instead those modules that share data with the TCM, such as the Power Train, Body Control, and Anti-lock Brakes.
A new module is shipped with a program that will identify itself to other unconfigured modules. When the reprogramming software communicates with that module, it will accept a program. For example, an unprogrammed TECHM in a GM can be identified in the PCM as having an unconfigured code for TCM. This means there was communication between the two modules, and when identifying itself, it has a code that shows no vehicle software is loaded. If the code U0101 Loss of Communication with TCM comes up, that tells you the module is unavailable on the network, AKA CAN). This is where you check for power and ground to the module as well as the CAN wires.
TIP: One of the most common faults we get calls on the GM 6T series with a U0101 that wasn’t present when the vehicle first came in is due to the vehicle harness’s terminal spreading apart and losing contact with the pins on the TECHM. The reason is that the rotating lock and position of the tech, from above or below the transmission, can cause a natural roll of the harness. So, as the harness rolls out of the connector, the last pins are the CAN wires. Resizing the terminals will correct it, but removing the connector as close to 90° from the TECHM will minimize the chance of terminal damage.
The Unknown
Say you have a transmission with an annoying bump on an upshift, or it has a downshift clunk. Your customer says it didn’t do this when he bought it, but it started shortly before transmission failure. Now that you have the transmission rebuilt and installed, you’re finding the same conditions exist. There are no trouble codes, and you’ve performed relearns and resets, which, at best, give temporary relief. Before replacing the valve body or transmissions, your first step should be to check TSBs for the transmission as well as engine and brake systems. An updated program for the PCM may address how data from a sensor on the engine is used in determining engine load. As sensors age, their signals change slightly. They may still be within normal operating tolerances, but that signal may skew up or down on the voltage return. The computer can calculate this data and determine that there’s more load on the engine and compensate by requesting more line pressure in the transmission. This, in turn, often results in a bump, clunk, or outright hard shift, up or down. With programming, sensor data can be recalculated to allow for some variances in the signal return.
What if there is no TSB? It’s not uncommon for a manufacturer to release updates without a TSB associated with it. It will require some sleuthing on your part. In some cases, you can read the current software part number under module information through your scan tool. Generic OBD II can display this. If the manufacturer has a website where you can enter your VIN and see what updates are available, you can then compare the updated part number to the one you retrieved through your scan tool. If the manufacturer does not have the information available through its website, you can call your dealer’s parts department and see if they can look it up for you. If that strikes out, then it will require the use of the J2534 tool and manufacturer software to check for available updates (for a fee). If there’s no update and you had to pay to find out, you can bill that out as an “Electronic Information Access Fee.”
The Useless
A program update will almost never correct a faulty sensor or circuit. The exceptions are rare, such as when a sensor is prone to giving a faulty signal and a program change is made to ignore that sensor data and use working sensors to accomplish the same job. You’ll find that in those cases, there is a TSB to address that problem. However, programming is not the answer if it is a hard fault, sets codes on startup or use, circuit faults, etc. A frustrated tech who has thrown parts at a problem and missed may come to you and say it needs programming. Check before programming because if there’s a physical fault with the vehicle, you will now be diagnosing and repairing the car yourself.
Hard faults are 99.9% unrepairable with reprogramming. There are a few exceptions, like when a sensor has been troublesome, and the manufacturer has determined to omit that data and use other vehicle data to accomplish the same thing. We’ve seen this on the 5R110W, where the 2003 models had pressure switches in the valve body and later years did not. Ford found during testing that they could accomplish the same results by monitoring speed sensor data.
No communication with module codes are never programable fixes. The same connection between modules to share information is the same connection the programmer uses to communicate and update. If the module can’t be called up, you can’t send a program to it.
To recap. If there are new modules or if there is a TSB directing for an update, reprogram those. If there’s a faulty sensor, poor wiring connection, or wire condition, do not program unless a TSB counters this. The other situations become a judgment call; a program may or may not correct a condition. Be aware that the time and money spent could yield no solution. Or there was an undocumented change in a program, or the act of programming can reset all learned values. In these cases, when we don’t know if a program addresses the issue at hand or just simply did a ‘reset,’ you must thoroughly test drive the vehicle and complete all relearns. Some emission-related relearns require two cold-to-hot drive cycles to complete.
