Shift Pointers
- Author: Pete Luban, ATSG Technical Supervisor
At this point, everyone is familiar with the fact that most 1996 and later GM vehicles are equipped with computers that must be programmed (flashed) in order for the vehicle to operate properly.
What some technicians may not be familiar with is the fact that earlier GM vehicles were equipped with PCMs that are also flashable. As a matter of fact, you could have a GM vehicle as early as the 1993 model year that is equipped with a flashable PCM. This is mostly because GM was the pioneer in developing the EEPROM and the programmable process.
I’m sure most of you have experienced the following course of events: You get to the place in your diagnostic procedure where you have determined that this vehicle needs a computer. Let’s say this is a 1994 Cadillac Brougham with a 4L60-E transmission and a 5.7-liter engine.
You trot down to the local GM dealer and buy a new or remanufactured computer. You know there is a core charge on the original computer from your phone conversation with the dealer parts person when you checked on price and availability.
So to avoid paying the core charge, you take the original computer with you and leave it with the parts person.
You now return to the shop and plug your newly acquired computer in, and guess what – the car cranks but will not start. So maybe you call the dealer parts person or your tech service and you’re told that the computer must be programmed in order for this vehicle to even start, much less operate properly.
Sooooo, now you have a decision to make: Do you run down to the dealer and get the original computer back, plug it in and drive the vehicle to the dealer, assuming it is drivable? Do you tow the vehicle to the dealer in its present condition and let the dealer technician have his way with it and pay the labor charge. Do you have someone in your area who has what it takes to flash this computer and ask them for a favor? Or do you borrow this equipment and give it a shot yourself, realizing that if you are unfamiliar with the reflash process you could conceivably toast the computer you just bought? What a pain in the neck.
It would be nice to know going in that you’re working on a vehicle that is equipped with a programmable computer. Check out the charts in figures 1, 2 and 3 that indicate which 1993-1995 vehicles are equipped with programmable computers. The chart in Figure 4 lists the cars and trucks represented by each body code.
One final note: Not all 1996 and later vehicles are equipped with programmable computers. Vehicles that do not have programmable computers include medium-duty trucks like the GMC Tiltmaster with the Electromatic or Aisin Seiki transmissions, Cadillac Catera with the 4L30-E transmission, and GEO models.
