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PCM replacement in a 99 STS


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I have been here before with this subject and I have read Logans description of a PCM replacement

in the 2000 Eldorado. I - being just a home mechanic tried to help a friend with his 99 STS that have charging problems which is said to be depending on a faulty PCM. A used PCM was tried but the engine did not start. For the moment even some specialists work with the car but they can't get beyond the 'Theft system'.

According to Logan (if I understand it right) the car is needing a NEW PCM where the VIN has to be programmed into it: By GM or where can such a clean PCM be found. Here in Sweden we have problems to find the people with the right deep knowledge.

/Jan L

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Here is the GM TSB. It is #02-09-41-001.

Subject: DTCs B1001, B1271 or B1780 Set When Replacing/Reprogramming Other Modules

Models: 1999-2003 Passenger Cars and Trucks

with Class 2 Serial Data Communication Between Modules


This bulletin is being revised to add model years and reflect changes in the Tech 2 procedure and filing classification. Please discard Corporate Bulletin Number 99-06-03-010A (Section 6 -- Engine).


Class 2 Serial Data Communication allows control modules (i.e. the Powertrain Control Module (PCM), the Body Control Module (BCM), the Dash Integration Module (DIM), the Instrument Panel Cluster (IPC), the radio, the Heating, Ventilation and Air Conditioning (HVAC) Controller, and the Sensing and Diagnostic Module (SDM) to exchange information. This information may be operational information or identification information. Among the identification information exchanged and compared within these modules is the Vehicle Identification Number (VIN). Typically the one module, the master module, broadcasts the VIN and all the other modules compare the VIN stored within itself. When the broadcast VIN does not match the VIN stored within the SDM, the following actions occur:

• DTC B1001 Option Configuration Error is set and deployment of the airbags is inhibited.

• DTC B1271 or a DTC B1780 Theft Locked.

The VIN information is also used by the radio. When the VIN does not match the VIN stored within the radio, DTC B1271 or DTC B1780 is set and the radio is inoperative.

Additionally, the master module will compare the SDM's part number (last four digits) to determine if the correct SDM is installed in the vehicle. If the SDM is the wrong part, a B1001 will also set.

This situation may occur when a vehicle is being repaired. When a PCM or a body control type module is replaced, the VIN information must be programmed into the replaced (new) control module. A module which has had VIN information entered into it (for example, one taken from another vehicle) cannot be reprogrammed. VIN information can only be entered into new modules. The ignition must be ON in order to program the control module. Since the VIN information is broadcast when the ignition goes to ON from any other ignition switch position, DTCs may be set in the SDM and/or the radio. Therefore, always follow the specified control module replacement procedures.

After completing the repair, turn OFF the ignition for at least 30 seconds.

Turn ON the ignition and check for DTCs using a Tech 2® scan tool.

If DTCs B1001, B1271, or B1780 are present with a history status, DO NOT REPLACE THE SDM OR THE RADIO.

Clear the DTCs from all modules using the Tech 2 scan tool.

Remove the Tech 2® from the vehicle

Ensure the proper operation of the SDM by turning OFF the ignition and then turning ON the ignition. The air bag warning indicator should flash seven times and then go OFF.

Refer to Corporate Bulletin Number 99-09-41-001 for additional information regarding proper reprogramming of the new/replaced module.

Clearing codes from the other modules is part of the replacement and reprogramming procedure for the replaced module. The repair is not complete unless all codes have been cleared from all modules.


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I went to the dealer, they tried and it did not work. The tech said it is the replacment PCM is bad it took most of the program then quit.I asked him if they have replaced PCM's from other vehicles with any sucess, He said yes but they are touch and go He believes the problem with used PCM's are the way they are handled when they came out of the donor vehicle moisture, dropping them, or cutting thru the wires going to the PCM while there is still power to it. But he said he has had others go in with no problems and work fine. The one I bought the man said he will send me out another one no charge but I 'm out the 89.00 the dealer charged me to try. I will give it another try as soon as my replacement arrives and post back.

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Probably it is so that a new PCM is needed just as Logan described it as even the specialists over here in Sweden have the same problem with a used PCM. I have left Logan's instructions to the guys doing the job hoping it will give them some hint of the problem.

The original PCM is letting the car start and run beautiful but is sending warnings about charging fault

even after changing the alternator to a new one. With the used PCM that I tried the car did not start at all so I realized the problem is to severe to be solved by me. /Jan L

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