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More Power
06-16-2004, 11:44
I visited the local GM dealer yesterday to have the various modules and computers re-programmed for the current truck configuration. I learned a few things while there that I thought I'd pass on.

The 2001 ECM (Engine Control Module) was overwritten with the same VIN number as that found on my 2001 GMC, as well as the most recent programming offered by GM. One of the updates included code for busy shifting when the cruise control is engaged, reduced idle surge and new code that helps the engine meet emissions certification. The engine appears to run a little smoother with the new code.

The BCM (body control module) was re-flashed with code and updates matching the new VIN, but unfortunately, that did not correct the Service 4WD message. As it turns out, the BCM doesn't have anything to do with the operation of the transfer case.

The TCCM (Transfer Case Control Module) I have installed is not the NP1 version I need for the NVG-263 pushbutton selectable transfer case. The technician determined through interpreting the related troublecodes that I currently have an NP8 module, which was designed for an automatic 4WD system (light-duty all-wheel-drive systems). So, I had them order the correct module. Once that has been installed, all necessary systems should function without setting any related codes. The TCCM is not programmable for different applications.

The programming that came in the 2002 TCM (Transmission Control Module) was left intact. I'm currently using a 2001 ECM and a 2002 TCM. John Kennedy informed me that this combination shouldn't be a problem, and it allows me to upgrade to a 2002 ECM at a later date if the aftermarket programmers aren't able to alter the vehicle speed limiter and engine governor setting in the 2001 module - both of which will need to be altered at some point during the final phase of the performance testing.

I also discovered that my "key in ignition" switch wasn't functioning as expected - though I had not seen any indication of that. I also asked the tech to test the operation of the APP (Accelerator Pedal), looking for the correct range of 0-100% on all three elements of the module. This APP module is one produced for an electronic 6.5, but with the 2001 wiring re-configured to match the 6.5 APP input/outputs. We found that the APP module performs exactly like those made for a Duramax application. I thought it would, but I wanted to also make sure I was getting a full 100% with full pedal.

I had planned to have the dealership update the odometer and hour meter to reflect actual mileage and time for this powertrain. But, the instrument panel cluster can't be altered using a Tech II scan tool. You must remove it from the vehicle and input new numbers using GM's Techline Terminal. So, I thought I'd leave it alone for the time being. The instrument panel had 1930 miles and 67 hours on it when I first powered it up. No big….

MP

More Power
06-19-2004, 10:45
The new TCCM (#12577422) arrived yesterday and was installed last evening. On power-up, the light on the pushbutton panel illuminated the 4H position (tx case had been in 4H all this time), and the "Service 4WD" message did not appear. Switching between 2H & 4H worked as it should. All is well...

The front axle on this truck already had the upgraded newer style electric servo actuator, which is plug compatible with the 2001 front axle harness electrical connector. However, the axle servo did not provide an "engaged" signal when locked. So, I rewired the axle's original engaged switch (which is a separate switch) to operate through the 2001 harness.

While I had the knee bolster off the dash and replaced the TCCM, I wired the cargo lamp switch into the Tow/Haul circuit, since this truck doesn't have a cargo light. Now, a double push on the switch engages Tow/Haul, and another double push toggles it off. I thought this was preferable to wiring in a separate momentary pushbutton switch mounted somewhere else on the dash.

MP

CleviteKid
06-19-2004, 13:50
Double-click to engage tow-haul program . . . which version of Windows is this truck running ;) ? ? ? ? ?

Dr. Lee (we don' neeeeeed no steeeenkin' ca-puuuuters) :cool:

More Power
06-20-2004, 11:37
Actually, the Tow/Haul button on the end of the shift lever in the newer trucks is a momentary pushbutton. The switch contacts just make contact when it is pushed, then breaks contact when released.

The cargo lamp switch is a push-on, push-off button, which requires a double-click to function similar to a momentary sw.

I agree, too many 'puters....

MP