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Gary
Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 15695
Experience:  GCM master tech over 25 years
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2002 gmc envoy with 4x4 service light on, no 4x4 switch

Customer Question

2002 gmc envoy with 4x4 service light on, no 4x4 switch light operation, 4x4 inop. had c0550 code only. chamged tcscm with dorman preprogrammed, plug and plat tcscm. 4x4 service light no longer on. still no switch lights nor does the 4x4 work. now have
a u1000 class 2 serial communication problem. i saw this question answered before and a 14 step flow chart was offered in that answer but was blank. could you provide me with a flow chart to diagnose the condition. I have acess to all data and mitchell and
niether offer a specific step by step procedure for this code.
Submitted: 1 year ago.
Category: GMC
Expert:  Gary replied 1 year ago.

the last step # ***** is to try to program the TCCM if you can not to replace it and reprogram it

since this TCCM is new and supposed to be programmed for you can you unplug the TCCM and see with the key ON if the orange wire shows 12 volts at it ? and see if the solid black is a good ground ?

Customer: replied 1 year ago.
orange has battery voltage and a good ground. i can communicate with tcscm to the point where it will give me menus but if i try any funtions like command the switch lights on or engage front axle, ect., it wont do those things. checked class 2 wiring between pcm and bcm, and tcscm and pcm all have continuity. i believe wire color was yellow bcm to pcm and dark green tcscnm to pcm. dont let me get you off track though, i might be jumping around the proper order of diag. i looked at wiring diagrams to figure out which wires were involved. i am an ase certified tech myself but electrical is not my strong point.
Expert:  Gary replied 1 year ago.

you are correct the dark green/white wire is the communication wire from the TCCM

since you can communicate with the TCCM that wire is good and the power and ground is good

make sure the switch shows 12 volts with the key ON at terminal H and that terminal D is a good ground

if those check out replace the switch if it still does this and sets the U1000 and you CAN communicate with the TCCM the programming is bad or corrupt in the TCCM or the TCCM is defective

Customer: replied 1 year ago.
ok i will check those circuits. just to understand you are talking about the terminal h and d at the switch not coming out of the tccm correct? also just wanted to mention with the original tccm that had the 550 the switch lights would illuminate briefly upon turning key on only. don't know if that info makes a difference to the last instructions you just gave me
Expert:  Gary replied 1 year ago.

correct

since you CAN communicate with the TCCM the TCCM power and ground and communication wire is good

and this would narrow this down to the switch not having the power or ground or a defective TCCM or the programming in the TCCM is wrong or corrupt

there is not anything else to cause this issue and the U1000 code

Customer: replied 1 year ago.
the fact that i can acess the tccm menus constitutes communication and there is no chance the pcm or bcm areat fault? I will perform those checks and get back to you on the results.
Expert:  Gary replied 1 year ago.

that is correct

the PCM or the BCM are not any fault at all

it is one of the things i said

Customer: replied 1 year ago.
ok I have power and ground at the switch. what a pain in the ass to get to the switch, remove consolw ect..Will have a new switch at 3 pm. I took the switch apart. the board looks good no visible breaks in circuitry. looks like a simple switch, not much to it.. doesn't have have any burn marks or any defects that are obvious.we will find out at 3:05.
Expert:  Gary replied 1 year ago.

Sounds good

Customer: replied 1 year ago.
well the switch didn't fix it! I had my parts house warranty the dorman tccm with another and still have same problem! now what?
Expert:  Gary replied 1 year ago.

can that TCCM be programmed in the truck instead of being pre programmed then plugged in with a programming scan tool and software ?

Customer: replied 1 year ago.
I have a snapon solus ultra and i don't see on any of the tccm menus option for programming.. these dorman tccm's are supposed to be plug and play. i understand at the dealer they link tech 2 with a pc to download software to be loaded onto tccm.. it is possible my scan tool does not have programming capabilities.
Expert:  Gary replied 1 year ago.

that is where our problem is

these TCCM's are NOT plug and play

the programming MUST be installed with either of these 2 programming options which requires a desk top or live time software to install the programming into the scan tool then programmed into this TCCM

again that is where the problem is the programming is NOT programmed into the new TCCM

  1. Connect the scan tool to the vehicle.
  2. Power-up the scan tool and select the Service Programming feature.
  3. Select the appropriate vehicle.
  4. Press the Request Info button on the scan tool.
  5. Connect the scan tool to the computer station.
  6. Follow the menu select items for reprogramming and provide information as to what type of device you are programming and whether you are reprogramming or replacing the Electronic Control Unit (ECU) .
  7. Select "vehicle" from the selection menu.
  8. Select the module you wish to Program.
  9. Select "Normal" for Programming Type.
  10. Select the applicable software calibrations.
  11. Transfer data file to the scan tool.
  12. Reconnect the scan tool to the vehicle.
  13. Turn ON the ignition, with the engine OFF.
  14. Select the Service Programming feature on the scan tool.
  15. Press the Program button on the scan tool.

Programming Using Scan Tool Pass-Through Connection

  1. Connect the scan tool to vehicle and power it up.
  2. Connect the computer station to the scan tool.
  3. Select "PC Using Scan Tool Connection" from the programming menu on the computer station.
  4. Follow the menu select items for reprogramming and provide information as to what type of device you are programming and whether you are reprogramming or replacing the Electronic Control Unit (ECU) .
  5. Select "vehicle" from the selection menu.
  6. Select the module you wish to program.
  7. Select "Normal" for Programming Type.
  8. Select the applicable software calibrations.
  9. Transfer data file to the scan tool.
Customer: replied 1 year ago.
I know the factory tccm I would get from the dealer requires programing. advanced auto parts sells these as preprogramed and ready to install. part comes from Dorman part # ***** how do i find out if they are programable? these directions for programing with scan to need to be done with a tech 2 or can it be accomplished with a snap on solus ultra? I have a pc and a lap top where do i find the reprograming progran?
Expert:  Gary replied 1 year ago.

the programming capabilities are purchased either as a monthly fee or a pay as you use

for the solus i would contact Snap-on and see who which they recommend to use with there scan tool

i have just always used the GM programming

all of these TCCM's need the programming installed into them for them to work correctly

Customer: replied 1 year ago.
if i got a used tccm from salvage yard would it still need programming?
Expert:  Gary replied 1 year ago.

yes

used or new the TCCM need to be plugged into the truck then programming installed

Customer: replied 1 year ago.
where can i purchase the programming capabilities
Expert:  Gary replied 1 year ago.

search online

but i would contact the local Snap On rep for which programming company's they prefer that will work best with your scan tool

Expert:  Gary replied 1 year ago.

how are you making out ?

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