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Bob, Auto Service Technician
Category: Car
Satisfied Customers: 4087
Experience:  40 year GM Tech. +30 Certified. ASE Master Tech.(expired, retired) Medium Duty, Heavy Line, Retired
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Checked fuses inside and under hood - found nothing obvious

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Is there a fuse or something simple I might have overlooked that could cause this not to work. Checked fuses inside and under hood - found nothing obvious.

You will need a class 2 scanner capable of running function tests to find the problem. Because the system is run through the body control module,there is little that can be tested with a 12 volt test light or a volt meter. A regular code reader won't do it as function tests need to be run on the system to find the failed component. I am enclosing the GM test procedure for you to take a look at, it may help and give you some ideas, but without the class 2 scanner it will be an up hill battle. Note, the blue high lights will not open for you, they are GM access only, thanks.

Customer: replied 10 years ago.
Reply to Bob's Post: Nothing attached?? So there is no fuse for that system that I missed? I push the tow/haul button and no light on the dash comes on, and there is no change in trans performance. Would like to check all the simple stuff first before I have to buck up and go to the dealer. Any other reccomendations appreciated. Thx.
Hi Carlie, I thought I sent you some info last night, but I see this morning that the system did not let it go through. I am going to have to copy and scan the info and then send it to you. It is 4 pages, so will have to send in 4 separate posts. Note the blue high lights will not open for you. You may want to recheck fuses number 5 & 6 in the instrument panel fuse box, they both work part of the body control module, but if the power windows and radio and stuff work I doubt we will find a problem there. The only other component is the trans harness, but that comes in after the tow haul switch and if the trans is working okay, I doubt that also will show any problem. You may want to check the wiring going to the switch, the power goes in on the blue wire and out to the trans on the black. Hope some of this helps, but with the new computer systems, they sure did not make it e-z to test anything. Look for more posts. Thanks
Customer: replied 10 years ago.
At the risk of sounding dumb - help me out with fuses 5&6 - found no numbers labeling them?
Really sorry, GM does some dumb things and I almost wish I could apologize for them sometimes. They should say BCM on them. Will see if I can find a picture of it or something and send, no promises, you would not believe how bad the manual can run you in circles sometimes.

Sorry, may be under the hood, GM isn't very specific.

Object Number: 399920  Size: MF

Customer: replied 10 years ago.
Reply to Bob's Post:

The fuses 5 and 6 are labeled IGN0 and CRUISE (they are OK). See image. I have an appt at the Dealer this afternoon, was hoping to avoid that with a simple fix. Found nothing in dash or inder hood labeled BCM.


Thanks for the photo Charlie, wish GM could do as good a job in the service manual. Yes, I knew what else they controlled, not labeled that way in the manual, the thought was that these items are also controlled by the BCM and there was a slight hope that one of these circuits would maybe have a problem. Wish there was something easier that I could tell you to check, but I am afraid the dealer is going to be your best bet. Systems sure are not what they used to be, battery, switch and motor, etc. I really hope it is an e-z fix for you and not too spendy, but at least with the dealer doing the work, you will have them to fall back on if you have other problems down the line. Good luck with it and thanks for giving us a try.
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