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Duramax Discussion

Originally Published in Trailer Life Magazine

Q. Often, after driving my 2004 Chevrolet Duramax diesel 3500 for two or three hours while towing a 29-foot trailer, we stop at a rest area for a few minutes. When it is time to get back onto the road, I find that the cruise control will not engage for up to half an hour. This does not happen every time, but it has happened on a similar 2001 pickup I previously owned and has happened on similar pickups. I have also found that when I turn off the ignition key, the radio will stop playing and the windows will not roll up or down. Because of this, I think there is a connection between the cruise control, window control and the radio.

I have complained to two different dealers and to General Motors, but none of them have an answer, nor do they appear to care very much. They have, though, changed out some parts with no result. Cruise control is very important to me, and I would like to have it fixed.

— B.R., Shelton, Washington

A. When you turn the key off, there is a retain accessory control (RAC) that provides accessory power to the vehicle as long as the door was not opened. The RAC module is like a relay that is controlled by the body control module (BCM). The dealer needs to use a Tech-2 scan tool to find out if it is a signal problem or a control problem in this circuit. This is likely where the problem is.

— K.F.

Ken Freund’s more than three decades of auto-repair experience and 20-plus years of RVing helped him author numerous books and articles on vehicle repair. In addition to RV Clinic and Performance, he writes the Powertrain column in MotorHome magazine. Ken has been a California Automotive VO-Tech and Smog-Test Program Instructor and an ASE-certified Master Automobile Technician.

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