'01 Sierra HD Cutting Out

[Tissy]

I have a 2001 Sierra 2500 HD w/ the 8100 big block & Allison trans. It does not have a throttle cable, it operates by a throttle control sensor, in case that's relevant to the problem I'm experiencing. This problem began about a month and a half ago (July '05) quite infrequently at first (approx once a month) but has now progressed to almost once daily. Also, it occurs only in the afternoon on hot days, never in the morning or on days that are cool, (cool by Arizona standards). Also, it seems to happen within 2-3 miles of my start point, and only at highway speeds; it hasn't occurred on surface streets yet. I will be driving along, then it feels like I suddenly took my foot off the accelerator, the BATTERY light comes on, and the tach drops to zero simultaneously. The first few times this happened, it lasted only 3-4 seconds, then resumed acceleration, the BATT light went off & tach read normal, all simultaneous again. Now when it happens, it doesn't resume itself. It cuts off, (the truck actually quits running) I have to shift to neutral (otherwise the trans slows me down very abruptly) and coast off the highway, steering hard because I lose the power steering. This scares me because if it starts up on it's own again like it was first doing, I will get power steering back and am afraid to be oversteering when it kicks back in. After I stop, I shift into park, turn off the ignition and turn it back on. The truck runs fine all the way home. (Approx 25 miles) I have brought the truck to a GMC dealer and they have scanned the ECM and BCM for any codes that might have stored, but there were no codes. Suppossedly no bulletins, recalls, etc...either. But unless it actualy acts up for the technician, they cannot diagnose the problem. Has anyone else had this problem, or have any suggestions? Please don't suggest battery, cable connections or corrosion, that's all been checked. Any OTHER suggestions that may help?? Please? -Kristine

[Ford4x4Chik27]

Alternator....? Could be trippin out on ya

[mrjohnwayne]

Camshaft sensor maybe??? I know it's an apple to an orange, but my 7.3 powerstroke was doing something similar to that. It would'nt shut down completely, but it would "jump" (that's about the best i can describe it) only at like 55 or faster

[Tissy]

No, it isn't the alternator either; I wish it was so simple. Cam sensor is a possibility I suppose, thanks for the input mrjohnwayne. It's hit or miss I guess, I'll just have to wait for it to **** out all together. I just can't afford to replace something and hope that fixes it. Oh well....Thanks for the advice though. Any other input is welcome, I'm desperate! Lol....

[Tissy]

Another odd thing; this week in AZ the outside temp is averaging 98 degrees and my truck has not acted up once. When it was acting up almost daily, the outside temp was averaging 103 or higher. Could this somehow be a factor?

[mrjohnwayne]

Maybe, but I would'nt think that a 5 degree variance in temperature would do it. I have been wrong before though