Regen - I'm ignorant

[KathyandDave]

Since we've had the Sierra, sometimes it would lose power, the speed would drop to 60km/h (35mph) and the RPM's wouldn't go higher than 2K. This seemed to happen after moderate hill climbing or stop and go traffic on hot days. The dealer said, "No codes, no problem", patted me on the head and sent me away. Now, finally, I've learned a little bit. It turns out that the regen is a computer-driven process to reduce the particulate ("soot") weight in a filter that's important to some testing required by some jurisdictions to transfer the ownership. Regens start on their own, without regard to the operation of the vehicle at the time. Apparently, we don't notice them if the vehicle is running at highway speed with no load, but pulling the MOnty is different. But, since the computer INCREASES the revs during the regen, which might be dangerous, the regen is cancelled if you touch the brake pedal. Also, the fan goes to maximum speed to cool the engine and transmission during the stressful regen, so we hear a loud fan roaring sound. In my case, I heard the fan, thought the tranny had overheated, so I touched the brake and pulled over to let things cool down. Unknown to me, the regen was then cancelled, but the particulate numbers continued to build, so the attempts by the computer to regen became more frequent. The GM diesel mechanic (at a different dealer) that finally understood my problem started the regen using the GM handheld computer that plugs in under the steering wheel. The count went from 38 grams to 9 grams of particulate, a big drop, since the motor had not likely successfully completed a regen for a long time. I watched the whole process. It took about 20 minutes. The regen made the exhaust system so hot that oil that had slowly leaked under the frame began smoking heavily. That became a repair bill for a leaky transfer case seal. The GM mechanic suggested I go down the street and get a chip that bypasses the regen, since the pollution test it satisfies isn't required to sell a vehicle in Ontario.
Now you know everything I know, which is almost nothing. I'd like to know what others know about this.