Help with 05 Tahoe jerking & losing power

salinay

I need help with my 05 Tahoe. I was on the freeway driving about 80mph & it started to jerk a little as if it was having a hard time shifting gears. It was subtle at first but then it got worse. The door locks started cycling thru, I was losing speed & power. I was able to pull off to the shoulder. I put it in park & then I tried to at least coast off the freeway onto surface streets. I put it in gear & it ran normally. Ithe jerking felt like the engine was going to drop right out from under the truck. It didnt happen again until weeks later again at 80mph on the freeway. Then it ran normal again until this past Friday. This time the engine completely shut down, tackometers were going crazy, doors cycling and after the engine died, it killed the battery too. I had to be towed to the dealership. I had the transmission rebuilt last year. The dealership ran it thru the diagnostic comouter & it was fine. They said the battery was too small for the tahoe so they replaced it & then they said it was the alternator. They reset the entire computer system & restored all the tackometers and tested the alternator again & it was good. This morning it happened again at about 70mph. Was able to drive if home normally. Taking it back to dealership tomorrow. I don't think they really know what's wrong. Does anyone have any suggestions or thoughts?

thecardoc3

The battery going dead was easily part of the symptom. It was probably going dead before you stopped because the door locks cycling and the gages getting erratic are hints that the modules that control those functions were resetting. When a vehicle experiences a computer reset such as you described its commonly caused by a loss of system voltage when it occurs to more than one module. A charging system failure (alternator) would be a plausible cause, but its not the only one. How much time has passed between the previous repairs and the next symptom event?

salinay

Between the 1st & 2nd occurrence it was about a month. Between the 2nd 3rd time was a matter of weeks and between the 3rd & 4the time was 3 days. It was after the third time when I was stranded on the freeway that I took it to the dealership and they changed the battery. The very next day the 4th time it happened. Took it back to them the next day. After some research, we led them to the crankshaft positioning sensor being bad. The ran a diagnostic again and this time the error code for that sensor came up as did a few others. They replaced that sensor and said it should be good now. I'm not 100% comfortable with their fix given they had no idea to start with and we had to lead them to the crankshaft positioning sensor. Time will tell. Thank you your feedback. It's been frustrating and scary driving it. 

thecardoc3

This is the potential problem if someone makes an educated guess and they happen to get it right. Without real proof you are in a position where you can't trust the car to get you where you want to go.

Could the battery have been dead because you had tried for an extended time to restart the car and drained it?

There appear to be a lot of unanswered questions to me at this point.

salinay

I really don't trust the car. Thankfully I have a 2nd car but when I go out of town I drive the Tahoe. Not now. There are a lot unanswered questions and the only way to know if it's truly fixed is to drive it and see if it happens again. If it happens again, I don't know what else to do or where to look. 

Oh oh and the battery was fine and has been fine. I bought it new about 2 yrs ago. It only drained this last time when I was stranded on the freeway. That was also the only time the engine completely shut down too. 

Thanks again for for your responses.