Why do I lose all gears but they will work if I restart the vehicle?
Asked by Guru95DP3B Dec 28, 2020 at 11:23 AM about the 2004 Chevrolet Trailblazer LS 4WD
Question type: Maintenance & Repair
My trailblazer lost all gears while driving down the
road. I pulled over and turn the vehicle off. Waited
a few minutes. Then restarted the car. Gears were
back. Drove home. Car did this 4 times on the way
home. It's been sitting a while and now has a
completely outdated dead battery. But I jumped it
and it still drives... What could it be?
7 Answers
Check engine light on? Pull codes it may lead you right to the issue. Transmission control module?
If you get all kinds of transmission related trouble codes, it's time to get rid of it and move on. A friend had the same thing happen, spent $1,600 on repairs, including replacing the transmission, and it still did the same thing. In the end he junked it and was out all that money. Hope that helps! Jim
Guru95DP3B answered 4 years ago
The thing is, when I hook the OBDII reader up to the vehicle, it's not registering that it's even plugged in... So it doesn't show any codes. Check engine light comes on, next time I drive it turns off... Very confusing, not sure where to start.
Try cleaning the plug. It might be dirty. Hope that helps! Jim
Guru95DP3B answered 4 years ago
I was reading my repair manual. My vehicle was doing weird things the night before my car broke down with the speedometer. I would be on the freeway and look down and it would say that I'm doing 20mph when I'm actually doing 60mph. Could my vehicle speed sensor need replacement? It says that a defective one can cause various driveability and transmission problems...
Yes speed sensor will cause this speedometer issue you are describing. Usually on the transmission
Sometimes also vibration down around transmission and frame wears a spot through on the wiring harness causing shorting out and grounding issues. Do a visual inspection down around speed sensor.
