Pretty frustrated. I want to sell my 2007 H3, but I know it needs some TLC, so I took it to a mechanic for diagnostics thinking it would be nice for a potential buyer to see all that needs attention. Also, it would help me set the price. They had the vehicle for 13 hours before calling me to discuss the findings, which I thought was quite a long time for transmission, check engine, and 40 point inspection.

When I brought it in the speedometer would act erratic, fluttering in a 20mph range. When I got it back the speedometer doesn't move at all and you can feel that it is affecting the truck. I called about it and got the usual 'the speed sensor probably went out' because they had diagnosed the erratic behavior as a potential speed sensor issue. Keep in mind, I replaced the speed sensor two years ago to fix the erratic speedometer issue and it didn't cure anything. I just tried replacing the existing sensor with a OEM AC Delco and nothing changed, so obviously I am calling again on Monday as I did not receive the vehicle back in the same condition.

In the meantime, does anyone know what would cause a speedometer that was erratic for years to suddenly stop working completely once in the hands of mechanics? Could this be related to the other sensor that is much harder to get to (I think it's called the input sensor), or something else they disconnected during diagnostics and failed to reinstall correctly?

 

the cluster servo motors go bad. your cluster might need a rebuild. very common issue for gm.

 

Shorted the sensor by power probing the connector? Regardless, you've been having an issue before diag and replaced the wrong sensor. Replace the 2134336 and move forward.

 

 

Thank you all for the replies.

I went ahead and had them replace the input speed sensor that sits on top of the tranny thinking that could solve two issues - the speedometer and the hard shifting/slipping. Dropped it off on Friday and said I would pick up on Wednesday since I was going out of town. Never heard anything so I called Wednesday and was told the sensor did not fix the speedometer so they were looking at the cluster. Didn't hear anything today so I called again and was told the same story.

Tomorrow I'm going to call and talk to the manager because I'm getting the impression there's something they're not telling me. They've had the vehicle almost a full week and don't seem to have answers and won't communicate, so I'm thinking they know they messed something up and are trying to get it fixed without admitting fault.