: Back from the shop - Top Issue

09-10-10, 04:48 PM
Well I have an interesting story about my top repair.

Last weekend while at Panama City Beach the toneau cover would not deploy while putting the top down. After a couple of tries it went down, but after putting it back it was done. It wouldn't look any longer.

This was the first malfunction I have experienced with the vehicle in the year and half that I have owned it. I followed the advice of the forum and found the nearest XLR certified dealer. It was only just over an hour from my house.

The tech check the car and found that the code that control the deployment of the cover was missing! How the heck does computer code go missing? Anyway he phoned someone at GM and they told him to reprogram the top control module (TCM) and that if the vehicle malfunctioned like that again the TCM would need to be replaced. So I made it out of the dealership for 93 dollars and my fingers crossed.

I would love to hear anyone's theory on the code loss and how they think it might have happened.

09-10-10, 08:46 PM
The Folding Top Control module stores the sensor parameter expected and actual positions, compares them and halts the folding top's operation if the actuals fall out of the expected window. It's reasonable to assume the folding top or rear tonneau position sensor values were missing and created your problem. Normally, the last position values the module read are stored in memory and can be pulled with a Tech 2. If a particular sensor parameter is out to lunch, it's a good place to start troubleshooting. If it's missing count (position) data entirely, then the FTC module becomes suspect as well. Most top issues can be traced to a faulty or misaligned position sensor or indicator switch.

It's uncommon, but non-volatile, re-programmable RAM can drop a bit sometimes. Hopefully, it's an anomally and won't repeat. The $93 bucks you paid to re-init the firmware was about a tenth of the Folding Top Control module's replacement cost. --At least you know your top software is current!