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Discussion Starter #1
I purchased the mod found here:

http://gm-volt.com/forum/showthread.php?143882-Just-installed-new-model-ERDTT-switch&highlight=ERDTT

I didn't have any trouble installing it, but am getting readings that don't seem at all appropriate and am curious if anyone else that has tried this has experienced anything similar. After install, the car reads -40 with the mod on or off. I did as instructed (to the best of my knowledge). I let the car sit for some time after moving it so it would supposedly be in sleep mode, made sure it was not plugged in, and had the keys some 50 feet away.

Any thoughts on what might be going on here?
 

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Heck it is>than triple digits today where I am...someone is trying to get the jump on winter!;)

-40 C/F is the indication you would expect with the Ambient Air Temperature Sensor removed from the circuit creating max resistance/open. Make a resistance check between the 2 pins prior to installing to confirm the mod assy is working correctly.
 

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Getting a head start, good call.

I'll certainly do mine before winter hits, but am going to enjoy the summer first! ;)

Before removing and checking, as you've done the work already, I'd suggest the following:
1. Park car. Turn off.
2. Plug in to charge. (So engine will not start in next step)
3. Start car. Let it idle there for 30-60 mins to ensure the sensor is being polled. It can be a few minutes before it actually updates from the last known value (in this case, "0"/"null" which converts to -40 as a temperature)

If it doesn't update after a while, then I'd remove it and check the sensor itself as above
 

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Discussion Starter #4
Thank you both for the feedback. Quick test of the assemly says that the switch itself is working - I get a complete circuit in the on position and nothing in the off. Can't comment on anything else regarding the assembly until I find my multi-meter.

Even with it disconnected and the factory set-up in place, I'm getting -40, but no signal from the car that ERDTT. Little bit of conflicting info there, but going to take the advice above and see if it corrects itself with the stock set-up and go from there.

Will update later, if only in hopes of others being able to leverage the experience.
 

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I've seen others post the -40 behaviour sometimes takes driving the car for 30-40 min to reset. If nothing else works, try driving for a while.
 

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Discussion Starter #7
Restoring stock configuration and allowing about 10 minutes of run time produced normal/expected behavior. Gave the car significant down time and put the mod assembly back into service and ran into no issues (yet, fingers crossed). Having experienced the install and the lack of objection, in the form of error codes etc..., I would advise others interested in the mod: Follow the instructions, be patient for 5-10 minutes of run-time afterward and all should be fine.

Thanks for everyone's feedback.
 
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