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Discussion Starter · #1 ·
I had a few days of thinking I ruined my 2012 Volt after doing a mod to the outside air temperature circuit (to stop the ERDTT). It ended up that the mod had nothing to do with the problem, but I didn't know that at the time.

I made the temperature sensor mod under the passenger seat of the car. After about 10 miles of driving, my car popped up with a warning that read "Service Tire Monitor System". I looked at the tire pressures and only one tire showed up. After a couple more miles, even that one went away. When I would go to turn off the car it would not do the usual shut off sounds, the radio would still play after the door was opened and it would pop up with a message saying the Remote was not detected. I discovered the trick was to turn the car back on and immediately turn it off and the car would shut off normally. Then upon exiting the car I could not press the door button to lock the car until about 15 seconds passed. After that time, locking or unlocking the car worked fine. What I eventually realized was, I had gotten a dash cam for Christmas. I installed that on the windshield to the right of the rear-view mirror at the same time I did the ERDTT mod. I thought about it and remembered that the dash cam would stay running for about 20 seconds after the power was cut (from turning the car off). I unplugged the dash cam and the tire pressures showed up within about 10 seconds. All other weird problems went away. So the bottom line is, I love my ERDTT-temperature mod and the problem all along was with electrical interference from the newly installed dash cam. Relocating the dash cam away from the black box behind the rear-view mirror solved the problem. I was pretty scared for a while there.
 

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Glad you solved your problem. Which dashcam do you have and how/where do you get power to energize it?

I bought a G1W-C and mounted it on the passenger side of the mirror in both my leased 2012 and my purchased 2014, utilizing the pto in the dash cubby. I had/have no interference problems and the camera works perfectly.
 

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I had the same issue with a dashcam and a Cadillac.

I figured it was some form of rf interference. I never did solve it but it did seem to be a bit variable so I wondered if the rolling code security modified the rf frequency of the car slightly which then caused variations in the interference. The same dashcam in my Volt has no issues.
 

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Discussion Starter · #4 ·
The Dash Cam is a "ZeroEdge" Z1 model. Obviously not a major brand, but it supposedly had good reviews (it was a Christmas present). I plugged it into the cubby as well, but wasn't sure I was going to keep it to the right of the mirror, so I didn't route the wire anywhere. It just went straight down. After discovering it was the culprit, I moved it to the far right side of the windshield and the problem persisted. I moved it to the far left side of the windshield and the problem went away again. The little black box behind the rear-view mirror favors the right side, so the distance was greater when I mounted it on the left.
 

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No issues here with a Blackvue DR650GW 2 channel going over a year now. The main unit is mounted right below the middle black box. I'm also using the supplied power magic pro mounted inside and wired directly into ACC/12V taps from the overhead console. I never considered an inline fuse as necessary as the power magic pro has a 1A PCB mounted one inside. The Blackvue is a Wi-Fi enabled camera yet it doesn't interfere with keyfobs/TMPS. Infact the coaxial cable that goes to the rear camera module is just Wi-Fi over powered coax.

As Steverino said its the cheap cameras and horridly designed cheap power adaptors that have little noise suppression/non-FCC compliant/fake FCC logo units direct from china that can most certainly be a problem.
 

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Since everyone is focusing on the dashcam, I'll ask about the other half :p

Most people have done the temp sensor mod under the hood/front bumper
Would you mind sharing pics/instructions of how you did it under the seat? (Perhaps write up your own how-to post?)
I know the wire leads back there, but you could save people a lot of trouble identifying what goes where if you could share your experience :)
 

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Discussion Starter · #8 ·
I did my override using Regen's info here: http://gm-volt.com/forum/showthread...wer-value-on-2012s-and-earlier&highlight=dpdt

My only problem with the info is, the conventional way to tell the color of a wire is to first state the solid color, then give the striped color. In Regen's sketch, he reverses that. So I cut a wrong wire before I realized. Also in the sketch, the pin locations are reversed front to back. For your own piece of mind, you can see a couple of the pin numbers imprinted on the underside of the wire connector, just to be sure.

So, I bought 40,000 ohms worth of resistors (for me, 4 x 10,000) and soldered them in series to a small breadboard. I am a computer technician (but not a good solderer), so I had plenty of CAT5 cable laying around. I soldered a couple of wires to the breadboard resistors as well. That became my circuit that shows 28 degrees.

Removing the passenger seat is easy. There are only two torx bolts in the back to undo. One is hidden under a plastic cover. I used a T47 bit. I'm not sure it is the absolute correct size, but it worked for me. I wonder if a T48 would be more snug. Then the seat slides backward slightly to unhook from the front mounts. Under the passenger seat there is a computer with two wire harnesses. We are dealing with the wire harness closest to the center of the car. We need to splice into the wires going to pin 26 and 40. These two wires go to the bumper sensor. There are 20 wire positions per row (not all wire positions have a wire, several are empty). Pin #1 is the corner pin closest to the back driver side of the car, pin #20 is the corner pin closest to the front driver side of the car. Count six pins in from the second row for #26 and take the last wire (closest to the front of the car) from row 2 for #40. I snipped the wires and used common "Scotch Locks" to connect to the wires with no stripping of the wires required using more CAT 5 wire. I followed Regen's sketch for connecting the wires to the switch. There are 6 wires in all. Two going to the stock bumper sensor, two going to the computer and two going the the resistor circuit we made.

The car knows that it needs to be moving to get an accurate temperature reading, so flipping the switch doesn't instantly change the temperature reading. In fact, if you aren't doing over 30 MPH, the temperature will not rise for fear it is reading heat from the engine. The temperature will fall more quickly though because it knows you can't have a false cold reading. I have always been aggravated with my Volt doing ERDTT when I just pulled out of a warm garage. Now I am happy with my winter driving.
 

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Thank you for your write-up. I'll pass on the mod, since ERDTT doesn't seem to impact me very much. I'm retired, so I don't have that daily get-up, get-out every morning and return. Life is good 8^), especially when driving my Volt 8^D
 

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Thanks for sharing - I'll have to check it out by next winter.
This winter I discovered the temp sensor is pretty hard to get out of the slot. I ended up just putting a second modified sensor inside the bumper.
If I can mod from the other end of the wire, it can be much easier to access and I don't need to worry as much as about waterproofing splices and a waterproof switch.
 

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Thanks for sharing - I'll have to check it out by next winter.
This winter I discovered the temp sensor is pretty hard to get out of the slot. I ended up just putting a second modified sensor inside the bumper.







I considered that this ambient air temp sensor wasn't too difficult for me to get to. Just had to roll the Volt onto some low-profile ramps and remove a single bolt in order to gain access to it from directly underneath!?:confused:

Can't say how much more difficult it may be to get to on the Gen2s though...
 
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