My Mechanic said I need to unplug SGII asap

[RandomFact314]

So most of us have our SGIIs plugged up 24/7
I took my 97 Accord to the shop b/c my Coolant Temp reading on my SGII was going crazy, jumping from 40° to 220° to -12° all in an instant, so I thought my Coolant Temp Sensor was broken...
I called the mechanics the next day and he said the sensor was fine b/c the actual gauge on the dash read perfectly fine

He said there was a short in my SGII and said I needed to remove it asap b/c if it shorts out it will short the computer in the car.

He said he didn't understand why I needed one at all and I said so I can see the direct readout of my MPG and he said that its not worth it b/c there are no computers meant to just stay hooked up to your OBD2 port all day

~opinions please~

[Arragonis]

Mine has been in permanently except for 10 minutes on another car since I got it in June, no issues with the car at all. In fact its been in so long the velcro strip glue has dried out and no longer sticks.

Did / Does the SG2 show any error codes from the car, did he put in another analyser / analyzer to check for any error codes ?

[RandomFact314]

Yeah I think the code was P0118 which was a Coolant Temp Sensor code, but he says it only reads that b/c the SGII is broken

[SentraSE-R]

If I were you, I'd unplug it and contact SG tech support. I've kept my SGIIs plugged into 3 different cars with no issues. Linear Logic should be able to determine if their unit has an internal short.

[metroschultz]

Your mechanic is lazy and looking for any reason to avoid work. (ie. spending time for a true diagnosis.
I had my SGII hooked up for 2 years before I sold it. (the SG, not the car)
The SG does not run its own diagnostic, it pulls from your onboard computer.
Get a scan at your local auto parts store for free and see if it concurs with the SG.
My $.02.
Schultz out.

[t vago]

I'm going to go out on a limb here, and state that the SGII had nothing at all to do with the OP's coolant sensor problem. Not sure how Honda tests their sensors, but Chrysler does rationality tests on the sensor itself, not the data being transferred over the comm bus, to determine whether to throw a code. It would make sense that Honda does a similar thing as Chrysler.

The SGII only talks over a two-wire (or one wire) comm bus. If anything, you'd see some code for faulty or grounded data bus, or something.

[Ford Man]

Knowing a little bit about cars myself I also think it's the sensor instead of the SG II. I know many cars have two sensors for the temperature, one that sends the signal to the ECU and another one that sends the signal to the dash mounted gauge. If the one sending the signal to the ECU is bad and the sensor for the gauge is good that would explain the SG II getting crazy readings while the temperature gauge reads correctly. I'd suggest checking to see if your car does indeed have both sensors. If it does replace the sensor that sends the signal to the ECU. I keep the SG hooked up continuously on my '97 Escort and have for probably about 2 years and never have had a problem. The SG in itself has nothing to do with the readings it receives all it's information comes directly from the ECU and the sensors that supply the information to the ECU.

[Arragonis]

Going with the age old philosophy of changing the cheapest part first, switch the sensor. It will be a pull / screw out and replace part somewhere, and probably quite cheap.

[JasonG]

T_Vago said it right.
If it was the SG or its cable you would get a comm buss error.
I would suspect the sensor first, if that doesnt fix it then its a pinched/ broken wire.
If the SG really caused the issue, why are there no other rolling faults?

[brucepick]

I had similar issues and resolved them.

I had really odd behavior on my SG (in '97 Civic) for many months and finally got it handled. Before resolving it I sent it back to Linear Logic twice, they also sent me a second connecting cord to see if that helped. NOTHING that Linear Logic did helped. Though I must say they treated me extremely well. They volunteered to provide all those parts mentioned above, when I called with issues.

What helped was to install relays to power the headlights (both high and low beams) and the horn directly off the battery (via fuses of course). No kidding. Or, short term, just leave the headlights on and don't fool with them, and don't blow the horn. See if the SG behaves better.

I finally noticed two things.

1) The ScanGauge would lose its "Mode" setting. With that setting lost, it would land on some random mode setting and then show silly output. Go through your SG settings and find what "Mode" it sets itself to automatically, in normal operation. Then manually reset it to that if/when it ever messes up. Use the "Force" option to do that.

2) It would lose the "Mode" setting after I used the horn, or after I flashed my lights on and off (don't ask). So I put 2 and 2 together and figured out that SOMEHOW the significant increase in current draw was dropping the voltage available to the SG low enough (or dropped it nearly instantaneously) so that it "forgot" its mode setting.

I considered finding the 12V pin on the OBDII connector and supplying a good solid 12V to it directly. But my electrical skills being what they are, and knowing more about use of relays than I do about how to work with tiny wires in cramped quarters, I went with the relay option. Problem solved. Um, as I also know that the OBDII system is connected directly to the computer, I kinda don't want to mess with its wiring. But that's just me.