From a post on BITOG. Any insights on validity? I use an UG and as far as I know my cars have had no serious side effects over hundreds of thousands of miles. I have posted this here before...just an FYI Before this year, I was all for things like this. I even went out and bought my own tool just for monitoring my vehicle while I was driving. I used it quite a bit, and still use it to pull codes, and check on general vehicle health. I used to have it plugged in ALL the time in my truck. Here is what I had. http://www.scangauge.com/ Now…I no longer drive with it plugged in unless I am actively trying to solve a problem. I was at a week long training course at the SAE headquarters in Detroit. I was asking some questions about vehicle networks and communication, and earned myself the opportunity to meet a very high up engineer at a foreign car company. He was specifically at the SAE headquarters to meet with the heads of several insurance companies in regards to the “passive” scanning devices that you plug into your OBDII port to get a discount. The short story is…anything plugged into that port disrupts vehicle communication. The OBDII port is just an interface into the vehicle network (it’s a node on the internal vehicle bus) – think of it like a gateway. Well, different nodes on a bus have different priority. That makes sure that important messages like vehicle speed, throttle position, AIRBAGS going off, etc. has a HIGH priority, and their messages can actually kick messages of lesser important off the bus. Well, the OBDII node is the HIGHEST priority on the bus because it is supposed to be used for diagnostic purposes (ie. just in the lab or garage setting). When you plug anything into the OBDII port, that device just became more important that the computer that controls vehicle stability, your airbags, your ABS, etc. ***** was meeting with the heads of these insurance companies to urge them to NOT offer those devices to the public because it has the chance to make their cars LESS safe and cause performance issues. In talking with him, the summary was “don’t leave things plugged into your OBDII port, or you risk messing up your car.” So…now I no longer drive around with my scanner plugged in.
I've had a very sporadic issue, warning lights going on relating to braking system, and the car going into default mode. The dealership has yet to find anything. When it happens and I bring it in, I've always disconnected the ScanGuage that I use constantly. My lastest contact with them: the service manager said it might be purely a communication issue. So might be something there, not sure.
I know the Elantra did not like having something plugged into the port. Iirc brake warning also. Haven't tried driving the volt with anything plugged in. On the other hand the 07 Silverado went 300k with one and sometimes 2 gauges plugged into the port. And my 12 express van has the scan guage for about 20,000 miles now with no issues
This is 100% FALSE and I can't believe an engineer said this. The diagnostic requests are the LOWEST priority of any bus traffic and can be ignored completely. For an 11-bit CAN message, the absolute lowest priority message would have an ID of 7FFh. The priority is inverse to the message ID value. Typically a scangauge request is at 7E0h or 7E1h or the like. In an Escape Hybrid, critical messages have IDs in the 01xh range. Even a slow message that simply broadcasts the VIN has an ID of 540h, much higher priority than a scan tool diagnostic request.
What devices you plug into your OBDII port to get a discount? I can't imagine calling my insurance company and asking for a discount because I have a scangauge I. This whole thing sounds suspect.
This is the input I was looking for and can hopefully trust, since I am dependent on others knowledge on subjects like this. The priority of information in the bus traffic is what seems to me to be critical here, not to jeopardize safety when using the car. Quirks that may show up aren't the real issue. Where is Chris, I'm sure he has some very useful information.
