Any suggestions on what this might be. I have a obd2link and the rev app on my itouch works via wifi works awesome on my other cars but on the rover the data comes then goes its not steady. could it be a short or something?

 

Probably something else. OBDII port just has power and one data, could be any module disturbing it, but then codes would result. Can your software handle the multiple ECU modules? See attached, or download the whole RAVE for your reading enjoyment.

 

Same thing happens with my scan gauge.

 

Our Discos have two ECUs (transmission under the drivers seat and engine behind the glove box)...

If your OBD app/tool can't handle two ECUs, or shows two ECUs when you're only expecting one, or sees two ECUs but only shows you one and intermittantly switches between showing you data from each, etc etc.... Things can get confusing etc...

Cheers,

Thomas

 

If you look at the wiring diagram posted above from the RAVE, there are like seven "electronic control units" that talk to the OBDII port. Tranny, ABS, Body Control Unit, etc. Only very sophisticated equipment can handle all of these, and how a less sophisticated reader reponds when it encounters codes of another "language" or out-of-known range of possibilities is a programmer issue for that builder of reader. Getting two programmers to agree on anything other than the need for a raise is difficult.

 

Savannah Buzz,
I'm clarifying my response for the benefit of forum members who may not be as familiar with this topic as you and I are....

This is of course 100% correct.
I could have been clearer, but I was referring to the fact that almost all consumer/generic OBD readers and scanners only access data that can come from an Engine ECU and a Transmission ECU.

It's my understanding that in a vast majority of domestic and japanese vehicles, the engine and transmission ECUs are in the same computer module and are a single unit. Ergo, my response about possible confusion when finding 2 modules when expecting only one etc.....

Yes, but generally speaking an ECU will ignore and not respond to anything it doesn't recognize or understand, PID/"language", it recieves from an OBD reader/scanner.
As you say, what the OBD reader/scanner requests from an ECU, and what it does with the data it recieves from an ECU, is dependent on the reader/scanner builder's programmers etc. This is often dependent on the programmers understanding of how individual auto manufacturers have implemented OBD (beyond what is standard for emissions testing) etc. These programmers know more about GM and Honda OBD/PIDs than they do Land Rover etc. As a result, when a generic OBD scanner encounters an engine fault code that is Land Rover specific, it might only be able to give you an engine fault code number and refer you to Land Rover for more info etc.

Cheers,

Thomas

 

And to add to the mix, many D2 use Bosch engine management, kinda like some other Euro cars. Just with that muddy oval flavor. I believe the programmer term is "nailing jelly to a tree" that covers keeping up with all the potential changes.