RoverGauge Diagnostic port wiring

[ez64]

After trying to use RoverGauge to diagnose a high idle\misfire issue which started after snapping the stepper motor and replacing with a range rover unit I could not get past the red connectivity light even though no failure is presented on selecting connect.


While going to do the resistance tests on the port wiring I found someone has been handy with the scissors and soldering iron.

My question is what should the wiring for the plug look like from the factory (I know that could depend on the bloke that was wiring my car that week but any pointers appreciated)





For a bonus question any idea what this little blue resistor is for?

Edited by ez64 on Tuesday 12th May 17:34

[Belle427]

That’s odd, looks like a shorting link which isn’t normally there. No idea why you would do that.
That’s a tune resistor, selects the correct tune in the ecu.

[Steve_D]

Whatever that is it should not be there. What is in the plastic joint? is it just a connector or is it something like a resistor or a diode?

As said, the other jobbie is a tune resistor. The ECU has several maps installed. The value of the tune resistor determines which map is used.

Steve

[blitzracing]

I think I can see whats been done. There can be a loopback plug in the OBD socket that grounds the receive signal from the ECU to prevent noise in the input. It looks like a shorting link has been put in there as the loop back plug is missing. Most TVRs Ive seen dont have the loop back installed and Ive yet to see the ECU throw a wobbly without it. You can simply unplug or remove the extra connection and be done with it. My only minor concern is if it will have damaged the RoverGauge cable as its effectively grounded the Tx side of the cable. You can always check the cable with the simple loopback test in the RG installation notes.

[ez64]

Thanks for the help guys. I've removed it and all is working in RoverGauge so luckily it does not look like it damaged the cable.

I think the "high idle" is actually the TPS or wiring as the position value is 14%. (The cable is slack as well so the butterfly is physically in the closed position)

I believe the o2 sensors should not be showing 100% fuel trim either on short term suggesting they need new wiring\sensors.

[blitzracing]

If you can get the probes out, just swap them over and see if the fault moves sides, that will indicate a dead probe or missing heater voltage.

[Steve_D]

The Lambda probes will be missing their power supply if the wrong type of relay has been used at the fuel pump relay.

Steve