Chances are good its a gauge issue. To be sure you should hook a mechanical gauge to the engine and try to reproduce the fault.
To install a mechanical guage you'll need an adaptor to install in the sensor port, preferably an adaptor that allows the sensor to be installed at the same time. Dealerships have an adaptor designed to do this test, maybe a local garage will have one and you can borrow theirs or get them to test the system.
To install a mechanical guage you'll need an adaptor to install in the sensor port, preferably an adaptor that allows the sensor to be installed at the same time. Dealerships have an adaptor designed to do this test, maybe a local garage will have one and you can borrow theirs or get them to test the system.