Hi again. Looking at my post I think I may have not explained myself too clearly. I didn't actually do any tests on the MAF itself. I tested the harness to find the live and ground terminals. It was disconnected from the MAF. As said looking at the disconnected plug face on ( IE looking at the pins ) the right pin showed up as positive but the centre and left pins both beeped when connected to the right hand live pin.. Does this alter your views please.
Testing the way that you did can cause you problems.
It sounds like you connected a 12v+ pin and an Earth pin through the Resistance setting on your ohmmeter. This could kill your ohmmeter. This test should be done on the 0-20vDC Voltage setting.
The only tests that you can do with your ohmmeter and the open cable are a test for 12v on the live pin and a test for earth on the earth pin. You can also do a continuity test on the signal pin, but you need access to the pin going into the control module.
All of these tests are flawed, as a single strand of wire would allow the test to "pass", even though the wire is close to failure.
The correct way to test is with a low wattage test bulb (like a dashlight bulb).
Connect one end of the test bulb to the 12v+ on the cable and the other to the earth pin on the cable. If the bulb lights, then both wires are good. If the bulb doesn't light, disconnect the earth pin and connect the test bulb to a good earth on the car. If the bulb lights the 12v+ is good and the earth wire is probably faulty. Confirm this by connecting the test bulb to the earth pin and a known good 12v+ supply (the jump point is a good supply).
Assuming all has passed, the only way to test the signal wire is to test for continuity between the ECU and the plug - (THIS MUST BE DONE WITH THE ECU PLUG DISCONNECTED). 12v+ --> Test Bulb --> MAF Plug Signal Wire --> ECU Signal Wire Connector --> Good Earth = Bulb Lights
The last test is a last resort, as the Blow test should have been done first. You can do a Blow Test on the car (with everything connected), but you have to be very careful...
Set the Voltmeter to DC VOLTAGE.
Use a pin or needle to carefully pierce the signal wire in the loom near the MAF.
Connect one of the voltmeter cable to the pin (or needle)
Connect the other voltmeter cable to a known good earth.
Confirm you are on the VOLTAGE setting - THIS IS VERY IMPORTANT as the resistance (beep test) setting uses the internal battery to power the ohmmeter, and this battery together with the car battery may supply too much power into the ECU.
Start the car.
If the signal voltage changes when you rev the engine, the MAF is working.
What you don't know is whether it is working properly. If it has a dirty "hot wire", then the voltage changes will be smaller than they should be, as the wire is being insulated by the dirt, and isn't cooling down as quickly as it should. This is where
@NZ00Z3 and the software would really help, as this would show if the readings are out of spec. His software would also show if the ECU is working as expected.
In short, plug in the computer
