Despite the numerous forums about glow plugs, I'm still having a hard time diagnosing the problem.
Here's the summary:
v 1 year ago check engine light with emissions workshop appeared
v Stealership advised me to replace the wiring harness for the glowplugs.
v I did nothing, check engine disappeared (probably loose connection or corrosion)
v Recently check engine light and emissions workshop light re-appeared
Ø Tested all 4 plugs with Ohms meter – they’re all good
Ø Read SEVERAL forums and decided to unplug the temperature sensor to test the glow plug relay:
§ Unplugged sensor located near the radiator on the driver side
1. Is this the right sensor to unplug?
2. Turned the car to the on position, Voltmeter read approx 2 volts. Using a different wire for another glow plug I tried the test again – 2 volts.
3. Therefore, either the test is flawed or the relay is pooched?
4. How should I proceed?

I’ve been on this for a while now. Anyone have words of wisdom; I would be very grateful.