I have been getting an intermittent coolant temp sensor check engine light for the last year and a half or so. I've changed the sensor, first with an aftermarket unit, and just last week with a sensor bought from my local volvo dealer. Still I get the light.

I bought a known good 951 computer to check to see if my computer was dying and causing the problem, but still the light remains.

So this leads me to believe there is something in the wiring that is causing the signal from the sensor for the ecu to fail intermittently. So there a ground associated with the sensor in the wiring that could be corroded and causing it to not ground sufficiently sometimes? Do the two grounds on the intake manifold tie into this system? The connections at the ECU and at the plug for the sensor both look good so I'm kind of at a loss as to why the thing isn't happy. I'd really appreciate some assistance if anyone knows of a cause/solution.

Car is a 1990 240 automatic with LH2.4