Intermittent codes can be time-consuming and frustrating to track down. Sometimes a sensor can fail while driving, typically from heat buildup, and the computer can still run the engine on a second sensor. What you see as the "Top Dead Center" sensor is commonly referred to as the crankshaft position sensor. The other one the computer uses is the camshaft position sensor. Some cars require good signals from both sensors for the engine to run. Some cars only require good signals from both to start, then it can stay running if one fails but it won't restart after turning the engine off. Some engines can always start and run on just one sensor but in a reduced power mode.
Those are three possibilities of why you could be getting that code but the engine still runs. Think of it as having a flat tire but there's no need to get it fixed because you have the spare tire to drive on. You might get by okay, ... Until another tire goes flat.
If your mechanic's test results are to be believed, 12,000 ohms is way too high for the TDC sensor but it's rare for the value to go up without being completely open, as in a broken wire, because there is nothing that can cause that to happen. The reason I sound like I don't trust your mechanic is because after repairing tvs and vcrs for 35 years, and cars for 25 years, as a professional, I have gotten incorrect results WAY too many times to count and they have sent me down the wrong diagnostic path. That happens to all of us many times. It's not the mechanic I don't trust; it's the readings. When I DO finally find the cause of a problem by the meter reading, I find it so hard to believe that I scratch the probes to make better contact multiple times, and poke and wiggle to be sure my reading is correct.
What it boils down to is I hate to see you spend money needlessly on a part that isn't needed, but it would be worse to have a second sensor fail and leave you stranded on the side of the road. If the light doesn't come on for another month each time that sensor is tested, you might look closer at the connector itself to see if there's a light film of corrosion on the terminals. If there is, the scratching action of reconnecting the plug can scratch through that corrosion and make a good connection for a little while. Cleaning the terminals is the solution for that.
Tuesday, July 10th, 2012 AT 6:04 PM