I work in an outdoor equipment store. We have a tym tractor with a tcd 2.9 motor in the shop that has been giving us problems for a month now. Basically the unit came in with a surging issue and check engine light. Tried to read codes but tractor would not connect to Serdia. After some extensive diagnostics found that can 1 line did not have proper resistance and replaced engine harness. Now we can talk to computer. Code that it is setting fuel pressure data above operating range. Basically rail pressure is about double the pressure that it should be and at times it does open pressure relief valve. So tym has been very little help diagnosing this problem. My thoughts are the mprop is bad but they provide very little insight into this. The mprop has an ohm reading of 2.5. Manual states it should have 3. I tested a known good mprop and it had 3.0-3.1 ohms. Is this mprop that fussy with a resistance reading? I checked voltage with both sensors unplugged and the results were nearly identical. Any ideas? Seen before? Anything else I should be looking at?