My truck has gotten a P0217 (Coolant Temperature Too High) & P2121 (Pedal Position Sensor 1 Performance / Rationality) code for the second time within the past week. Each time the check engine light comes on & the truck went into limp mode. The instrument temp gage was just under 200 degrees & the engine felt very cool to the touch (could hold onto upper radiator hose, put a finger on the exhaust manifold & keep it there for 1 second, etc.).

The second time it happened I pulled over right away to pop the hood & see if the engine felt hot. Felt cool, so went back on the road (still in limp mode) & drove for 15 miles (and still in limp mode). Pulled off the road & let engine idle for 5 minutes, then shut it down for 10 minutes. Went back on the road & no more limp mode, but check engine light was on. After 3 key cycles (off/on/off & pulled key out) the check engine light went off.

Now, last week I did a coolant flush, so when this happend the first time, I figured that I had an air pocket. But, I put on 750 miles between the first time & second time that this happened, so I don't think that it is an air pocket any more.

How can I check if I have a bad sensor or if the engine is overheating? Also, where is the sensor for the P0217 gage & the instrument gage? They can't be picking up off the same sensor.

Any suggestions?