If I were you, I would start with a new K-40 relay. As for the sensors, there is a black sensor that is attached to a small vacuum hose coming off the intake manifold. There is the Throttle Position Sensor. Then, there are two other vacuum sensors that are attached to the air intake filter box. They are both the same part number, one controls the egr valve, the other the resonance flaps. I am sure there are more that I haven't mentioned, but my first course of action after eliminating the K-40 relay would be to disconnect the electrical connector to each sensor, and spray it with an electronic contact cleaner, which can be picked up at Radio Shack. I had an issue this past summer where I got a code for the Throttle Position Sensor.......no driving issues, but still a code. Checked all the vacuum lines, no problems, then went on to clean all the electrical connectors to the various sensors, and presto.....code was reset, and has not returned. This route is not expensive, but does take a little time and effort to complete. Wish you luck in finding an answer to your problem.

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96 E300d