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Deere 550H not reading RPM

BMC330 ยท 2026-07-31 20:57

I hope someone can help as I am not sure what to do next. I have code F392 and my machine will not turn. It is not reading RPM at the computer. I have replaced the sensor and still no luck. Can someone point me in the right direction on getting a service manual or give advice on what to do next. I am going to get my ohm meter out in the morning and start testing but I don't have any idea what volts I am looking for or where the wires enter the transmission computer to check the wires. I searched but no luck finding any information to help.

Replies9
  1. #1mg23612026-08-01 06:26

    Let's start with the machine's serial number please. Once we have the serial, I'll get you the correct schematic so you can check out the wiring (most likely issue). In the meanwhile, with the key on, backprobe the wires at the sensor connector carefully (use a pin, not the meter leads) and measure the voltage at each wire. Report the results.

  2. #2BMC3302026-08-01 08:03

    T0550HX889214

  3. #3BMC3302026-08-01 12:35

    Left my OHMS meter at home. Dozer is on the farm. Going to run home and get it or go buy a new one. I will advise my findings as soon as I can.

  4. #4BMC3302026-08-01 12:36

    From the sensor Red wire 5.05 White wire .30 Black wire .05 Green wire .06

  5. #5mg23612026-08-02 06:44

    Which sensor are you looking at? F392 is for the engine speed sensor, which is mounted directly on the hydrostatic pumps and is a 3 wire sensor. Is F392 the only code? Which RPM? Check your messages.

  6. #6BMC3302026-08-02 08:07

    F392 is my only code. I am not reading engine RPM on the computer. Thank you for your help.

  7. #7BMC3302026-08-02 11:29

    I have a 5 volt reference and ground on my sensor. What I'm guessing is my signal wire dose not change from the key on to engine running. Im getting .30 reading the whole time.

  8. #8mg23612026-08-03 05:35

    With the sensor unplugged, what is the voltage measurement of the T21 Blue signal wire (pin B) on the machine harness side connector with the key on? It should be 2.5 volts. If it is still 0 volts, then there may be an open/short to ground in that wire.

  9. #9BMC3302026-08-03 12:28

    I didn't check it unplugged but I will. It may be a couple of days before my next response as the dozer is on my farm and I am working. I hope I don't have to go out of town. Thank you so much for your help.