Hi, I just purchased an L5740HSTC-3 with 1900hrs on it that the previous owner wasn't interested in trying to figure out. I was in need of a 50ish hp tractor for my small farm and the tractor was priced that even if I can't fix it, I can part it out or possibly even purchase a similar model and just keep this one for parts. I've confirmed the engine is ok, we pulled the stop solenoid and jumped the solenoid to the starter, the engine popped off right away, this made moving the tractor easier since we could move the loader and it made steering easier. I apologize for the lengthy post below, I'm just trying to give as much information as I can up front with regards to what I've tried so far. I will bold my actual questions.
When you try to start the tractor normally it throws an ERROR-20 code on the panel. I've purchased the WSM for the tractor it says this is a communication error between the ECU and the electronic instrument panel and the first step is to check the fuses, I assumed this is referencing fuse the 5amp T/M controller 1 and the 10amp T/M controller 2, both of these fuses are good and so are all the rest of the fuses. The next step is to Check the ECU connector, I pulled it and checked the connector and pins on the ECU for damage/corrosion/contamination, all looked good, there was a nice amount of dielectric grease in the connector. The next step was to check the communication line between the ECU and instrument panel at the ecu connector. This step is where I run into my first question, it has you check for voltage at the connector, I pulled the connector off of the ECU, turned the tractor on. I has you check for 12 volts across terminal 23 to 29, this tested out good. Next it has you test across terminal 30 and 31, you're supposed to get 5v, I got nothing. My question is are you supposed to perform this test when the connector is connected to the ECU via the back of the connector? I ask this because looking at the wiring diagram I couldn't figure out where the 5volts supply was except that the ECU produces it... to check this, I pulled the connector on the back of the HST Mode select/response control and found I had 0 volts on the terminals that should be connected to this same 5v circuit, however when I plugged the ECU back in and turned the tractor on, I had 5v across those terminals? Does the ECU generate the 5v for the sensor circuit? If so I believe the test I performed shows that the 5v circuit is live. After checking the voltage at the ECU connector it has you test the continuity between the ECU connector and connector b of the panel connector, this test was good. Those are all the tests it provides in the WSM to check the ECU. Am I to assume that if I've performed these tests the ECU needs to be replaced? Would a dealer be able to bench test the ECU to confirm it is bad? I did also use the panel to run the test mode and found there was no readings on T5-T16, all the sensors that the ECU manages, presumably because the ECU is not communicating because it has failed?... I tried to utilize mode "N" (Tractor Model Select Mode) and after selecting N it says "ECU SET" and when you press/hold the display mode switch it never goes to the "ECU-ADJ" that the book says it should... I just tried this because the book notes that if a new ECU is installed this needs to be done first, I didn't know if perhaps the previous owner had swapped it out and never set this and if not setting the ECU up could cause it to produce this error?
I'm hoping someone more experienced with troubleshooting these machines is able to give me some guidance, thank you in advance, and I look forward to being part of the community.
When you try to start the tractor normally it throws an ERROR-20 code on the panel. I've purchased the WSM for the tractor it says this is a communication error between the ECU and the electronic instrument panel and the first step is to check the fuses, I assumed this is referencing fuse the 5amp T/M controller 1 and the 10amp T/M controller 2, both of these fuses are good and so are all the rest of the fuses. The next step is to Check the ECU connector, I pulled it and checked the connector and pins on the ECU for damage/corrosion/contamination, all looked good, there was a nice amount of dielectric grease in the connector. The next step was to check the communication line between the ECU and instrument panel at the ecu connector. This step is where I run into my first question, it has you check for voltage at the connector, I pulled the connector off of the ECU, turned the tractor on. I has you check for 12 volts across terminal 23 to 29, this tested out good. Next it has you test across terminal 30 and 31, you're supposed to get 5v, I got nothing. My question is are you supposed to perform this test when the connector is connected to the ECU via the back of the connector? I ask this because looking at the wiring diagram I couldn't figure out where the 5volts supply was except that the ECU produces it... to check this, I pulled the connector on the back of the HST Mode select/response control and found I had 0 volts on the terminals that should be connected to this same 5v circuit, however when I plugged the ECU back in and turned the tractor on, I had 5v across those terminals? Does the ECU generate the 5v for the sensor circuit? If so I believe the test I performed shows that the 5v circuit is live. After checking the voltage at the ECU connector it has you test the continuity between the ECU connector and connector b of the panel connector, this test was good. Those are all the tests it provides in the WSM to check the ECU. Am I to assume that if I've performed these tests the ECU needs to be replaced? Would a dealer be able to bench test the ECU to confirm it is bad? I did also use the panel to run the test mode and found there was no readings on T5-T16, all the sensors that the ECU manages, presumably because the ECU is not communicating because it has failed?... I tried to utilize mode "N" (Tractor Model Select Mode) and after selecting N it says "ECU SET" and when you press/hold the display mode switch it never goes to the "ECU-ADJ" that the book says it should... I just tried this because the book notes that if a new ECU is installed this needs to be done first, I didn't know if perhaps the previous owner had swapped it out and never set this and if not setting the ECU up could cause it to produce this error?
I'm hoping someone more experienced with troubleshooting these machines is able to give me some guidance, thank you in advance, and I look forward to being part of the community.
