I’m attempting to perform a TCU calibration on a Deere 750c Series 2 (SN #883922) which has the left track running faster than the right. I’m following the procedure from TM1588 for software 700 or higher, which this dozer has. During the second step (Calibrate Decelerator Sensor (B9) and Engine Speed) the 4E comes on solid and never flashes. The 4 will go away at fast idle, but the E remains. When lowering the engine speed back to slow idle 267 never appears. Is another step required for the Calibrate Transmission Speed Control Sensor or Switch (Step 3)? If it matters, when the hand throttle is pushed all the way forward the decelerator pedal has no available movement (ie. the engine doesn’t drop another 100 rpm). Any assistance is appreciated!
The "E" remains if there is an engine speed issue, either an adjustment or something is amiss with the speed sensor/speed ring. First, make sure the decel pedal is adjusted properly and is within all voltage specifications. Then make sure the actual engine rpm's are in the middle of their specs, both at low idle (both positions of the decel) and at fast idle. Then try the calibration again.
Thank you for the quick reply! I’ll start on that next.
Update: Still getting hung up with the E not going away…only the 4 goes away…when doing the TCU calibration. Since the troubleshooting procedure (9015-20-23) indicates the Hydrostatic Pump Speed has not been met I completed the Hydrostatic Pump Speed Sensor Adjustment (9026-25-27). For one time the E went away and went to displaying 2467 (not sure why it wasn’t just 267). I made it through the left and right calibration without issue. After going through the forward and reverse a Lr stayed on the screen. After shutting the machine down and starting back up the E was again not going away on the TCU calibration (tried multiple times, being very careful to increase the rpm slowl). I went through the diagnostic for the Hydrostatic Pump Speed Sensor (9015-20-36) and all three voltage checks passed. I should note although the procedure starts with using the Deaccelerator pedal, I have been using the center brake pedal for the TCU calibration as no travel left on the decel pedal when the throttle level is in the idle position. I assume that isn’t my issue as the 4 disappears when it should, indicating the decel sensor calibration is successful. I also completed the engine speed adjustments with a handheld tachometer (1910-20-4). Since this machine has the higher serial number the procedure appears to indicate that the idle rpm should be 900 + 25 - 0 rpm And not lower another 100 rpm it’s the decal pedal is pushed to the stop. @mg2361 When you suggested the checking the adjustment on the decal pedal are you referring to the right pedal or the center brake pedal? When the hand throttle lever is in the idle the right decal pedal is against the stop. Should there be a little more travel in the pedal at this point (which would lower the rpm further)? Once the pedal is confirmed I can check the voltages and adjustment. Thanks!
The right pedal. Did you calibrate the engine controller after any throttle/voltage adjustments?
Okay, I‘ll start on the right pedal. Should it have some additional travel downward after the hand throttle is in the idle position against the lever stop bolt? Ours does not, so step 2 of the TCU calibration procedure doesn’t seem possible as the right decal pedal is already at the pedal stop bolt. This is why I was using the center pedal for the procedure. I did not. That only showed up in TM1588 for the 850C so I assumed the 750C didn’t have an electronic engine controller. Is there a procedure to calibrate the 750C engine control?
My apologies, no. While your post said 750, my mind was reading 850 . I do not think the 750 higher serial has extra downward travel. Just make sure the decel sensor voltages are correct. Does your machine have any codes, active or stored? Check your messages. I sent you some information to look at. Might help, might not.
No worries. I have confirmed all three voltages on right decelerator pedal are within range. The machine doesn’t have any active codes. There were some stored when we first started working on this problem. I’ll confirm if they are still there or if we cleared them. I picked up a speed sensor since we will likely need one at some point in the future. Swapping that out for the Hydrostatic Pump Speed sensor did not address the problem with the E remaining. My next step is to inspect the wiring for issues. The service manual references checking the speed ring with a screw driver. When I remove the Hydrostatic Pump Speed sensor oil comes out with some pressure. Is this expected? How do you inspect the speed ring given this situation?
Place a vacuum on the hydrostatic reservoir.
Here are the codes that were stored in order: F629 (Mistracking) — B15 Left Track Motor Speed Sensor Circuit F619 (Return to Neutral Light) Park Lock Lever Circuit Open F653 (1/2 mph) — Neutral Start Switch Circuit F906 Coolant temp. sensor circuit open F904 Engine oil pressure sensor circuit open F640 (Transmission Shutdown) — B14 Hydrostatic Pump Speed Sensor Circuit
I found some exposed wires but none for the hydrostatic pump speed sensor circuit. I checked continuity from the sensor connector all the way to the controller connector. Each of the three wires had zero ohms. Thanks for the tip on pulling vacuum. Do you do this with a handheld pump or your A/C vac unit?
I use the Milton vacuum tool shown below, however they no longer make it. There are many similar items on Amazon and elsewhere available.
Resolution: JD technican had to adjust the idle speed to get past the E in the TCU calibration. Special thank you to @mg2361 for all the support in answering my questions!
I have a 750C i replaced the transmission controller it has a 600 software but now I am getting a f680 code but I don't have the procedure to calibrate the controller
F680 is a missing or incorrect machine identity plug. Has any repairs been performed, or did this code just show up? Will need the machine's serial number for the calibration procedure.