We have a small bulldozer, s/n T0450JX139324, that we were using to clear fences with and the operator told me he had a problem. The dozer starts fine, but wont idle up, hence it wont move. Blade works fine. Error codes on dash screen: F423 and F9C3. The TCU also has codes flashing on it: RTOS and !APP I have checked fuses and relays, disconnected cables from TCU, cleaned and replaced, disconnected ground strap, cleaned and replaced. All fluid levels are where they should be. I would like to take the throttle dial out of its bracket and check voltages, but the screws are rusted in place that I am sure they would all be destroyed before they came out. Any help would be greatly appreciated.
The (2) transmission codes don’t look familiar. @mg2361 could likely help sort your issue out.
Awesome. How would I get in touch with @mg2361 ?
You did. Using @ in front of a person's username notifies the individual. Welcome to HEF Msh2 ! F423 - Throttle command not received F9C3 - Monitor is not receiving a "CAN" message from the TCU Do you know how to clear the codes? Press and hold the menu button until SERVICE MENU appears in the screen. Then scroll to codes. You will have the option to clear them. Clear them and then let's see if they both come back or just the throttle comes back. Can you navigate the TCU menu structure? The F9C3, if active, may be an issue here. Throttle voltage in the TCU diagnostic section (labeled ThrL and ThrH) should read 2.96 - 4.15 volts at low idle, and 0.45 - 1.22 at high idle. Throttle dial specification (in ohms) measured between pins A and B are: Low idle position: 152 - 200 ohms High idle position: 800 - 848 ohms
Thank you so much. Cant wait to try this. I have cleared the codes on the TCU before but not the dash monitor. Just ran across instructions in a service or operators manual that told me how to do that. The TCU seems to be completely unresponsive. Just showing those two codes back and forth. I don't know where pins A and B are. There are a couple of wire bundles coming from the TCU that are terminated in plastic - one round like a can for a roll of film with five wires, and the other is triangular with three wires. Is this where I need to measure?
This would be at the throttle dial itself. Then that is why you have no throttle response. The throttle dial and the decelerator are connected to the TCU. Then the TCU sends the message to the ECU. Then the ECU controls the rpm's. The voltage supply and grounds need to be checked at the TCU to make sure there is not an issue here. Check wiring as well for rodent damage. Check all the fuses. I'll send you a TCU wiring diagram later when I have time. Probably in the morning. Look for it in your messages.
I’ve cleared all the diag codes from the monitor display, turned key off and then restarted engine. The only codes left were F9C3 and F423. The TCU display was unresponsive. I pressed and held each of the buttons on the unit and could get no response. It just kept flashing RTOS and !APP.
Thank you. Just got your message. All the fuses are good. Grounding strap has been removed and polished.
Throttle dial measurement were 350 ohms at low idle and 650 ohms at high idle.
I copied these from a post in October by @mg2361 . I am trying to verify my voltages but can’t figure out where to take the readings. If I disconnect the cables from the Tcu then I lose my voltage. Unless I read the voltage on the unit but then I lose signal from decel. Decel pedal voltages should be: Up position: 1.40 - 1.55 volts Low position (when resistance is felt): 3.40 - 3.60 volts Brake position (all the way down): 3.79 - 3.99 volts
Possibly I am taking these instructions out of context. These values are for recalibration and would possibly show up as voltages on the TCU screen.
A little more testing on decel - I unplugged the wiring harness from the TCU and measured resistance across the pins and got no changes as I moved the brake pedal up and down.
I hope it doesn’t come to it but before you replace the TCU, watch this video. These guys do more work on Deere J dozers than any other type. They are a wealth of knowledge.
You can do all the throttle testing you want, it means nothing if the screen in the TCU is unresponsive and never makes it to the screen that says PARK..