Error-20 L3940

[Tinman6464]

Error-20 L3940/update

L3940, error-20 . Had a stick break speed sensor on right side of trans, replaced, hold down travel speed and display mode buttons while turning key on, brings up menu to clear code .... done ...... error code comes back tractor wont start..... checked wiring, have continuity on 2 of the wires to ECU black w/white stripe and orange, red w/2 white stripes no cont. Same wire goes to shifter and another sensor I think on top of trans one at shifter has cont other does not ...... when I clear code it says clear I push and hold disp/mode button it says "push sw" I do it says "ok"
I'm lost help please anyone tractor is stuck on a job for a wk and have work with deadline

UPDATE; I've gotten a shop manual and done all the diagnostics, everything cks out except red w/2 white stripes (power) to sensor no power, manual says " ok if has 0.5 volts ... But doesn't say if it has no voltage what to do.....
I tried the emergency connector which I assume is for this type situation, it still won't start still says error-20
I narrowed it down to the ECU got a new one $873 plus shipping it wasn't the ECU SOMEONE PLEASE HELP ME

 

[200mph]

This is what I found in the workshop manual. Hopefully it will be of value to you. Please report back what you find and your solution so others can learn form it or reference later.

Good luck!


If any of the following troubles occurs, its related
error code gets displayed flashing in the panel's LCD
screen as shown in figure. With the repair finished, the
error code disappears. The error information will be,
however, put in the memory device of the electronic
instrument panel and can be reviewed in the Error
Information Display Mode (Refer to "4. CHECKING AND
ADJUSTING" of "SERVICING" in this section). Such
error information can also be deleted out of the error
history by operating of Error Information Reset Mode
(Refer to "4. CHECKING AND ADJUSTING" of
"SERVICING" in this section).

Display on LCD Screen: Error-20

Trouble Item: Communication error between ECU and electronic instrument panel

Problem Cause:
• Fuse blown out
• Communication line between ECU and electronic instrument
panel is broken or short-circuited
• No signals from ECU for longer than 5 seconds (error cleared if signal sent
and received later)
• ECU damaged

Solution / Reference Page
Check the fuse 9-S35
Check ECU connector 9-S45
Check the communication line between ECU and electronic instrument panel at ECU connector 9-S39, 9-S45
Replace ECU 9-S45

 

[Tinman6464]

200mph do you know if there is s way to test ECU ? IM THINKING ITS MY PROBLEM I've checked all fuses and connections and it started when speed sensor broke wires must've shorted and fried it I hate to go buy one without testing it first

 

[200mph]

I don't know off hand and don't have the time to investigate further at this time (sorry).

It's probably in your best interest to invest in the WSM (work shop manual) at this point. They update these on occasion and you would be assured they have the latest.

It might be possible for the dealer to bench check the ECU. This would prevent having to go through the hassle of transporting tractor and it would shift the burden of proving it is bad on them.

 

[Tinman6464]

Yeah wish I would've already gotten one I will be for sure .... and thank you for the time you've taken to help I really appreciate it alot

 

[200mph]

Tinman6464,

Did you ever resolve your problem(s)?

Curious what the fix was.

 

[200mph]

Tinman6464,

Any resolution to your problem?

Care to comment on the fix?