Honda ATV Forum banner

1 - 20 of 32 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter #1
Hello. I just joined to forum and am in need of some advice with my rancher. I've been working on a TRX350FE2 that didn't run without dumping gas and wouldn't shift. I rebuild the carb and now it runs well but I've run into some issues with the electric shift. I don't know much about the systems but here's what I have done so far...

First I traced all the wires to and from the button switches, motor, angle sensor and ecu. All have continuity and the buttons both work.

I tested the angle sensor with my multi meter and when I move the shaft the resistance changes evenly. I can't remember what it read exactly but I believe it is good. When I unplug the angle sensor the atv still knows what gear it is in so I assume there is another sensor for gear position. I also assume this would be working because it reads out all the correct gears when I shift manually. However, I have seen another poster on this forum that had similar symptoms and the gear position switch was his cure.

There is no voltage going to the motor when I push the buttons and it doesn't even budge, but it does spin if I run a jump straight to the battery. This leads me to believe the issue is at the ecu. I cleaned all the contacts to on the ecu and none of the pins are bent or missing. All other functions work on the atv except I haven't seen the fan come on yet (I think it requires a certain oil temperature).

So I'm kind of at a loss as to what the problem could be. I understand that it's the ECU that is shutting down the process because something is wrong. Any and all help would be greatly appreciated. Thank you!
 

·
Registered
Joined
·
108 Posts
It is the ECU. It is best to bypass it, because something else could be wrong too. Like the regulator may have fried it, or maybe another wire is not making good contact.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #3
It is the ECU. It is best to bypass it, because something else could be wrong too. Like the regulator may have fried it, or maybe another wire is not making good contact.
I figured. I'm not opposed to buying a new one or seeing if I can salvage one given that I have some money to spend on this project. Can you direct me to a method of bypassing it?
 

·
Registered
Joined
·
15 Posts
Discussion Starter #4
It is the ECU. It is best to bypass it, because something else could be wrong too. Like the regulator may have fried it, or maybe another wire is not making good contact.
Just another thought... if there was an issue with the ecu, wouldn’t I be getting an error on the screen? Something like a blinking number or “- -“
 

·
Registered
Joined
·
15 Posts
Discussion Starter #5
I'm considering buying this part. I wired a bypass around the change control unit and It shifts with no problems other than I have to flip the wires to get it to downshift or vice versa. I'd take the time to wire a more sophisticated bypass but since I plan on selling it when I'm done, I might as well fix it right.

Does a new ecu seem to be the correct fix based on my symptoms?

Honda 38910-HN5-A11 - CONTROL UNIT, CHANGE | Partzilla.com
 

·
Registered
Joined
·
108 Posts
Bubba Baryl has a youtube video about bypassing the ECU. The older Hondas will not flash a diagnostic code. Replacing the ECU may not fix the problem because it could be a corroded connector.
 

·
Super Moderator
Joined
·
37,577 Posts
Bubba Baryl has a youtube video about bypassing the ECU. The older Hondas will not flash a diagnostic code. Replacing the ECU may not fix the problem because it could be a corroded connector.
why would you tell a member to bypass a part ?, and why not just check/clean the connectors ??. your not making any sense at all !.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #8
why would you tell a member to bypass a part ?, and why not just check/clean the connectors ??. your not making any sense at all !.
I have checked and cleaned all connections and confirmed that all sensors have continuity to the ecu. I get a constant 7.82 volts to the motor but no change when I push the shift buttons. I did the bypass just to test the gear positions indicator and the shift motor, not a permanent fix at all. I'm still leaning towards it being the ecu but I'll test everything again just to be sure.
 

·
Registered
Joined
·
8 Posts
Check the reverse position sensor (I believe that's what it's called). It is often overlooked because it is on the back of the engine and hard to see. This was what was causing all kinds of havoc for me, causing all types of no shift issues. I lucked out and had a dealer let me borrow an ECU, but it didn't make any difference. The sensor is about $15 and I haven't had any issues since. And I had swapped/cleaned/tested EVERYTHING!

Hope this helps!
 

·
Registered
Joined
·
108 Posts
The 7.82V at the shift motor indicates the mosfet switches in the ecu are fried.
Whatever you decide to do, do not convert it to a foot shift. Foot shift models are for old timers who can't figure out what the buttons are for.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #11
The 7.82V at the shift motor indicates the mosfet switches in the ecu are fried.
Whatever you decide to do, do not convert it to a foot shift. Foot shift models are for old timers who can't figure out what the buttons are for.
I thought the same thing. My guess is that it should be 0v and then 12v when a button is pushed.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #12
Check the reverse position sensor (I believe that's what it's called). It is often overlooked because it is on the back of the engine and hard to see. This was what was causing all kinds of havoc for me, causing all types of no shift issues. I lucked out and had a dealer let me borrow an ECU, but it didn't make any difference. The sensor is about $15 and I haven't had any issues since. And I had swapped/cleaned/tested EVERYTHING!

Hope this helps!
What is the best way to test it? Check to see if it sends a signal when in reverse?
 

·
Registered
Joined
·
8 Posts
What is the best way to test it? Check to see if it sends a signal when in reverse?
That is probably the proper way to do it. I was at my wit's end, so no more than the part was I just bought it and replaced it.

ALSO worth mentioning... The connector on this particular switch... It just pushes on, so a stick can easily get up there and knock it off or mess it up. I'll try and get a pic.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #14
That is probably the proper way to do it. I was at my wit's end, so no more than the part was I just bought it and replaced it.

ALSO worth mentioning... The connector on this particular switch... It just pushes on, so a stick can easily get up there and knock it off or mess it up. I'll try and get a pic.
Okay thank you. I think if I back it up on ramps, I'll be able to get decent access.

Just a quick question... when this switch was giving you issues, were you able to shift into reverse manually?
 

·
Registered
Joined
·
8 Posts
Okay thank you. I think if I back it up on ramps, I'll be able to get decent access.

Just a quick question... when this switch was giving you issues, were you able to shift into reverse manually?
Yes. Manual shifting did not give me a problem. I was getting random error codes flashing on the display. There was no rhyme or reason or consistency. It was aggravating as heck! Since I have replaced this switch I have not had any issues at all (knock on wood). I do think once you get this switch out, you can check it with an ohmmeter for continuity.

just be advised you may lose just a little bit of lubricant when you pull the switch out. If you back it up onto ramps and have the rear end up high you may not lose much at all.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #17
The reverse switch might b
Yes. Manual shifting did not give me a problem. I was getting random error codes flashing on the display. There was no rhyme or reason or consistency. It was aggravating as heck! Since I have replaced this switch I have not had any issues at all (knock on wood). I do think once you get this switch out, you can check it with an ohmmeter for continuity.

just be advised you may lose just a little bit of lubricant when you pull the switch out. If you back it up onto ramps and have the rear end up high you may not lose much at all.
This switch might just be my problem. I tested it for continuity from the switch to itself, to the common on the ECU, and to the negative on the battery and all had no continuity when I pushed it down. Am I testing wrong or does this switch appear to be bad?
 

·
Registered
Joined
·
21 Posts
The switch in that photo looks like the oil temp sensor, not the one for reverse. I thought the reverse switch was part of the gear position which is under the rear cover. Or do I have this mixed up?
 

·
Registered
Joined
·
15 Posts
Discussion Starter #19
The switch in that photo looks like the oil temp sensor, not the one for reverse. I thought the reverse switch was part of the gear position which is under the rear cover. Or do I have this mixed up?
I think oil temp is on the side by the manual gear change. I tested it as well and could get the fan to turn on when I jumped it.
 

·
Registered
Joined
·
21 Posts
OK, gotcha. The parts breakdown shows the rear cover having a neutral switch that looks similar. Could be a typo since the service manual mentions a reverse switch that's separate from the gear position switch in that spot. Are you getting a reverse light display on the gauge at all?
 
1 - 20 of 32 Posts
Top