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2002 Trx 350 ES wont shift

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I have a 2002 Honda TRX 350 TE 2WD with electric shift that will not shift.

I have downloaded the Honda service manual and printed out the pages needed.

Following the flowcharts provided by Honda I will discuss the things that I have tried to fix this bike. I’m also communicating with AKATV on this forum for help.

Starting off, the Batt is fully charged and there are no fuses blown. And 12V to all places coming out of the fusebox.

The clutch is properly adjusted.

I can shift the bike manually with the tool to each gear needed. On the display it will show the correct gear position that is selected.

Next test is to check for voltage on the Black/Green wire at the connector at the ECU to ground with the switch turned ON. There is 12V to ground at this wire.

Next test completed was to disconnect the Brown Connector at the ECU. Then measure the voltage  between the Red/Yellow + terminal of the harness and ground – with switch turned on. There was 12V there with switch on or off. Because it comes directly from the Batt/Fuse.

Next test. Is to test between the Green wire at the Brown connector to Ground-.which showed good connectivity to ground-.

Next was to test the resistance at ECU connector for the angle sensor. Which was 4.6ohms.

Next test was to remove the angle sensor and visually inspect. Everything was in perfect condition. Resistance the same there, 4.6ohms. Then checked the input voltage at the angle sensor plug, it was 5V.

Next test is to test the continuity of the gearshift switch which is done at the front connector under the front fenders. The standard voltage form the Black/Red wire is 5.0V as recommended. The continuity between the White Blue wire and the Red/Black when the UP switch is pressed is perfect. The continuity between the White/Yellow wire and the Red/Black is perfect also. These connections were checked at the connector 10P under the fenders and also at the connector at the ECU 22P. all were normal and had 5V going into the switch at 5V. And when backprobed at the ECU connector the 5V would be put to the up/down switch wires, white/blue –black red and white/yellow-black red. So continuity and voltage both to and from the GEARSHIFT SWITCH are all normal.

Next test is to test the GEAR POSITION SWITCH located in the rear housing of the engine by checking continuity between all wires going to that switch from connector 22P the ECU connector and the 8P going from the GEAR POSITION SWITCH  Each terminal needed to be tested to ground at certain gear positions. 

Neutral=light green/red to ground. Good ground.

Reverse=gray to ground. Good also.

1st=white/green to ground. Good ground.

2nd= white/red to ground. Good ground.

3rd=blue to ground. Also good ground.

4th= yellow to ground. Good ground.

5th= light blue/white to ground. Good ground.

Next test is to check continuity  between the 2P connector connecting the Shift motor and the 5P connector at the ECU. All good there too.

Next test is to remove shift motor and bench test by applying 12V directly to the motor.

It ran as smooth as possible. And by reversing the wires would run backwards also.

After that the next step from the service manual is to replace the ECU/change shift unit.

Which I did, and no change to no shift condition.

I have a 2006 Honda TRX 350 Electric Shift also, so I swapped the known good ECU into the 2002. still no shift. So by trying 3 different ECUs it is not that causing the trouble.

I also swapped the angle sensor from the 06 to see if that worked too, still no shift. 

Both part numbers are the same for the ECU and the Angle Sensor for the 2002 and the 2006.

I also installed a new GEAR POSITION SWITCH just to be sure and still no difference.

So I’m stuck with a $380 ecu.

Next I checked the speedometer sensor and cleaned it. Measured voltage between black/blue + and green-. Which produced 5V. and the speedometer registers at the display by turning the tires.

All gear positions are displayed correctly when manually shifted from gear to gear.even reverse. 

Pin fitment has all been checked on every connection by back probing.

The motor runs good and the shift gears have been cleaned up and re greased.Just cant get any voltage to it. 

All fuses and power to red?black are good.


ECU swapped with good/known

Angle sensor swapped with good/known

Shift motor bench tested with 12V good. 

All gears show exactly where they are.

Speed sensor works and displays speed. 

This thing has got me throwing tools!

I need some help. Honda techs around here know nothing.

And wont even work on it.



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@retro, @Melatv, and AKATV are probably the most electrically inclined here on the board.


I don't like it LOL


Thought would be to "follow the voltage"  When you hit the shift button to shift up, for example, you have voltage going through that switch, then through the ECU and to the shift motor, for example?


If you've replaced the ECU (several times) and you have, for example, power going into the ECU and not back out of the ECU to the shift motor, then you'd have a bad connection at the pin/plugs on the ECU or a broken wire between ECU and shift motor.


Might just be blabbering without knowing what I'm talking about, but I've only had a couple of bad ECU's and they were bad fan controls but everything else still worked.  I've had quite a few machines that were throwing codes that pointed to bad ECU's after a lot of troubleshooting and it was always a wire/pin not making a good connection, either at the ECU or elsewhere.


They have an ES bypass kit that would be an option, but sounds like you want to fix it right. 


You have my sympathy.  I hate trying to track down such problems.  Melatv and retro (and AKATV for that matter) seem to love it LOL

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I agree with Jeep to follow the electrical path to first point of failure

I think at this point, as per manual, he is not seeing a failure and will be going thru the manual step by step today

I am THINKING it might be a harness issue if he has swapped all other parts around

We are knee deep into it, for sure, but I feel its something simple being overlooked 

Hard (for me) to trouble shoot without having hands on, as sometimes whats in my mind doesn't come out right.. lol

I too have very seldom had or seen a bad ECU, I think it takes a lot to zap one for good,

 I have found a few pins that pushed back inside the plugs that were not touching etc 

This SEEMS to have started after a starter replacement, but not sure its connected

The young man he is fixing it for had originally pulled shift motor /gears thinking it was the starter-so...





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2 hours ago, AKATV said:

 I have found a few pins that pushed back inside the plugs that were not touching etc 



My guess, or a broken wire somewhere in the harness.

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I didnt get back to working on it today. 
I understand what you guys are saying to follow voltage. While doing the other tests I checked the voltage going into the handlebar switch up/down at the connector going into it. Then while checking connectivity while pushing each switch, between black/red and white/yellow and white blue which proved good. I decided to check to see if voltage was being sent down to the white/yellow white blue wire from the black/red. Which it was. So I connected the ecu and back probed all three. And when the switch was pushed it read the 5v ref on both wires. I will remove the wires and gently squeez the pin connector to be sure it is going into the ecu. 

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