Honda TRX ATV Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1
Hi, I bought a TRX350 2001 last fall. It was initially an ES model but was converted to a manual shift before I bought it and the speedo doesn't work. I bought it cheap and it looks like it had been sitting still outside for a while. I got it in the fall. This winter it was often hard to start but it eventually did and was running, but it would sometimes backfire or stall. My first thought was that it was a carburetor issue, so I rebuilt it.

In the spring, I thought my problem was related to the battery draining and that maybe it wasn't powerful enough to start the engine (I had drained it a few times trying to start it during the winter). Then I noticed that sometime the reverse light would come up while while running in 2nd or 3rd gear, when it did that it stalled within a few minutes and would not start again. Once did that and blew a fuse, I replaced it and it worked again.

A few days later, the red reverse light came back, it stalled and never started again. While trying to diagnose the problem I realized it's not making any sparks. I started looking into the cabling and electronics. I noticed 2 things, 1st when I unplug the small connector of CONTROL UNIT (38910-HN0-A11) the Reverse light shuts down but still no spark. The 2nd, one of the pin (upper left) of small connector of the control unit is broken/missing and there was some moisture/water in it when I unplugged the small cable. This leads me to think that is my issue, but before I go and spend 350-400$ on this part I would like to get some advises.

I was told that this parts rarely fails. If it does fail, could it cause a no spark issues like the ones I'm experiencing? is there a way to bypass the control unit?

I know the condition of the control unit points in that direction, but should I look more towards the Voltage Regulator Rectifier, I know it failed once before I bought the ATV because the old one was still attached to the frame.

I included a picture of the control unit to show it's condition.

Any advises are welcomed

Thanks for your help
4333
 

·
Super Moderator
Joined
·
3,694 Posts
OK - I answered one of your previous multiple posts and I now have a better understanding of what you are asking - What color wire goes to the pin that is missing? Short answer - no, there is no simple way to bypass the unit. It has little or nothing to do with spark, but the speedo does have something to do with spark - if the CPU in the speedo senses being in reverse (reverse light is on) it limits the speed when in reverse, bit if it gets a reverse and neutral signal at the came time (from ECU), it could shut off spark. Simply disconnecting the reverse lead (gray wire) from the gear position switch will eliminate the ECU from sensing the transmission being in reverse - if reverse continues to appear with the gray wire disconnected, either the gray wire is shorted to ground or the ECU is bad.

Also, I believe the plug with a missing pin is a 5 pin plug? Only 4 are used so I need to know what color wire goes to the missing pin.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #3
Ok I will check the color of the wire for the missing pin when I get to the TRX.

When you say disconnect the reverse lead (grey wire) from the gear position switch you mean to remove the grey wire from this part of the connector.

4334
 

·
Super Moderator
Joined
·
3,694 Posts
Whether you remove it at that connector or cut the wire and repair it later, yes, that is the wire that turns on the reverse light
 

·
Registered
Joined
·
8 Posts
Discussion Starter #6
Hi I just tried to cut the grey wire from the fear position switch and the red reverse light stays on.

for the control unit you are right the 5 pins connect to 4 wires. The missing pin on the ECU goes to the Red/yellow wire.
 

·
Super Moderator
Joined
·
3,694 Posts
Yellow wire with a red stripe or a red wire with a yellow stripe? If yel/red, it's the power wire from the fuse

Therefore the ECU has no power to that pin, but the ECU has other power inputs. If you study the wiring diagram, R2 red from the battery & R3 red from the solenoid go to a 2 position connector - R3 becomes R/W at the connector and both go to the fuse box - R/W goes to the motor fuse, becomes Y/R and goes to the ECU (I believe Y/R is the power wire for the electric shift motor which is controlled by the ECU.

R2 goes to the main fuse - from the fuse it becomes the R wire - R goes directly to the rec/reg and the key switch - at the key switch red is split and when the key is turned on, becomes black and Pink

The black wire (Bl) goes to the fuse box and feeds both the fan/horn fuse and accessory fuse
The pink wire goes to the light and ignition fuses

From the fan/horn fuse the wire becomes blue (Bu) - blue goes directly to the fan motor and nowhere else

From the accessory fuse the wire becomes white with a black stripe (W/Bl) - white/black goes to the accessory socket and nowhere else

From the light fuse, the pink wire becomes black with a brown stripe (Bl/Br) - Bl/Br goes to the dash indicator lights and the CPU - from the neutral & reverse LED's, the ground connections are made through the gear indicator switch - gray is reverse and goes from the led to the switch and to the ECU - the neutral LED ground is light green with a red stripe and goes from the LED to the gear change switch, the ignition module, ECU, starter solenoid and diode in the fuse box.

Yada, yada, yada - to make is as simple as possible, for the reverse light to be on with the gray wire disconnected, the ECU has to be defective or possibly does not have power to it on the red/yel pin

I recommend you use a straight pin or something similar to get 12v on the missing pin to see what happens. It may be all that is needed to fix it or it might reveal the actual component that caused the pin to burn or break off - inspect the plug carefully to see if the missing pin is actually lodged in the connector.



4342
 
1 - 7 of 7 Posts
Top