Logo
FULL SITE MENU

BF90D 41-2 H02S Heater Failure

JY Marine

JY Marine

Member
Hey everyone, just found out about this site recently and decided to sign up to see if i can get help on a issue that I'm having.

BF90D BBCJ-1005202 VTEC 4 Stroke

I have an engine code/alarm 41-2 o2 heater failure.

Ive rebuilt the motor with 190psi each cylinder and runs beautiful and very smooth, checked up on the wiring on the plug to the ecu, injectors, spark plugs, fuel pump, regulators and even tried 3 aftermarket sensors (Ive heard aftermarket sensors are a no go but I've bought them just to see if the code will go away so i can buy the genuine sensor which is pricey since I'm from Australia) but the code and alarm is still there after i start the motor with a continuous beeping alarm from control box. Which now I’m stuck since there is nothing left to check up on. just wondering now do i need to buy a genuine o2 sensor for the code to go away, or do i need to buy a new ecu which i highly doubt it fried because its only has 231 hours. Ive heard the ecu has a specific ohms reading to the o2 sensor which is why maybe the aftermarket sensors didn’t work, if someone can help me if I've missed something to check up on or if anyone knows what my next step should be would be much appreciated.

Thanks, Greetings from Australia

PS, ive been trying to figure out the problem for months and just given up on it but since summer is coming up down here might as well give it a crack again and spend on fixing the problem again.
 
You might try contacting forum member ian6766 by private message.

He has a shop in Australia and is a very knowledgeable outboard mechanic. He's probably extremely busy right now though.

I don't have any experience with this outboard or SI (service info) on it but am interested in how you're accessing that code and interpretation.

The reason I ask is because, in my o documentation for the older, larger displacement Hondas... ie: 225, 200 and 175 horsepower,...there's no dash "extension".for the 41code as you've listed (-2)

The code description/interpretation looks similar to what you've listed about the O2 sensor connectivity but it also lists "spark plug misfire".

Wondering if your info includes that suggestion and, if so, have you looked into that "angle" of this difficult to diagnose problem.

Just curious really.

Good luck.
 
I think you may have a water in fuel alarm. Have you tried clearing the fault. the O2 sensor fault you are seeing may be an old fault that hasn't been cleared
 
iang6766 said:
I think you may have a water in fuel alarm. Have you tried clearing the fault. the O2 sensor fault you are seeing may be an old fault that hasn't been cleared
Click to expand...
I’ve cleared it so many times, water in fuel alarm? Does that have a sensor? If so do you know where it is? Ive heard alot of different faulty sensors can cause the o2 sensor to throw a code but whats confusing me is that usually will throw just a normal o2 failure code but mine is throwing ho2s heater failure.
 
There's a water separator with a sensor right under the throttle body. The O2 sensors are half gge Aus price if sourced from Yumbo parts in Japan. The reason I think it's a water alarm is because you say it starts beeping immediately on start up. O2 sensor heater failure usually only alarms after extended idle time, it also usually caused a rich, rough idle condition. I never use those cheap after market sensors, not even on my own motor. Where are you located?
 
iang6766 said:
There's a water separator with a sensor right under the throttle body. The O2 sensors are half gge Aus price if sourced from Yumbo parts in Japan. The reason I think it's a water alarm is because you say it starts beeping immediately on start up. O2 sensor heater failure usually only alarms after extended idle time, it also usually caused a rich, rough idle condition. I never use those cheap after market sensors, not even on my own motor. Where are you located?
Click to expand...
Sorry for the confusion, my alarm beeps like around 4 seconds after the motor has started.
Located Victoria, Melbourne
 
JY Marine said:
I’ve cleared it so many times, water in fuel alarm? Does that have a sensor? If so do you know where it is? Ive heard alot of different faulty sensors can cause the o2 sensor to throw a code but whats confusing me is that usually will throw just a normal o2 failure code but mine is throwing ho2s heater failure.
Click to expand...
I have this same problem currently on a Honda BF75D (same powerhead as BF90D). Did an OEM replacement sensor fix your problem of the code 41-2? I am also using heal tech diagnostic.
 
DoubleSeas said:
I have this same problem currently on a Honda BF75D (same powerhead as BF90D). Did an OEM replacement sensor fix your problem of the code 41-2? I am also using heal tech diagnostic.
Click to expand...
Hey sorry to hear that you have the same problem, i bought a genuine o2 sensor but still didn’t fix the fault/alarm. I finally found the issue and fixed it, it was my ECU, found out that the ecu has a ground circuit driver specifically for heater circuit ground in the ecu that was fried. The way I concluded that the ecu was the issue was i done a specific test. The 4 pin o2 connecter you have 2 wires that are the same colour usually white, find the one that is the heater GROUND wire (and the other one is the heater signal wire) you find the ground wire by multimeter one lead goes to the pin and one to engine ground, both pins will you give 12v but when you start the engine one the wires should drop to 0v in under 3-5 seconds and gradually work its way up back to 12v hence why my alarm only started beeping 3-5 seconds after running the motor. So you're going to have to try it 2 times the test for each of the heater wires. When you found the ground heater wire and it stays on 12v even after 5 seconds of start up it means the heater ground circuit is open meaning the driver inside the ecu is burnt. If it only drops down to 4-5 volts it means wiring resistance, corroded connector, or partial short, the correct thing it should do is drop straight away to 0v after 3 -5 seconds of staring your motor. So thats the way i found out 100% if it was the ecu fault instead of me risking to go buy a ecu and turn out not to be that. Also if you think its just the o2 heater circuit inside your sensor you can get the 2 wires and check the ohms it should read I believe 10-40 ohms. 0 ohms and continuous ohms means sensor heater is bad.


Note: when testing the 2 wires for the ecu test just dont forget they will both give you 12v when starting the motor, only one the the heater wires will give you 12v then 3-5 seconds later drops to 0v, the other wire is just the heater signal with constant 12v then on starting the motor will go up to roughly 12.50v-13v (due to power charge from stator).

The issue with this motor before i found out about this o2 issue was water was mixing with oil in cylinder 1 (pinholes in exhaust jacket and near spark plug due to previous owner not flushing the motor and taking care of it)
Which then led to the engine overheat and that is why i think thats when the o2 shorted out the ecu, because as we know when it comes to o2 sensors for Honda's, they are very SENSITIVE, one drop of oil or water touches the reading part of the sensor inside and it will send crazy information to the ecu and the ecu will most likely freak out and open and close the circuit continuously (for the safety of the engine) which then destroys the heater inside the o2 while also burning the driver that controls the circuit inside the ecu

Whoever is reading this i hope you dont go the same pathway i did with spending continuous amount of money buying aftermarket sensors and genuine sensors when you can just test and find the problem using a multimeter. I hope this answer/solution helps anyone that has to go through this.

Wish youse all the best!
 
Great write up! Thank you for taking the time.

It's BOUND to help someone save a bundle in time and $$$$ chasing this code/problem.
 
That is a very detailed write up. I am waiting on my new (used) ECU to show up. I noticed some corrosion on the pins of the ECU, I very gently took a light wire brush and contact cleaner to them and had two pins break off. The corrosion at the base of the pin had eaten it away and it took almost no force to snap it off. Hopefully someone else can use all of this info in the future!
 
Back
Top