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Discussion Starter · #1 ·
I had the VTM-4 and VSA light on so I changed the VTM-4 fluid and the sensor that mount onto the rear differential. Next thing I knew the ABS, VTM-4, CEL and the wording VSA and the triangle w/exclamation point are lit after I drove about few miles down the road. Just the other day I got the ABS and VTM-4 light to turn off. The VSA and triangle w/exclamation point are still lit. I try to jump the harness pin 4 and 9 that I found on youtube it did not help. Oh by the way the CEL I scanned it and was throwing a P0154, Oxygen Circuit No Activity Detected (Bank 2 Sensor 1) so I cleared it from the scanner. I'm keeping an eye on it to see if it comes back on.

I called up (2) of my friends that own a full shop. The first friend I talk to said you need to program the VSA sensor neutral position and he does not have the computer/scanner to do it. I called up my second friend he said he has the computer/scanner to reprogram the VSA. I'm taking my MDX this Friday to have the VSA program. Is it safe to drive it to the shop that's about 45miles away highway speed without any damage to the VSA/VTM-4?
 

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Discussion Starter · #2 ·
FIXED

I drove it to the shop clear and reset the ECU last Friday. I drove it around and the light came back on. My friend had to leave the shop. I drove it down to my other friend shop and he order me a O2 sensor (upstream) and install it and reset/clear the ECU codes. Drove it about 15-20 miles and everything back to normal and all the lights are off on the cluster. Trying to figure out how an O2 sensor trigger the VSA, /!\, VTM-4, ABS, and the Airbag light to turn on?

The only thing left to do is change out all the fluid minus the oil.
 

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I can't imagine an O2 sensor causing all those symptoms, unless maybe it was shorted out to the point that it was causing other problems with the ECU (but even then, I think the ABS and Airbag systems are entirely separate). Looking for a common thread would have me suspecting a bad system ground or other "major" wiring issue. But with any luck, the lights will stay off and you can just put it all down as one of life's little mysteries. ;-)
 

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In the 2G MDX anything related to emissions will cause the SH-AWD to be disabled so it makes sense that it happens too with VTM4.
 

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Discussion Starter · #5 ·
I kind of figure that it disable the units. Could not understand why Acura/Honda design something like this due to safety issue?

I love to find a circuit wiring diragram to understand it better.
 

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I think it's because of emissions..
When a o2 sensor fails the engine has to run in an Open Loop which will cause worse MPGs and more emissions.. If it disables the AWD the engine runs with less load which should somewhat even things out.

That is just my theory though..
 

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Discussion Starter · #7 ·
When the motor is only purpose to convert a form of energy to mechanical energy.
Torque Converter transmit torque generated by an engine/motor.
Transmission is something that transmitted for example power from an engine to the wheels.
Transfer case it to transfer power from the transmission to the front and rear axles.

The ECU uses feedback form the sensor to adjust the fuel/air mixture. When the O2 sensor goes bad the ECU have a hard time adjusting the correct air/fuel mixture.

EDIT:
I just found my answer :)

2. Slip Control Logic
The second engagement mode uses wheel slippage control logic. If the difference in rotational speed between front and rear wheels rises because of a slippery surface or poor traction at the front of the vehicle, that condition is detected by wheel-speed sensors which are monitored by VTM-4's ECU. In response, the ECU commands an increasing amount of torque for the rear wheels. Torque is proportional to both slip rate and the rate at which the slip rate is increasing.
http://www.dansher.com/misc/VTM-4_fyi.pdf

My guessing is that the O2 sensor is also monitor by the ECU and some how it maybe using the same signal or ground and that tied in with the wheel-speed sensor. If one sensor goes bad it run into an open loop instead of a close loop.

I'm a Mechatronics (Electrical-Mechanical) engineer by trade. I was thinking as an Engineer. It's my nature to find out why it did it with a 100% complete correct answer.
 

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The o2 sensor is not tied in any way to the speed sensor. o2 Sensors feed directly to the ECU. Wheel speed sensors are connected to the ABS System.
 

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Speed sensors mess with the AWD because there is no way to control slippage if a speed sensor is broken or disconnected. Thus the system cannot read road conditions and slip to send power to the rear wheels.
 

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It's just part of the "Limp Home" or "Power Derate" mode used by many companies. The PCM has an internal list of codes that may require reducing engine power or load to prevent possible damage to the drivetrain. When one of those codes is set, certain alternate programming comes into play.

One thing for sure - You gotta be really dense to miss all those lights when they come on. :)
 

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Discussion Starter · #11 ·
It's just part of the "Limp Home" or "Power Derate" mode used by many companies. The PCM has an internal list of codes that may require reducing engine power or load to prevent possible damage to the drivetrain. When one of those codes is set, certain alternate programming comes into play.

One thing for sure - You gotta be really dense to miss all those lights when they come on. :)
After looking at a random schematic drawing that my nephew provided (Honda Mechanic). I understand it allot better and now I can see that possibility when it went into Limp mode it shuts down the control modules.
 

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It's just part of the "Limp Home" or "Power Derate" mode used by many companies. The PCM has an internal list of codes that may require reducing engine power or load to prevent possible damage to the drivetrain. When one of those codes is set, certain alternate programming comes into play.

One thing for sure - You gotta be really dense to miss all those lights when they come on. :)

Have you guys ever encountered putting an aftermarket cv axle on the passenger side, and now it keeps throwing a speed sensor code? Replaced the sensor and wire harness, and it resets when I turn off my car, like it's trying to reset, but then throws the code after a couple of miles. Not sure what to do. Already replaced the sensor.
 

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I have to say no body has a clue of automotive communications of operations (sensors signal's,sensor signal return,ecu operations to correct values back to 14:7:1 ratio .air/fuel ratio of 14:7:1 is making water out the tailpipe ,Automotive systems have become VERY complex at all levels . I am quite knowledgeable in automobile operations of systems and there are many very knowledgeable Tech's that leave us with lots of problems to fix that accure from many ways. I am not knocking any opinions I just do not have time for solutions with guesses . I am looking for possible solution to a VSA malfunction resulting 40-45mph when VSA light/on and back to normal light/off . does any one have knowledgeable time with this system ? 05 mdx 3.5 i'm looking towards software update to rewrite ecu values
Thank's
 

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sorry, I did not mean to down anyone I am looking for confident answers without long conversations ,this system is new to me and I was pushed for time .I also have a 2000 RL with no fire issue in my shop ,replaced ign module,crnk sens,main relay,no codes ,original red key no security problems this is one of these that has water leaking inside fearing the worst .
 
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