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Wondering why my VTM-4 light comes on and why 4WD won’t engage. I have a 2005 Honda Pilot EX-L 4WD. I have no TPMS sensors on the tires so my tpms light and “flat tire” light is constantly on, I also have a check engine light for a o2 sensor (that i replaced 8 months ago so not sure if it’s bad or if it’s the fact that i might have a bad catalytic converter) I’m basically wondering if any of those issues with my car might be throwing my VTM-4 light on. Recently went camping got into a situation where i needed to use 4WD and it wouldn’t engage despite doing everything correctly, so I can’t tell if those other issues are disengaging my 4WD or if my 4WD is screwed. Would appreciate feedback thanks.
 

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Welcome @brunettebunnie ... post whatever codes you have for internet discussion. List any maintenance items that have been completed like trans fluid, rear diff service etc. Local auto parts stores like Advance/Autozone can do free scans.
 

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Code on car is P2240, nothing maintenance done other than oil change and new tires haven’t had the car long just for a year. Don’t really need to get anything scanned, have a scanner at home for codes.
 

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Yes, definitely change out your VTM-4 fluid (no substitutes), especially if you have no record of it ever being done.
 

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Yes, definitely change out your VTM-4 fluid (no substitutes), especially if you have no record of it ever being done.
Check out this video perhaps this might match the problems you are having otherwise it has a good overview of servicing the rear diff fluid.


Thank you! I will be trying that tomorrow to see if it fixes my light problem.
 

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In most cases, if you have an impaired emissions system triggering the check engine light (CEL), that will disable the VTM-4 system. The VTM-4 light illuminates and the switch is no longer active on the dash.



Honda integrated the rear differential with the motor, so that anytime the car is underpowered (anything to do with emissions, misfires, etc.) the computer effectively disables the VTM system. The computer thinks your car is underpowered, so by disabling the VTM this directs all the power to the front wheels, which in effect turns your AWD into a 2WD Pilot.

My guess is there's probably nothing wrong with your rear end/VTM-4 system, and if you fix the O2 sensor problem your VTM system will likely go back online. If you have a scanner that reads the VTM system and Honda codes you can determine if you have a separate issue with the rear end, but you'll definitely need to deal with the CEL.
 

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Discussion Starter #8
In most cases, if you have an impaired emissions system triggering the check engine light (CEL), that will disable the VTM-4 system. The VTM-4 light illuminates and the switch is no longer active on the dash.



Honda integrated the rear differential with the motor, so that anytime the car is underpowered (anything to do with emissions, misfires, etc.) the computer effectively disables the VTM system. The computer thinks your car is underpowered, so by disabling the VTM this directs all the power to the front wheels, which in effect turns your AWD into a 2WD Pilot.

My guess is there's probably nothing wrong with your rear end/VTM-4 system, and if you fix the O2 sensor problem your VTM system will likely go back online. If you have a scanner that reads the VTM system and Honda codes you can determine if you have a separate issue with the rear end, but you'll definitely need to deal with the CEL.

Thank you. I am going to look at my options and see what to start eliminating first. This weekend I might get my catalytic converter looked at and if it’s bad i’m going to potentially hollow out or get a universal cat (the state i live in doesn’t do emissions) because that could be throwing me an o2 sensor code since my o2 sensor is only 8 months old it shouldn’t be bad and it’s not loose. If it turns out my cat is fine I’m going to go ahead and replace the o2 sensor and hope that fixes the check engine light, which will hopefully fix my vtm-4 light. if it doesn’t fix my vtm-4 i will then go ahead and see if i can get a scan on my vtm-4 light or change the fluid and buy a new oil sensor for vtm-4 and see if that works.
 

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Note that a generic scanner will not read VTM-4 codes since they are Honda specific. There is a way to flash the main (but not sub codes) onto the dash by jumpering the OBDII port. Let us know if you need those instructions and I’m sure one of us can dig it up.
 

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Note that a generic scanner will not read VTM-4 codes since they are Honda specific. There is a way to flash the main (but not sub codes) onto the dash by jumpering the OBDII port. Let us know if you need those instructions and I’m sure one of us can dig it up.
Instructions would be helpful if any of you come across it! thank you
 

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Thank you. I am going to look at my options and see what to start eliminating first. This weekend I might get my catalytic converter looked at and if it’s bad i’m going to potentially hollow out or get a universal cat (the state i live in doesn’t do emissions) because that could be throwing me an o2 sensor code since my o2 sensor is only 8 months old it shouldn’t be bad and it’s not loose. If it turns out my cat is fine I’m going to go ahead and replace the o2 sensor and hope that fixes the check engine light, which will hopefully fix my vtm-4 light. if it doesn’t fix my vtm-4 i will then go ahead and see if i can get a scan on my vtm-4 light or change the fluid and buy a new oil sensor for vtm-4 and see if that works.
138568

😁👍
 
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Instructions would be helpful if any of you come across it! thank you

Materials:
-Paper clip or jumper wire.
-Honda service manual (for more specific info about code)

Basically, with car off and keys out, stick wire/paper clip into pins 4 and 9. Be careful to get those pins correct to avoid blowing a fuse, as you may be looking at them from upside down.

138571


138572


Then, found this, which should also help.

Look on page 15-10 of the service manual for the codes and their meaning. Page 15-7, step 5 shows how to count them. You can get to the service manual at:

138569


138570
 

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Note that other dash lights will blink as well if there are codes for those systems. If a system has multiple codes there will be a pause between each set of long and short flashes.
 
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Regarding the VTM specific trouble codes - if an engine/emissions problem triggers the CEL and disables VTM, the computer most often stores DTC 42-1 or 43-1.

I don't think that's written anywhere and it's just my observation. However, if you search the forum, that seems to be the most common code many of us recover when there's a random misfire or EGR problem. And when you fix the engine problem, the VTM resets, suggesting there wasn't a real problem with the pressure sensor or VTM fluid.

I haven't spoken with a Honda tech to confirm this thought, but the differential pressure sensor is probably the easiest path for the PCM to disable the VTM system.
 
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