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Discussion Starter · #1 ·
Team, I tried a certain brand of disabler today on my 2021 Pilot,.

I noticed a positive change in driving my car on the freeway. Before on long, flat roads Fuel Trim % Bank 1 would go to zero for long periods of time. I understand that tells me VCM is on. With the disabler product, I no longer see zero on the fuel trim on the freeway.

However, I can still make the car go to zero % on Fuel Trim % Bank 1, by getting the car in 9th gear on a flat road and taking my foot off the gas and then coast. I will coast for a while with zero percent and can feel as the car downshifts, fuel trim with shoot up, then go back to zero as I coast.

Do these devices disable VCM all the time, or are there still conditions where it will enable.

Thank you!
 

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Curious, what does Bank 2 show when you coast under the same circumstances?

From my (admittedly limited) understanding of engines, I believe the ECU cuts fuel while coasting until the engine can no longer turn itself over. This is typical of modern engines, not unique to cylinder deactivation tech.

This is an older article, but I think the explanation holds true. Open to being corrected if I'm mistaken.
 

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Discussion Starter · #3 ·
Curious, what does Bank 2 show when you coast under the same circumstances?

From my (admittedly limited) understanding of engines, I believe the ECU cuts fuel while coasting until the engine can no longer turn itself over. This is typical of modern engines, not unique to cylinder deactivation tech.

This is an older article, but I think the explanation holds true. Open to being corrected if I'm mistaken.
Thanks Viper, I will go test that...
 

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When you take your foot off the gas and coast, both fuel trims will go to zero. This is normal and it is just the PCM estimating the fuel required based on the Throttle Position and engine rpm. The VCM does shut off fuel to bank1 under coasting and low load conditions and the Bank 1 fuel trim will zero out when it is activated while bank2 will fluctuate. Fuel trims should be checked at idle, 1500rpm and 2500 rpm if you are trying to diagnose fuel issues and they should be in the -5% to +5% range at steady rpm if everything is normal. If they are running rich , greater than -10% chances are that your injectors are on the way out.
The SVCM that I have installed does not allow the VCM to activate as it keeps the coolant temp reading below 165°F and the only time it will bypass is if the actual coolant temp reaches 205°F and under those conditions the VCM would still activate.
 

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Discussion Starter · #5 ·
When you take your foot off the gas and coast, both fuel trims will go to zero. This is normal and it is just the PCM estimating the fuel required based on the Throttle Position and engine rpm. The VCM does shut off fuel to bank1 under coasting and low load conditions and the Bank 1 fuel trim will zero out when it is activated while bank2 will fluctuate. Fuel trims should be checked at idle, 1500rpm and 2500 rpm if you are trying to diagnose fuel issues and they should be in the -5% to +5% range at steady rpm if everything is normal. If they are running rich , greater than -10% chances are that your injectors are on the way out.
The SVCM that I have installed does not allow the VCM to activate as it keeps the coolant temp reading below 165°F and the only time it will bypass is if the actual coolant temp reaches 205°F and under those conditions the VCM would still activate.
Thank you. I will go monitor both fuel trims.(y)
 

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When you take your foot off the gas and coast, both fuel trims will go to zero. This is normal and it is just the PCM estimating the fuel required based on the Throttle Position and engine rpm. The VCM does shut off fuel to bank1 under coasting and low load conditions and the Bank 1 fuel trim will zero out when it is activated while bank2 will fluctuate. Fuel trims should be checked at idle, 1500rpm and 2500 rpm if you are trying to diagnose fuel issues and they should be in the -5% to +5% range at steady rpm if everything is normal. If they are running rich , greater than -10% chances are that your injectors are on the way out.
The SVCM that I have installed does not allow the VCM to activate as it keeps the coolant temp reading below 165°F and the only time it will bypass is if the actual coolant temp reaches 205°F and under those conditions the VCM would still activate.
This is the way I understand most fuel injected vehicles treat a full coasting, 0% throttle scenario while at speed.
 

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Discussion Starter · #7 ·
When you take your foot off the gas and coast, both fuel trims will go to zero. This is normal and it is just the PCM estimating the fuel required based on the Throttle Position and engine rpm. The VCM does shut off fuel to bank1 under coasting and low load conditions and the Bank 1 fuel trim will zero out when it is activated while bank2 will fluctuate. Fuel trims should be checked at idle, 1500rpm and 2500 rpm if you are trying to diagnose fuel issues and they should be in the -5% to +5% range at steady rpm if everything is normal. If they are running rich , greater than -10% chances are that your injectors are on the way out.
The SVCM that I have installed does not allow the VCM to activate as it keeps the coolant temp reading below 165°F and the only time it will bypass is if the actual coolant temp reaches 205°F and under those conditions the VCM would still activate.
You were right..both trims go to zero.. (y)
 

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