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AFM not working at higher speeds?

GMcD

By GMcD
in Troubleshooting & Recalls

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GMcD Enthusiast

GMcD

Posted
Posted

I have had my 2014 Silverado about 5 weeks and love it other than a paint issue (currently getting repaired). On the way to take it to the body shop (4.5 hours away), I noticed that my truck rarely dropped into v4 mode. It didn’t matter if it was flat or down hill, it wouldn’t engage. This was with cruise control on. After watching it for the next hour or two, it seems to work with the cruise control off. I also noticed that if i get to my target speed (say 78mph), that if i enabled cruise with v4 mode on, v4 mode was more likely to activate with cruise control on. Is this a known issue and if so, whats the fix? 

KARNUT Senior Enthusiast

KARNUT

Posted
Posted

I turned mine off. In your case the higher the speed the more wind drag less V4 mode.


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aseibel Senior Enthusiast

aseibel

Posted
Posted

If you set the cruise at 60 mph on flat terrain, it should stay in v4 most of the time.

 

Truck is fighting way too much wind at 78 mph. If you are driving 78 mph, I'm guessing fuel efficiency is not your top priority.

Z45 Senior Enthusiast

Z45

Posted
Posted

I agree.    Not a problem.  Mine works on cruise control at 60 mph.

 

 

Cylinder deactivation may be inhibited for many reasons including the following:

 

• Engine coolant temperature out of range for cylinder activation
• Engine vacuum out of range
• Brake booster vacuum out of range
• Transmission gear incorrect or shift in progress
• Accelerator pedal out of range or rate of pedal application to fast
• Engine oil pressure and temperature out of range
• Engine speed out of range
• Vehicle speed out of range
• Minimum time in V8 mode not met
• Maximum V4 mode time exceeded
• Decel fuel cutoff active
• Reduced engine power active
• Torque management active
• Catalytic converter over temperature protection active
• Piston protection active, knock detected
• Cylinder deactivation solenoid driver circuit faults
Cheverado Enthusiast

Cheverado

Posted
Posted
2 hours ago, GMcD said:

I have had my 2014 Silverado about 5 weeks and love it other than a paint issue (currently getting repaired). On the way to take it to the body shop (4.5 hours away), I noticed that my truck rarely dropped into v4 mode. It didn’t matter if it was flat or down hill, it wouldn’t engage. This was with cruise control on. After watching it for the next hour or two, it seems to work with the cruise control off. I also noticed that if i get to my target speed (say 78mph), that if i enabled cruise with v4 mode on, v4 mode was more likely to activate with cruise control on. Is this a known issue and if so, whats the fix? 

V6 or V8?

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
13 minutes ago, elcamino said:

I agree.    Not a problem.  Mine works on cruise control at 60 mph.

 

 

Cylinder deactivation may be inhibited for many reasons including the following:

 

• Engine coolant temperature out of range for cylinder activation
• Engine vacuum out of range
• Brake booster vacuum out of range
• Transmission gear incorrect or shift in progress
• Accelerator pedal out of range or rate of pedal application to fast
• Engine oil pressure and temperature out of range
• Engine speed out of range
• Vehicle speed out of range
• Minimum time in V8 mode not met
• Maximum V4 mode time exceeded
• Decel fuel cutoff active
• Reduced engine power active
• Torque management active
• Catalytic converter over temperature protection active
• Piston protection active, knock detected
• Cylinder deactivation solenoid driver circuit faults

Good info. Where did you come by it? 

GMcD Enthusiast

GMcD

Posted
  • Author
Posted

My truck is a v8. Wind resistance does make sense as well. Ill try 70mph next time and see what happens. Thanks

  • 2 months later...
Ohio_Farmer New Member

Ohio_Farmer

Posted
Posted

New member - this is a great a great forum.

 

I just took delivery of a 2018 Silverado with the 6.0. I was disappointed (at first) that it did not have AFM. I had rented a pickup with a 5.3 and really enjoyed the fuel economy and was looking forward to it on our 2018. But after joining this forum and reading some of the horror stories, I am glad it is a straight up 6.0.

 

I traded in my 2005 2500 with a 6.0 and the engine still ran great but was developing low oil pressure only on start up. With 300K miles, I guess that is a fairly well known issue. A crate motor would have been around $6000 and we just decided it was time to replace the old girl.

 

Question: does anyone know why this truck has a 2.5" receiver and then they give you a 2" sleeve?

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