Ecotec3 5.3L AFM Cylinder Deactivation Issue

[uptou2bu]

2014 Silverado LTZ 4x4 Ecotec3 5.3L While driving on the with the cruse control on or manual acceleration on interstate cylinder deactivate turns off at 59 mph. If I drop it back down to 58 it starts working again. Also when idling it stays in 8 cylinder mode. Does anyone have a clue on this.

[Poltergeist]

It always idles in V8 mode, any speed below about 20 you are in V8 mode. One thing that also controls AFM is throttle position. Even though you may not be acceralting you may be pushing the throttle too far. Takes just a bit of release of throttle will probably drop you back to V4. With cruise control I've noticed it's hit and miss.

[uptou2bu]

The reason I am asking about truck idling in 4 cylinder mode is because of the 01/2014 GM recall letter stating that the vehicle is supposed to idle in 4 cylinder mode and some of them weren't which in return was causing the exhaust to overheat and setting the truck on fire. (8 Trucks were burned according to recall letter)

The other part which describes the AFM not working at 59 mph I know for a fact is defective and should not operate this way. My coworker owns the same vehicle and it functions properly, the only time the AFM disengages is when the brake is applied while on cruse control and small variations in the speed do not affect it. This is also the same for my truck as long as I stay below 59 mph.

My question what is wrong with this vehicle, not if there is something wrong with.

[glcbn]

Not sure where that info came from, but never heard/read, or ever witnessed my truck idle in V4. I think there is maybe some typo somewhere, or possible misinterpretation.

 

Are you saying your truck will not go into AFM above 59 mph? If that's the case, sounds like a trip to the dealer diagnostic machine.

[Poltergeist]

There was a site that reported that the truck would not idle in v4 and a bunch of other sites picked up the story and re-ran it. The original story was wrong.

[Z45]

Also note there is a time limit for AFM to stay engaged.

 

Cylinder Deactivation Inhibit Reasons

Listed below are the powertrain conditions that will inhibit V4 mode, while operating under light load driving conditions:

 

Engine manifold vacuum low

 

Brake booster vacuum pressure low

 

Accelerator pedal position rate of increase too high, electronic throttle control

 

Accelerator pedal position too high, electronic throttle control

 

Ignition voltage out of range

 

Engine oil pressure out of range

 

Engine oil temperature out of range

 

Engine RPM out of range

 

Transmission gear incorrect

 

Transmission range incorrect

 

Transmission gear shift in progress

 

All cylinders activated via scan tool output control

 

Minimum time in V8 mode not met

 

Maximum V4 mode time exceeded

 

Engine oil aeration present

 

Decel fuel cutoff active

 

Fuel shut-off timer active

 

Minimum heater temp low, HVAC system

 

Reduced engine power active, electronic throttle control

 

Brake torque management active

 

Axle torque limiting active

 

Engine metal over temperature protection active

 

Catalytic converter over temperature protection active

 

Piston protection active, knock detected

 

Hot coolant mode active

 

Engine over speed protection active

[chuckl1218]

If you are referring to Recall 14008 from 1/2014, it does not mention idling in V4 (my truck has never idled in V4 whether under remote start or sitting at a traffic light ). What it does say is "Some of the exhaust components may overheat, when your vehicle is idling in cold temperatures. If this were to occur, the yellow Check Engine light will illuminate and the "Engine Power is Reduced" message will appear in the Driver Information Center (DIC). If there is enough heat, it could melt plastic parts in the area, resulting in a possible fire." The remedy was for the dealer to reprogram the engine control module to modify the Power Management Mode software in order to prevent this condition. As I recall there were changes to idle RPM and lean/rich fuel setting or make it run cooler under remote start conditions. After the recall, there were a lot of complaints that trucks would not heat up enough to warm up interior heated air. I've never seen idle in V4 mode under any of these conditions.

 

I have seen V4 at 70mph on flat terrain, at 65mph with slight gas pedal pressure, when decelerating on an off ramp, but mainly at 35 - 55 steady driving even up slight grades. But once there is any load, V8 kicks in. Example...I drove from Austin to Houston and saw V4 a lot, mostly on flat terrain. However, when I returned, it was windy and raining. It stayed in V8 all of the way home. Not saying you're truck isn't having issues, but any of the above conditions or difference in driving style could cause differing results.

 

Hard to say what is wrong other than one of the control modules...I agree with glc, trip to the dealer

[uptou2bu]

I have did more research and the idle issue I read about is refering 14008/14008B and niether says anything about idling in V4 mode. So that question is solved.

 

As for the second part of my question, yes I am saying that when I drive down the interstate on a perfectly flat roadway and set the cruse control at 59mph or above it will never go into V4 mode until I hit the down side of a overpass and then right back to V8 mode. They are trying to tell me this is normal. I drove over 600 miles on the interstate and it did this the entire time. (16.5 mpg )

[glcbn]

I have did more research and the idle issue I read about is refering 14008/14008B and niether says anything about idling in V4 mode. So that question is solved.

 

As for the second part of my question, yes I am saying that when I drive down the interstate on a perfectly flat roadway and set the cruse control at 59mph or above it will never go into V4 mode until I hit the down side of a overpass and then right back to V8 mode. They are trying to tell me this is normal. I drove over 600 miles on the interstate and it did this the entire time. (16.5 mpg )

 

Normal my ass! You definitely have an issue. Just did some checking today. Cruise set at 75 and it will go into V4. Does your cruise hold a constant speed regardless of grade? Talking normal/average highway gradient. Nothing severe. Just wondering because mine never deviates from what I set.

[uptou2bu]

Greg, yes it does hold the set speed constant with no variation at all. My co-worker has had the same results as you with no issues in V4 mode on the highway with cruise set. It has totally pissed me off that the dealerships (2 for me so far) would be telling customers that this is normal. For these systems to preform as mine does completely defeats the purpose they were designed for in my opinion.

[glcbn]

Greg, yes it does hold the set speed constant with no variation at all. My co-worker has had the same results as you with no issues in V4 mode on the highway with cruise set. It has totally pissed me off that the dealerships (2 for me so far) would be telling customers that this is normal. For these systems to preform as mine does completely defeats the purpose they were designed for in my opinion.

 

Man,I feel for you when comes to dealing with dealers. Don't know what to tell you other than maybe get GM Customer Care involved if you still aren't having any luck getting them (dealer) to diagnose your truck.

[uptou2bu]

Thanks

[RandyMarsh509]

2014 Silverado LTZ 4x4 Ecotec3 5.3L While driving on the with the cruse control on or manual acceleration on interstate cylinder deactivate turns off at 59 mph. If I drop it back down to 58 it starts working again. Also when idling it stays in 8 cylinder mode. Does anyone have a clue on this.

Did you ever get this fixed/found out what the real issue was?

I'm noticing mine doesn't go into V4 nearly as much as I thought it would.

 

I realize it's probably a dumb question but has anyone found a way to manually turn the AFM on/off?

[davidio840]

Did you ever get this fixed/found out what the real issue was?

I'm noticing mine doesn't go into V4 nearly as much as I thought it would.

 

I realize it's probably a dumb question but has anyone found a way to manually turn the AFM on/off?

 

Check out Range Technology AFM delete. They also have one that will use the AFM more if you are into that.

[uptou2bu]

Sorry been away,no I gave them the truck back and never heard another word from them. The guy I work with is getting 21mpg to and from work. also he is running 20" tires and has absolutely no issues.