2013 Caprice 9C3 DOD disable in manual shift mode

Tech discussions on the L77 6.0L V8.
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Sanford
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Joined: Mon Dec 12, 2016 9:38 pm
Location: Texas Gulf Coast

2013 Caprice 9C3 DOD disable in manual shift mode

Post by Sanford »

I noticed when manually shifting the 2013 9C3 that I recently picked up, it does not go into 4 cylinder mode. Is this a feature of the 9C3 cars?. The car was fully warmed up and there are no check engine light on. At 60 miles an hour it stayed in 8 cylinder mode at light throttle on the same stretch of road that I drive everyday in drive. It usually will go into 4 cylinder mode on the level area and will go back to 8 cylinder when I get to the small overpasses that I cross. Wonder if anyone else with a 9C3 has noticed this.

David
lastcall190
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Re: 2013 Caprice 9C3 DOD disable in manual shift mode

Post by lastcall190 »

I don't have a 9C3 but I seem to recall G8 GTs *DO* and when they enter manual mode, DOD is similarly disabled. Perhaps this is similar/identical to that case.

-J
2012 Caprice
2008 CVPI

Both gone but not forgotten...
Navy Lifer
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Re: 2013 Caprice 9C3 DOD disable in manual shift mode

Post by Navy Lifer »

my recollection is that (regardless of anything to the contrary) this feature was only applicable in 6th gear--manual mode & lower gears retain AFM feature. I tried to determine if this was the case on my 2011 and never could figure it out, as far as whether it was disabled in 6M.

There was a bulletin that was issued for G8, that talked about this as far as a diagnostic process, don't recall that it carried over to PPV's.

Now running with no AFM (shut off at computer) and fuel economy does "suffer" as a result, but that's what a heavy foot gets me.
Sanford
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Location: Texas Gulf Coast

Re: 2013 Caprice 9C3 DOD disable in manual shift mode

Post by Sanford »

Took at look at what DOD does while shifting through the lowers gears and it appears to be disabled. I did notice that when you move the shifter over for the first time, it would go into 4 cylinder mode, but after a shift or two, it would keep the DOD disable. Would be interesting if the 2011 9C3's behave the same way.

If the DOD behaves the same on a 2011 9C3's, I may have to convert one of my 2011's to a G8 or 9C3 shifter, unless you have to get some new software. Hopefully one of the members that have converted a 2011 9C1 to a G8 shifter will chime in on how the conversion behaves.

David
smwalker
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Re: 2013 Caprice 9C3 DOD disable in manual shift mode

Post by smwalker »

From the service manual:

To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the cylinder deactivation system ON to deactivate engine cylinders 1, 7, 6, and 4, switching to a V4 mode. The engine will operate on 8 cylinders, or V8 mode, during engine starting, engine idling, and medium to heavy throttle applications.

Manifold absolute pressure (MAP) and the conditions listed below determine when cylinder deactivation is enabled.

Engine has been running for greater than 30 s
Engine speed is between 700 and 2800rpm
Engine oil pressure is between 187–455 kPa (27–66 psi)
Engine coolant temperature is between 40–129°C (100–264°F)
Engine oil temperature is between 16–128°C (61–263°F)
Throttle angle is 6% or less
Ignition voltage is greater than 11 V
Transmission is not in first, second, or reverse gear
Vehicle speed is greater than 25 kph (15.5 mph)
Brake booster pressure is greater than 42.0 kPa (6 psi)
Vehicle is not in fuel shut of mode
Vehicle is not in heater performance mode
Vehicle is not in tip in bump acceleration mode
Vehicle is not in oil aeration mode
Vehicle is not in low range (if equipped)
When cylinder deactivation is commanded, the ECM will determine what cylinder is firing and begin deactivation on the next closest deactivated cylinder in firing order sequence. For example, if cylinder number 1 is on its combustion event when cylinder deactivation is commanded ON, the next cylinder in the firing order sequence that can be deactivated is cylinder number 7. If cylinder number 5 is on its combustion event when cylinder deactivation is commanded ON, then the next cylinder in the firing order sequence that can be deactivated is cylinder number 4.

Cylinder deactivation is accomplished by not allowing the intake and exhaust valves to open on the selected cylinders by using special valve lifters. The deactivation lifters contain spring loaded locking pins that connect the internal pin housing of the lifter to the outer housing.

The pin housing contains the lifter plunger and pushrod seat which interfaces with the pushrod. The outer housing contacts the camshaft lobe through a roller. During V8 mode, when all cylinders are active, the locking pins are pushed outward by spring force, locking the pin housing and outer housing together causing the lifter to function as a normal lifter. When cylinder deactivation is commanded ON, the locking pins are pushed inward with engine oil pressure directed from the valve lifter oil manifold (VLOM) assembly solenoids. When the lifter pin housing is unlocked from the outer housing, the pin housing will remain stationary, while the outer housing will move with the profile of the camshaft lobe, which results in the valve remaining closed. One VLOM solenoid controls both the intake and exhaust valves for each deactivating cylinder. There are 2 distinct oil passages going to each cylinder deactivation lifter bore, one for the hydraulic lash-adjusting feature of the lifter, and one for controlling the locking pins used for cylinder deactivation.

Although both intake and exhaust valve lifters are controlled by the same solenoid in the VLOM, the intake and exhaust valves do not become deactivated at the same time. Cylinder deactivation is timed so that the cylinder is on an intake event. During an intake event, the intake cam lobe is pushing the valve lifter upwards to open the intake valve against the force of the valve spring. The force exerted by the valve spring is acting on the side of the lifter locking pins, preventing them from moving until the intake valve has closed. When the intake valve lifter reaches the base circle of the camshaft lobe, the valve spring force is reduced, allowing the locking pins to move, deactivating the intake valve. However, when cylinder deactivation is commanded ON, the exhaust valve for the deactivated cylinder is in the closed position, allowing the locking pins on the valve lifter to move immediately, and deactivate the exhaust valve.

By deactivating the exhaust valve first, this allows the capture of a burnt air/fuel charge, or exhaust gas charge, in the combustion chamber. The capture of exhaust gases in the combustion chamber will contribute to a reduction in oil consumption, noise and vibration levels, and exhaust emissions when operating in V4 mode cylinder deactivation mode.

During the transition from V8 to V4 mode, the fuel injectors will be turned OFF on the deactivated cylinders. To help prevent spark plug fouling, the ignition system secondary voltage or spark is still present across the spark plug electrodes on the deactivated cylinders. If all enabling conditions are met and maintained for cylinder deactivation operation, the ECM calibrations will limit cylinder deactivation to a cycle time of 10 minutes in V4 mode, then return to V8 mode for 1 minute.

Switching between V8 and V4 modes is accomplished in less than 250 milliseconds, making the transitions seamless and transparent to the vehicle operator. The 250 milliseconds includes the time for the ECM to sequence the transitions, the response time for the VLOM solenoids to energize, and the time for the valve lifters to deactivate, all within 2 revolutions of the engine crankshaft.

Valve Lifter Oil Manifold (VLOM) Assembly
The cylinder deactivation system uses an electro-hydraulic actuator device called the valve lifter oil manifold (VLOM) assembly. The VLOM is bolted to the top of the engine valley, below the intake manifold assembly. The VLOM consists of 4 electrically operated normally closed solenoids. Each solenoid controls the application of engine oil pressure to the intake and exhaust valve lifters on the cylinders selected to deactivate. Engine oil pressure is routed to the VLOM assembly from an internal oil passage on the rear of the cylinder block.

All 4 VLOM solenoids are connected in parallel to a fused ignition 1 voltage circuit, supplied by the powertrain relay. The ground or control circuit for each solenoid is connected to a low side driver internal to the engine control module (ECM).

When all enabling conditions are met for cylinder deactivation, the ECM will ground each solenoid control circuit in firing order sequence, allowing current to flow through the solenoid windings. With the coil windings energized, the solenoid valve opens, redirecting engine oil pressure through the VLOM into 8 separate vertical passages in the engine lifter valley. The 8 vertical passages, 2 per cylinder, are connected to the valve lifter bores of the cylinders to be deactivated. When vehicle-operating conditions require a return to V8 mode, the ECM will turn OFF the control circuit for the solenoids, allowing the solenoid valves to close. With the solenoid valves closed, engine oil pressure in the control ports is exhausted through the body of the solenoids into the engine block lifter valley. The housing of the VLOM incorporates several bleeds in the oil passages to purge any air trapped in the VLOM or engine block.

To help control contamination to the hydraulic circuits, a small replaceable oil screen is located in the VLOM oil inlet passage, below the oil pressure sensor. The oil pressure sensor is a 3-wire sensor which provides oil pressure information to the ECM.

During service, use extreme care in keeping the VLOM assembly free of any contamination or foreign material.

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 is active
Reduced engine power is active
Torque management is active
Catalytic converter over temperature protection is active
Piston protection is active, knock detected
Cylinder deactivation solenoid driver circuit faults
Steve Walker
Azusa, CA
'11 PPV 9C3 Huron White
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Mooseman
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Re: 2013 Caprice 9C3 DOD disable in manual shift mode

Post by Mooseman »

Actual fuel economy with DOD is debatable. I tried it with and without (by unplugging the vacuum booster sensor) and had no better fuel economy on the exact same highway trip. Noticed that it doesn't stay in V4 mode very much and would go into V8 mode at the slightest incline using cruise control. And that it must switch to V8 mode at least every 10 minutes doesn't help. I never saw it stay that long and would probably never happen unless you're driving through Saskatchewan :D
2011 Caprice PPV, former RCMP test vehicle, never put into service
Build Thread: http://www.newcaprice.com/forum/viewtopic.php?t=2419
muscleparts
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Re: 2013 Caprice 9C3 DOD disable in manual shift mode

Post by muscleparts »

Probably a Bad question, but im stuck at work and cant get much stuff to load to research but, What other functions and / trouble codes would leaving the vacuum booster sensor disconnected. probbably a too simple way to deactivate DOD.
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Mooseman
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Re: 2013 Caprice 9C3 DOD disable in manual shift mode

Post by Mooseman »

Just the CEL and code for that sensor. That's it. The Check Engine message comes up each time your start it, which is annoying but that really is all. DOD will not engage with that sensor unplugged.
2011 Caprice PPV, former RCMP test vehicle, never put into service
Build Thread: http://www.newcaprice.com/forum/viewtopic.php?t=2419
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