2011 suburban 5.3, P3400 Diagnosis

Cylinder deactivation bank 1 trouble code:

Oil level and quality are fine
all deactivation solenoids will click when commanded by the scan tool
Pedal Position Sensor checks ok
TPS checks ok
Coolant Temp Sensor checks ok

ECM C2 14 Orange wire does not pull down to 0v when solenoid 6 is activated but will click (cylinder 6 is bank 2, not bank 1?) and I have conflicting information regarding what solenoid number activated which cylinder (I don't have access to Mitchel/Shopkey/Alldata, etc).

confusing me is the following

Cylinder Deactivation Disable History:
1 invalid
2 eng spd out of range
3 accel pdl pos inc Hi
4 eng spd out of range
5 invalid
6 eng oil pressure out of range
7 accel pdl pos inc Hi
8 eng oil pressure out of range

clear the code and test drive...

MAP sensor fault
MAP sensor out of range
invalid

Disable history keeps pointing in different directions, so I have no idea what direction to go in.

O2 B1-S2 appears dead, flat line unless I snap the throttle. Fuel trims are fine
A shop replaced both purge valves (canister & engine) & MAP sensor

Any idea how I can 100% verify a bad VLOM or rule it out and look for a sensor issue?

P3400 is a tough one to diagnose. It's a performance code, not a circuit code, unfortunately. Been there and all. From service info:

The Cylinder Deactivation System Performance diagnostic is a test of the internal mechanical condition of the engine, during operation in V4 mode. The engine control module (ECM) determines the internal mechanical condition of the engine through the actual measured values of the mass airflow (MAF) sensor, the intake manifold absolute pressure (MAP) sensor, and the throttle position sensor. The actual measured values of the 3 sensors are then compared to the calculated values for V4 mode, stored in the ECM. If the measured values are incorrect for V4 mode, the ECM will set DTC P3400, and will return to V8 mode operation.

What I got out of that is: The ECM has an idea of how the engine should be breathing in V4 mode. For whatever reason, your Suburban isn't conforming to that ideal. The ECM doesn't know why, only that the two didn't add up.

You may have a bad VLOM? They fail in multiple ways. But I'd be most interested in knowing what happens when you command the VLOM solenoids on and off at idle. You should create a dead misfire as you go down the line. The trick is to monitor oil pressure at the same time, if possible. A significant dip in oil pressure on one cylinder or another would suggest a leaking VLOM gasket.

From what i found you may want to check your oil level if it is low it can cause this code. The other thing would be to check vvt solinoids and the circuit to those solinoids for corrosion or bare wiring etc.
Also valve adjustment could be a possiblity as the valves should be fully closed when the cylinder deactivation is started. If they dont close all the way it will cause this code as the gases left in cylinder are used to balance the rotational harmonics.

The oil level is fine, the VLOM solenoids click when commanded via my Modis. One solenoid does not pull the supply voltage down to near 0, so I believe it has a bad solenoid but I don't want to replace an expensive part without being 100% sure. I want to do an Ohm test but the connector is almost impossible to get to without removing the intake.

Thanks for the valve idea, I did not think of that. I read what theory and operation I could find regarding the VLOM system.

What voltage did it pull down to, exactly? Where were you taking the voltage measurement? PCM?

If it didn't pull all the way down at the VLOM, that leaves the control wire and the PCM. If you were at the PCM, then that suggests the PCM driver isn't pulling it all the way down. A VLOM solenoid problem won't cause a voltage drop reading at the PCM connector.

Tyler wrote: ( A VLOM solenoid problem won't cause a voltage drop reading at the PCM connector.

Exactly, the voltage drops showed good working solenoids but the one that didn't drop should be suspect. I want to do an ohm test but the connector is impossible to get to without removing the entire intake.

Can a solenoid click but be bad much like a relay? All solenoids will click but only one failed the voltage test.

RaptorUnit17 wrote: Exactly, the voltage drops showed good working solenoids but the one that didn't drop should be suspect. I want to do an ohm test but the connector is impossible to get to without removing the entire intake.

Can a solenoid click but be bad much like a relay? All solenoids will click but only one failed the voltage test.

If the solenoids are common +12 V feed and individually ground side switched by the PCM you can ohm them out like this. Pull the fuse feeding them and connect one lead of your DMM to the fuse terminal feeding them. Touch the other lead to each solenoids ground wire at the PCM.

And yes solenoids can click but not be working properly.

Matt T: Thanks, I was wondering about that but was worried about other components being on the feed circuit.