Hi guys,

Hoping for a bit of help. Car is a 2014 L494 3.0 TDV6

After restricted performance messages the main dealer diagnosed that the car needed a new turbo. Our 3rd party warranty’s conditions meant that it couldn’t go to a main dealer for this. Car has been into a indy who has changed the turbo (including actuator etc) and replaced the manifold. Car came back and went into limp mode again. Indy took it back, found oil contamination in the hoses going to the solenoid and replaced it. Car went back into limp mode on the motorway the next day.

GAP Tool has shown the following fault throughout:

P004C-77 (6C) Turbo/supercharger
boost control solenoid B - circuit low
Mechanical failure - commanded
position is not reachable

The Indy has been brilliant to be honest but isn’t a LR specialist. None of the warranty companies approved repairers are. I’ve hunted all over the Internet and cannot find much on this fault code. Also a bit stumped given the solenoid has been replaced as well.

Can anyone share any experience or insight?

well there are 2 turbos ? maybe the other one ?

try a bottle of wynns vvt cleaner if loosing faith in garages

The Passenger side turbo is fine as the fault code and limp mode only happen when the drivers side turbo is engaged, which happens above a certain RPM threshold.

I was hoping to find someone who had experienced the same problem or who knew what the test plan is for this fault code.

P004C-77 isn't a valid DTC

If the code is P004B-77, then the following is the recommended actions



Secondary turbocharger charge air shut-off valve system mechanical integrity
Secondary turbocharger charge air shut-off valve system vacuum leakage
Secondary turbocharger charge air shut-off solenoid failure

Disco_Mikey wrote:

P004C-77 isn't a valid DTC

If the code is P004B-77, then the following is the recommended actions



Secondary turbocharger charge air shut-off valve system mechanical integrity
Secondary turbocharger charge air shut-off valve system vacuum leakage
Secondary turbocharger charge air shut-off solenoid failure

@Disco_Mikey really appreciate your input. What do you mean by it not being a valid DTC?

This is the code being displayed by GAP Tool and is DTC quoted on the initial main dealer report. See below:

Click image to enlarge

Any help ?

Click image to enlarge

Col, my Topix didn't list that fault code

Mikey,

It did come from a L320 list but as it's a 3.0L assumed it probably applies to a L494 as well, but may well have it wrong there, issue date on the page is May 2019.

Cheers
Col

Col wrote:

Any help ?

Click image to enlarge

Cheers
Col

Quote:

The engine control module is unable to command a motor, solenoid or relay, to move a piece of equipment to the commanded position either due to a failure in the actuator or its mechanical environment

Harness failure - Variable geometry turbine vane actuator control circuit short circuit to ground, high resistance, open circuit

Harness failure - Variable geometry turbocharger sensor circuit, short circuit to ground, high resistance, open circuit

Mechanical failure on actuator mechanism

Variable geometry turbine vane actuator control unit failure

Found it this time

Was it a new or recon turbo fitted?

Thanks very much to you both for helping me out.

So dealer checked the wiring and found no faults before specifying a new turbo was required. Original turbo and actuator assembly was reconditioned and tested by a specialist (The Turbo Guy in Glasgow) before being fitted by the indy (could have been a different turbo that was already recon’d and sitting on a shelf but not sure what difference that would make) Then he replaced a solenoid that had some evidence of oil contamination in the vacuum pipes.

Pipe work has all been smoke tested for leaks and none found. Im severely out of my depth here technically but is the “actuator control unit” something separate from the actuator and solenoid themselves?

Originally there were two fault codes. The one shown above along with the following:

P2263-22 (EC) Turbo/supercharge boost
system performance - General signal
failure - signal amplitude>maximum

This one is now gone after the replacement turbo was refitted. Warranty Co (RAC) doesn’t cover a brand new turbo hence the recon. Obviously, the replacement turbo being duff is something we’ve considered but hoping to exclude everything else before investigating that.

As the control module has a stepper motor in it, I was just wondering if it needs calibrating in some way if it has been replaced, I think Disco-Mikey may be the person most able to answer that though.

Click image to enlarge

Everything points towards a faulty actuator...

Being a recon unit, and having had issues in the past with duff recons, this is where I'd start

That said, there is a calibration procedure for fitting a new actuator/turbo

Ok. No calibration procedure has been carried out on the car. The mechanic mentioned that there might be one but if so he needs to find out what it is. Is the calibration procedure something that’s done on the bench? If so I believe that the Turbo Guy is supposed to have done all this.

Is it likely that the fault code above would be present with (an otherwise fine) but uncalibrated turbo installed or do you reckon that the most likely cause is that the new reconditioned turbo still has a faulty actuator unit attached to it and we might be chasing ghosts?

Calibration is done via diag, with the unit fitted to the car

Start there before chasing further