2018 Infiniti Q50 3.0t LUXE RWD - DAS - Steering issue

Hello everyone,

This may be an advanced troubleshoot but I cant think of a better place to find some answers then here...

If I have learned anything from this site, it is the importance of a good diagnostic procedure so let me start from the beginning and hopefully someone here may be able to offer some collective brainstorming and help me find a solution.

I purchased a 2018 Infiniti Q50 LUXE RWD with a rod knock.  I knew it was going to need an engine so I offered the person $5k for the car (it is in good condition, owned by an elderly lady so it wasnt molested with a bunch of aftermarket hackery) with the calculations for a motor replacement.  I test drove the car and it drove fine, just had that familiar knock sound once the motor was above idle speeds with a load. When I went back with a trailer to get the car i noticed that the steering was very heavy (like no power steering).  It wasnt that way when I test drove it so something clearly changed in that time-frame but the car couldnt be driven so I asked the owner what they did and they said the only thing they did was drop the oil pan to have the dealer give them an assessment about the knocking noise.  I did notice it had a dead battery and it looked like they completely removed the battery and was starting it from a jump box while trying to sell the car.  Since I was already there with a trailer i took the car anyway hoping it was a fuse or something along those lines.  This vehicle does have the DAS (Direct Adaptive Steering) or steering-by-wire system so i was hoping this would be a fuse but once I got it home and had a replacement motor installed and installed a new battery found that the steering heaviness was still there..

We checked all three fuse locations (drivers kick-panel, engine bay fuse box and battery post fuses) and there are no lights on in the dash and after scanning the car there are no codes being thrown from the main system.  When the car is up in the air, once you start the car, the steering wheel turns all the way to the right by iteself and you can feel the steering is very heavy.  My scanner was not able to perform a DAS recalibration so I took it to the Infiniti dealer and prayed they could simply recalibrate the steering system.  I got the dreaded call where they said sorry, they couldnt recalibrate it and after their diagnoses was completed they told me that the steering rack had an internal failure and the whole assembly would need to be replaced.  Final cost would be over $5k of course.

I have already had a bad experience with this dealer in the past and dont have a lot of faith in there diagnostic skills so I am stuck trying to read through all the "noise" and try to find the true problem.  Maybe it is the whole rack but it seems suspect so I am hoping someone on here may be up for the challenge and help guide me through a comprehensive test procedure so I dont throw a ton of money at this and become just another parts changer.

This forum was very helpful with another electrical problem I had with my Red Sport 400 Q60 so I am hoping we can figure it out together.  Unfortunately, I am already into this vehicle by over $12k now with the purchase and motor replacement so if I cant find a way to get this fixed for a resonable price, I am going to be under water so my fingers are crossed.

I have some skills, tools and a ton of perserverance and realize this may be a little more on the advanced side, but hope someone is willing to pull me under their wing and see if we can figure this out.  I understand the DAS system is on the complex side but I am willing to put in the time if anyone feels up to the challenge.

Things I know:

There are no active codes or lights in the dash
The steering wheel will turn by itself all the way to the right when you start the vehicle (if the front end is up in the air) so it appears there is a sigal telling the vehical to turn right
I have confirmed all three fuse locations are good and have power (consistent with no CEL lights on the dash no codes in the computer)

I have a Torque V scanner with oscilliscope and a decent set of electrical diagnostic tools (test lights, power probe, scope, etc) but it looks like I need to renew my license for the scanner so that is going to cost some cash but it was updated a year ago so I am hoping I wont have to do that unless needed since I may need to buy a new steering rack in the future.

Anyone got any ideas of where to start?  I have no idea where to start but if we can at least confirm the dealers assessment is accurate, I will feel better about buying an expensive steering rack.  I am going to put the car up in the air tomorrow and start inspecting wiring for anything obvious but maybe someone on here has some experience with isolating the circuits of this system to help me confirm the issue, maybe even know a test procedure to zero in on the actual failing part?

Thanks,
Kevin 

Hey Kevin, welcome back!

Unfortunately, I have zero experience with the DAST system. The DAST wiring diagram looks like a real mess, too. 

No offense, but are you sure you did attempted the DAST calibration correctly? From what I'm reading, it's not a simple magic button pressing procedure like we're used to. The amount of work involved makes me question if your local Nissan dealer actually attempted the calibration during your last visit. I know I wouldn't be thrilled about doing that whole song and dance as part of a diag.

I attached the 'Work Procedure' and an associated TSB for reference.





I don't know the Launch software well enough to know if it'll do all of these steps, but it's worth checking, IMO.

The alternative would be to get Consult 3+ or Consult 3+ R2R. Check out Nissan Techinfo for details. However you do it, you'll need some way of completing the module programming and Work Procedure if you do end up replacing the rack.

Thank you for the response.

I was not able to get any connection with my launch scanner and assumed it is becuase my license has expired, it is pretty expensive to renew so I decided to let the dealer attempt a recal. they tried and said it would alwasy go back to the same behavior (the wheel turns all the way to the right).

I was a little concerned about the quality of this dealer because of my last experience but I have no real way to confirm if they performed the process correctly.

They told me my rack was malfunctioning and i needed to replace it. It is $3400 so I wish I had a way to confirm. I have a RS400 with the electric rack so I was hoping I would be able to confirm somehow before just throwing such an expensive part at it.

It definately has power because it turns the wheel to the right but doesnt seem to identify or find "center". The infotainment console has some performance interfaces and one of them shows the position of the steering wheel and if I fight the tension and move it through the range, I can see the steering position in the console move from left to center to right so it seems like something is telling the rack to move to the right.

I was hoping someone on here might have a clever idea. Maybe someone will chime in at some point or I may just need to throw thousands of dollars at it just so I can try to get some money back. I have $13k in it and for what the dealer is asking to replace the rack it will take more money than the value of the car, definately a net loss.

Thanks again and fingers crossed someone chimes in with some feedback...

I just read an article in Decembers Motor Age Magazine by Brandon Steckler working on a different car with the same problem.
www.vehicleservicepros.com/service-repai...ronic-power-steering
It was a Lexus/Toyota that would turn full right when keyed on with the wheels off the ground.
He showed all the scope captures to show that it was the steering input sensor lying to the module, but none of it really mattered because everything is built into the steering rack and the whole assembly needed replacement.

Thank you, that would be consistent with the dealers assessment.

I struggle to understand why the time tested steering solution was not enough and justifies this Rube Goldberg monstrosity...

Really appreciate the information. Wish I had a way to reset that module.

You will need to consult 3 for this. I had a similar issue. If recalibration will work, it will work with consult 3. I had to hire a company called "Scan on Site," aka SOS in Maryland. To drop the oil pan, I assume they dropped the subframe. If they did so, check the connections for the rack and pinion. Your model should have two thick connectors for each motor and a smaller connector. You can get away with a used rack and pinion. It will also need to be programmed/ calibrated. You don't have to take out the subframe to replace this rack and pinion. A used one should cost about 500. But first, see if someone can actually calibrate it since it is a lengthy and complicated process. I have heard an incorrect attempt to calibrate the steering will damage the rack and pinion itself. This is a warning consult gives during the process of calibration.