2009 MKS dies while turning steering wheel

Gregory Owner/Technician Florida Posted   Latest  
Unsolved
Driveability
2009 Lincoln MKS 3.7L (R) 6-spd (6F50) — 1LNHM93R39G604261
Dies When Turning Steering Wheel

I have this car that at idle when turn steering wheel it dies. No codes. Checked T/B to see if dirty, looked ok for condition of car, cleaned it any way, no change. Looked at power steering switch it has no change when wheels are turned. Unplug switch car will not start. Check ground circuit of switch and 0 ohms, did not VD the circuit. I can ground the circuit and car will start and stay running while turning wheels, Hook switch back up and car will die when wheels turn. Can not help to think that the computer is some how grounding through the P/S switch and when the wheels are turned the switch opens up and looses ground then dies. This is a very odd one,. Any ideas of how to go about diaging this think? I am leaning to an internal issue on the computer but dont want to pull that trigger with out some sort of proff.

Gregory …

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Brandon Diagnostician
Arizona
Brandon
 

From what I understand when the engine is running the switch should be grounded, and when it loses the ground it should kick up the rpm

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Gregory Owner/Technician
Florida
Gregory
 

that is how it is working, I think the diagram is showing the switch normally open but it is closed

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Brandon Diagnostician
Arizona
Brandon
 

What king of voltage is on the wire that runs to the pcm? Bias voltage ? Also have you load tested the ground side? I noticed the description operation is different from the diagram.

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Gregory Owner/Technician
Florida
Gregory
 

I have not lookd at what kind of voltage is on the wire when not hooked to ground, have not had time to look at it today.

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Brandon Diagnostician
Arizona
Brandon
 

Have you had a chance to check voltage on the connector unplugged and plugged in?

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Gregory Owner/Technician
Florida
Gregory
 

KOEO switch plugged in have ground, switch unplugged have 7 volts. I am looking into what voltage is supposed to be there Thanx

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Brandon Diagnostician
Arizona
Brandon
 

If it doesn't carry current with a test light I'd say it's bias voltage

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Brandon Diagnostician
Arizona
Brandon
 

Is it 2 or 3 wires?

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Gregory Owner/Technician
Florida
Gregory
 

2 wire

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Richard Instructor
Florida
Richard
 

If you take a look at the wiring diagram you can see the switch is a two wire switch that is normally open and closes when pressure increases. So when you ground the circuit, the pcm is doing what it should by keeping the engine running. When you hook the switch back up and turn the wheels and the engine stalls, what do you think is not happening? Either the switch isn’t closing or you have a…

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Gregory Owner/Technician
Florida
Gregory
   

The diagram is wrong in that it shows the switch normally open, it is normally closed and when pressure hits it opens, Can you explain why the car will not start with the switch unplugged? Car will only start when ground is supplied to the switch circuit or the switch plugged in.

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Cody Diagnostician
Missouri
Cody
   

Looking at the diagram( yes i agree the ps switch in your case is normally closed an will open with increased pressure), if the engine won't start with switch unplugged , starts with it plugged in, but dies when you turn the wheel , I would begin to think you have voltage backfeeding through the ps switch circut , most likey because the G102 ground is corroded or broken and other components use…

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Gregory Owner/Technician
Florida
Gregory
 

I have checked the ground. G102 is the main ground for PCM and pretty much every ground for the PCM goes throu it, including the PS switch. I even went and supplied a new ground straight to battery , that did not help.

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Gregory Owner/Technician
Florida
Gregory
 

The diagram is wrong, the switch is normally closed and opens when pressure is present. The car dies like the key is turned off, there is no struggle like the idle not raised quick enough. Even when the rpms are up at 2000 when the wheel is turned the engine shuts off.

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Geoff Diagnostician
Hawaii
Geoff
 

either the description of operation in SI is wrong or wiring diagram is wrong. What if diagram is correct and the car has "learned to idle" with the switch STUCK closed? Can you see the PID for PSP change, when you bump the wheel left/right (just before car stalls)?

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Gregory Owner/Technician
Florida
Gregory
 

diagram is wrong as it shows normally open, it is normally closed. as soon as the steering wheel is turned the car dies like the key turned off. Scanner to slow to see if the pip changes, but did verify that the circuit opens when the wheel is turned.

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Geoff Diagnostician
Hawaii
Geoff
 

" did verify that the circuit opens when the wheel is turned" - OK. Thanks for clarifying.

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Timothy Owner/Technician
Wisconsin
Timothy
 

Put the switch PID up all by itself when scanning. That way the scanner will not have to refresh all the PIDs before it updates, it will only look at that PID and will refresh rapidly. If the PID changes, then the issue is NOT the switch but something else. The switch disconned, should not cause a no-start though…that is something I've never seen prior to this. have seen a bunch of vehicles with…

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Gregory Owner/Technician
Florida
Gregory
 

I did do that and it does show to open, goes from low to high as car dies. It is just like the computer is using the circuit for a ground. I have noticed that high idel when started is working and idle increase when put into gear. This thing makes no sense. I am still playing with it. I did run a new ground from PCM to battery on all the ground circuits from PCM and no change. Thank you

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Timothy Owner/Technician
Wisconsin
Timothy
 

Well, at this point, I'd be leaning towards a PCM issue. If the PID is reading open and closed (change of state) then the PSPS is not it. And, as I said prior, it should not cause the vehicle to not start with it disconnected.

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