Help with code P1990

[Desflurane 4u]

Car is a 2011 997.2 with PDK.  So I go out to the car after it sitting all day, on level ground don’t know if that matters, and put it in drive.  Car doesn’t ease away, smooth clutch engagement, like it normally does.  Kind of feel like someone learning how to drive and sort of letting the clutch out too quickly.  So, I stop and it does the same thing.  I go on short drive and car won’t shift out of first gear but the gear display on the dash shows it in second, but it never shifts.  So I try to put car in reverse and it won’t go into reverse.  I try paddle shifters as well as manual shift lever but it won’t shift out of first or go into reverse.  I turn car off and it shifts perfectly and smoothly.  Pull codes with a fox well OBD scanner and get a P 1 990  DTC - Positive engine torque intervention not possible.  Can someone please shed some light on this for me. First time I’ve had this code.  I do have the following codes that are chronic, C152 DTC-communication PSM control unit (drive),  C150 DTC-Communication DME control unit (drive), 8005 DTC-Terminal S Upper limit value exceeded. Car runs fine and I’ve had no issues at all except today. The chronic codes have been present for months. Thanks for the help.

[Loren]

 

P1990 PDK Software monitoring A (or B) of signal processing unit

Possible fault causes:
- PDK control unit faulty

 

Fault effects:
- CAN alive counter freeze
- Engine speed limitation
- Transmission limphome indication in instrument cluster control unit

 

C150 DME control module, communication

Possible fault causes:
- No power supply for DME control module
- DME control module incorrectly coded
- Short circuit or open circuit in the CAN drive
- DME control module faulty (in most cases the cause is not the DME control module but incorrect coding!)

 

C152 PSM control module, communication

Possible fault causes:
- No power supply for PSM control module
- PSM control module incorrectly coded
- Short circuit or open circuit in the CAN drive
- PSM control module faulty (in most cases the cause is not the PSM control module but incorrect coding!)

Unless you know of some circumstance that may have affected these units (damage from accident, flooding, accidental short circuit, ... or even mice damaged wires) then you will likely need a Porsche PIWIS tester to run further diagnostics and re-programing.

 

[Desflurane 4u]

Loren,

 

Thanks for the response. It looks like the CAN drive is the common denominator in all three of the codes, except the transmission code.  Looks like this is beyond my pay grade.  So I will have to bite the bullet and take it to a dealer, which is 2 1/2 hours from my house.  Also do you have any idea if the PDK control module is inside or outside the transmission? Reason I ask is that is if it’s inside the transmission, it basically totals your car as it’s $20-$25k to replace the unit from Porsche.  Also it seems weird that the car would loose it’s programming but I guess that sort of thing can happen.  Thanks again for the help.

[Loren]

Yes, the control is inside the PDK. Likely best it be checked with a PIWIS.

 

[Desflurane 4u]

Drove it to work and back, about 30 miles no issues.  Just dropped it off at the independent shop as Porsche is 2 1/2 hours away.  I’ll keep everyone posted.  Just a side note, not sure if it’s related, but the dash display that shows what gear the car is in has never shown R for reverse.  By the way, the pdk control unit looks like a valve body with solenoids.  I’ve seen this part on eBay for $1750. Any knowledge of this part being of decent or bad quality?

Edited January 4, 2021 by Desflurane 4u

[Desflurane 4u]

So I took the car to an independent shop, left it overnight and picked it up today.  Indy shop tells me that they saw no codes at all in the car. So I go home and hook it up to my Foxwell scanner that I got on Amazon. Car has all the codes that were on the car when I brought it to the shop.  The only saving grace is that I had them reset the maintenance required light, which they were reluctant to do.   Cost me $125 to have this done. I guess it’s not a complete loss as the maintenance required light is now turned off.  Still have the can bus faults present.  I’m sunk as I have no idea as to how to trouble shoot the can bus and the only shop in town that does European cars apparently doesn’t know either.  Anyone have any ideas on what to do?

[JFP in PA]

That is because you need to have access to a Porsche specific scan tool like the PIWIS Porsche factory tool; a "global" European scan tool won't be able to access this system, and won't see anything wrong.  Some independents have this tool, all dealers have them.

[Desflurane 4u]

Yes, I specifically asked if they had the scan tool that will access before I brought it there and of course they say yes.  Funny that my cheap scan tool will do they job and theirs won’t.  At least they reset the maintenance required light.  Frustrating as heck!  Is there any way I can diagnosis or figure out what is going on with the CAN?  I assume it’s some sort of computer that processes information from various sensors.

[JFP in PA]

You CAN Bus system is how various systems communicate with each other.  Sometimes the individual modules lose contact and need to be reset to work properly, which again requires a Porsche specific diagnostic tool.  While there are are some aftermarket diagnostic tools that can "see" a fault, like yours they typically cannot communicate and reset the system.  This is the unfortunate state of automotive diagnostics, the OEM's are required by law to allow some systems to be accessed by third party diagnostics tools, but many component's are "walled off" and require very specific tools to work with them, in a vain attempt to secure work for their dealer network.  Law also requires the OEM to make their factory diagnostic systems available to the aftermarket; in Porsche's case, their PIWIS system is only available for lease, with the first year costing around $20,000.