Hey all,
Now I am on my laptop I can reply properly.
I used to work at the manufactures of ther EPS System (TRW Automotive), where I worked in the Warranty Department analysising all UK and a percentage of international Warranty Returns to improve Manufacturing of the product. I also did some dealer visits and vehicle investigations in my time aswell.
So basically, I know everything there needs to know about the Nissan K12 EPS System.
You are correct, you cannot fit a second hand unit to a vehicle because the system handshakes with a dongle to the BCM and restricts ignition on if the dongle does not match. I know people who have fitted second hand units to their vehicle and it's worked, but not sure how they did this (I do have my opionions how you could possible do this but wouldn't want to broadcast on an open forum - becuase I am not total convinced and never tried it). I don't think TRW ever released the knowhow on clearing the dongle, when I visited Nissan Technical Centre to do some testing on a vehicle - not even Nissan had the ability to clear the dongle on the EPS System.
Next Subject, Fault Codes. The System has many internal fault codes which only display to a handful of DTC on the vehical. If the system identfies a failure it will generate a internal fault code and reduce the asssistance to 0% by disengaging the moter relay for safey. On ignition cycle the fault will be cleared unless it's a hard failure and the fault code will regenerate. If the fault code is generated 3 times in a row then the system latches and generates a System latch and can only be cleared by a diagnostics machine over CAN. These fault codes are Level A, Level B and Level C failures within the system. Level A Failures are normally CAN Issus (Communication Protacol), Level B are hardware failures and Level C are Latch Faults.
During the production there were known hardware and software issues within the system which was resolved during manufacturing. Earlier Systems are more common to fail then later systems. Software failure are normally intermittent and fails but when cleared would normally not fail again.
The system is designed in 3 blocks, ECU, Motor and Torque Sensor. The Motor was manufactured by Globe Motors and are very reliable apart from the Relay that is fitted. The Torque Sensor is an optical system produced in a clean room environment and the ECU was manufactured internally by a sister plant. I wouldn't recommend anyone trying to repair or opening the system without knowning what they are doing. I have questions a few of the re-manufacturing companies that state they repair the systems asking what exactly do they repair (just out of interest) but never got a reply. I would really question their intentions because I know TRW would never release the source Code or Database Files for any external site to repair the EPS. I was working in Prague for 1 year to estblish a Re-Manufacturing process for the EPS Systems and to be honest, it never hit off due to safety and the manufacturing plant didn't want to release the source code - it's agood job I had all what I needed! TRW always said that no system would ever be released if a Failure ever occured regardless of cause; I remember we had a production failure where the test machine was created internal fault codes into the system and all the systems were scrapped (over 200).
The system works on the CAN System of the vehicle and transmit and receives data to and from the ECM, BCM etc.. The system can be interigated with TRW mapped databases and internal parameters can be monitored and configurated over the CANbus. This was never released (as I'm aware) to the general public or Nissan.
Unforntunatly TRW lost the contract for the K12 system in 2009 (I think - if I remember correctly) which was unforntunaity becuase by 2006+ the system was really good and I would recommend the system to anyone. I beleive Delphi now produce the system for the K13 and also a retro fit for the K12 for the TRW replacement. I left TRW in 2010 and went on to bigger and better things.. but I do still know alot about the system and could really help someone if needed with reading the internal fault codes and resetting the dongle if required.
Another thing that I didn't talk about - The system has diffenrent Tune data for different Car configurations, without reading my old notes this was, Perol, Diesal, Sport and C+C Model Range. The system has boost curves, self steering centring and all the good stuff which can be configured with the right tools.
As someone said above, the system does have 2 relays, These are actually called a Link relay and Motor Relay. The Motor Relay is to activate the motor, and to disable the 3-phase motor on failure if required. The Link relay is on the ECU.
I'm trying to answer all the questions above with alittle of information, faults can be caued due to the relays but it's just as likely to be an internal hardware failure. a spec of dust in the torque sensor or a software issue. As I said previously, the system has many faults ( i think around 130ish) and these are assigned to about 5 DTCs so therefore the below DTC might have 100's of root causes. i.e DTC 5606 might be due to the Motor Relay, or the FET Drive for the Mototr the hall sensor which monitor the Motor or the motor feedback circuit. So basically could be either Motor or ECU Fault - in Warranty we barely looked at the DTC unless the system had no internal fault codes because it never helped!
DTC Number Description
5601 Battery Voltage Fault
D000 CAN Bus Fault
5609 CAN Vehicle Speed Fault
5611 CAN RearGearEngaged Invalid
5603 EPS Transient Fault
5604 EPS Operation Fault – Torque Sensor
5606 EPS Operation Fault – Motor
5607 EPS Operation Fault – NVM
5608 EPS Operation Fault – ECU
5604 EPS Internal Fault – Torque Sensor
5606 EPS Internal Fault – Motor
5607 EPS Internal Fault – NVM
5608 EPS Internal Fault – ECU
If someone needs specific details then private message me and I'll try and help.
The TRW System does get some negative feedback - but to be honest I like it. I like it that much I have fitted it to my kit car, this maybe because I can get it working and do some fancy stuff with it - but it's worked really well..
I think I have answered as much as I can - my wife is giving me that look to get off my laptop.
If I can post other helpful stuff I will.
P.S I live in Birmingham - UK so if anyone is around I'm sure I can help. I actually went to a scrap yard yesterday and got 2 EPS off a Micra for spares for my kit Car, knowing if it fails it easier to chnage it. Only takes 10 minutes to remove the EPS (from a scrap car) the bottom of the dash does get in the way and I break it on the scrap car!!!
Hope it made sense and everyone gets alittle information.
Jason