Hi Everyone,
Took my 350z out for her first track day yesterday (after the car had been sitting for 6 years) and during my first session, the SLIP light became illuminated and I threw 2 codes P2128 (Accelerator Pedal Position Sensor Circuit) and P2138 (APP Sensor Performance Condition Fault).

The car went into limp mode, so I disconnected the battery for 10min and unplugged the PCV (plugged the intake female end and let the hose breath). I then went out and ripped on the car for 4 sessions with 0 issues.

I have no idea why the code was thrown in the first place, why the SLIP came on, or whether disconnecting the battery or unplugging PCV is what brought the car out of limp mode and let me complete 4 sessions with no issues.

HELP

 

Keep in mind that your car's diagnostic system is active from the minute of start-up. While I've never had those particular codes at the track (and can't specifically comment on them), the fact that you erased them and went out for another four sessions says the system did not detect similar fault(s). Typically, Nissan "limp mode" is reserved for serious codes and could be due to a drivability issue or the lack of proper feedback to the ECM. Rather than damage any critical systems, it'll give you just enough power to limp to the dealer.

I'd suggest you invest in a sophisticated code reader, like UpRev's Osiris, that'll not only pull codes from the ECM, ABS and BCM sections, but also allow you to erase them from your laptop. It's an essential tool for the racetrack IMO.

 

I can't tell you why the code was thrown but you can guess based on what they are describing and the faults listed in the FSM. P2128 (Accelerator Pedal Position Sensor Circuit) and P2138 (APP Sensor Performance Condition Fault). It looks like the ECU had a failure in reading the accelerator pedal position sensor and looking at the FSM nissan thinks a wiring harness problem/shorted sensor is most likely. If you want to learn more about the codes and possible diagnosis take a look at the FSM (EC page 641 and page 650).

As for the slip light I would guess the APP sensor is used for the traction/stability control and your TSC/VSD off light should have also been on. Again the FSM has a section describing the required sensors for the TSC/VSD. If you want to learn more check it out (BRC page 51 and page 94)

The PCV system shouldn't have anything to do with your problem. Given that it's working now I would put it back together and see if the problem comes up again.