P0502 Help!!

[jstatham]

Well no luck. I hooked up the tech 2 and less the 2 minutes into the Evap test I get conditions failed. I pulled the codes and guess what a P0502. I checked and rechecked the wiring and everything seems fine. I think its down to the speed sensor or the ECU. I ordered a GM speed sensor just to test the resistance. The thing I don't understand is the service data calls for 1300-1500 ohms resistance on terminals 71 and 72 which connect to the sensor and all the sensors measures over 1800. I have tested 4 different aftermarket sensor at a few different part stores. Beyond frustrated is an understatement. I don't think the the tech 2 saves data while running the Service Bay Test. It is failing while idling at 2000 rpms like the test wants you to do. The VSS is registering 0 because its not moving. If not running the test it never kicks the code. My tag has already expired so I need to figure out how to set dang evap so I can get an Emissions.

[gtstorey]

Typically, the ECM saves freeze frame data when it throws the code. But it's not something I have ever used much so I don't know the extent of what it will save.

I'll try and reread the conditions for running the P0502 check this evening and see if that jogs something. I don't remember anything about the car having to be moving, but maybe that is assumed.

You might get your ECM reprogrammed back to stock using SDS.

[jstatham]

I talked to several shops and decided to go back to the way it was before all this started. I put in the original Speed Sensor and the Original 02 sensor. I then drove it around and got everything to reset but the evap. I am going to try the test tonight and see what happens. I doubt this is going to change anything but who knows. Fingers crossed.

[gtstorey]

I checked the conditions for running the test and nothing stands out. It doesn't mention anything about the vehicle actually moving, but probably a given. Set for P0502 is confirmed as transmission output speed of 58 rpm or less for 5 seconds. There does seem to be something left out of the manual since you could meet all of the conditions to run and set the code in normal driving except maybe the requirement to run the test of engine torque between 50-6042 lb ft. Maybe it doesn't expect torque to get above 50 lb ft in neutral.

[jstatham]

Well last night I put back in the old 02 and the old speed sensor and the test ran fine. I screwed it up at the end and hit enter before I turned the engine off but it ran. My questions is how in the world can an 02 sensor cause the Evap test to kick a P0502. I am going to rerun this weekend and hopefully get everything to pass.

[jstatham]

Last night I was finally able to run the evap test successfully and now everything is ready for the emission test. I am going to take it tomorrow and fingers crossed it doesn't kick a code before I get there. If anyone has to run the EVAP test in the future here are some tips. Choose Chose Diagnostic->2011->Passenger Car->Cadillac->D->CTS->Powertrain->(P) 6.2L V8 LSA->6 Speed Automatic->F0: Engine Control Module->F2: Special Functions->F4: Service Bay Tests->EVAP System Bay Test

** I could never get the test under the Camaro to finish the test***

Basically, after the Tech 2 has read the info it needs and validates you can proceed with the test, it will guide you step by step.

After you've chosen the EVAP Service Bay Test, the Tech2 begins the prompts:

First, you'll be told to leave the ignition key off for 10 seconds (you have to count that out):



After that, you'll turn on the key (but don't start the car). Once the Tech 2 has read the Data port, it will prompt you the EVAP test can start (or NOT) and to start the car, idle between 1800-2200 rpm (steady!) and then press [Enter] to begin.

Once you press [Enter], you need to maintain 1800-2200 RPM for about 6-8 minutes (it has a counter) and it will perform a series of EVAP tests (11 data points are watched). You'll hear the Solenoid working and seeing the '%'.

After about 6-8 minutes @ 2000 RPM, you'll be told to take it for a drive. then press [Enter] to start the drive test.

The Tech 2 shows 15 KM and 600 seconds to do the drive -- don't worry about the seconds, the KMs are what's important. Time will likely expire before the mileage step is completed.

After you've reached '0's, you'll be told to return to the 'Service Bay' for engine off EVAP Test.



turn off the car (just turn the switch 1 click until the engine is off then do not touch it) and press [Enter] to start the engine off test. This test will take about 5 to 10 minutes (and yes, you're in the car and waiting -- @ least I did). You see the Fuel Tank voltage change and here the solenoid working. Once you've waited, the Tech 2 will show you your status:

Overall it takes about an hour to do the Engine On, Drive, and Engine off EVAP Service Bay Test.

I stole the notes above from another post but a few things with the engine off test make sure you turn the switch 1 click and do not touch it. I believe this was causing me issues. It took me about 5 times to get it to pass. I am still floored on how the new O2 was causing the speed sensor code when running the test. I hope to report tomorrow a successful emission test.

[gtstorey]

are the o2 and VSS in the same harness under the car? Maybe damaged wiring that was moved swapping the o2?

[jstatham]

They are not on the same harness but do run close to each other. I believe they all share the same ground. It is ironic I put the old O2 back in and it all works again. I am wondering if the tune has something to do with it.

[jstatham]

Success. I made it to the emissions and finally passed!!! The moral to the story is it keep your battery on a tender.

[gtstorey]

Originally Posted by jstatham

They are not on the same harness but do run close to each other. I believe they all share the same ground. It is ironic I put the old O2 back in and it all works again. I am wondering if the tune has something to do with it.

I don't see how a "tune" could cause this unless someone has hacked into the base code of the ECM. Not really anyway that the tables in HPT could cause this unless there is just a bug floating around in the background.