OK so I took the car down today for a nice after Christmas drive. It is 46* out here and the roads are clear from the rain the other day. The car was up on the lift with the smart charger plugged in as I didn't drive it for the last several weeks. I put the top down turned on the heated steering wheel and the seat. Side windows up and after a slow drive warm up and the tires rounding back out I got into it a little. On my way back home about 2 miles away the instrument pod lit up with yellow triangles. The messages were : Park brake fault , Emergency brake assist not available , Gearbox fault and DSC not available . The winter mode light was on in the center console and the DSC squiggle was on in the instrument pod. There were no apparent drive issues so I drove it home and shut it down. Did a restart and same lights came on. Shut down and plugged in my OBDII reader and PO724 (Brake switch B circuit high input) was locked in but no MIS light on dash. I erased the code and restarted and no codes came up. Shut it down and re-read the OBDII port and there were no codes triggered. So I'll take it out tomorrow and see what comes up and if I get the same issue I'll call the dealer who is 75 miles away and set up an appointment. I was due for 2 SW updates so I'll get it all done at the same time. 10,800 miles and it is a CPO car as well.

 

Strange and bad time to have it happen. Has to be electrical. Did you try discounting the battery to do a complete restart? Most of these electrical problems sort themselves out after a restart without needing to disconnect the battery. Sounds like you have a persistent fault triggered that just may go away after a battery reconnect.


I also took my cat out for a run today. We have similar weather as you. Roads are cleared and any salt or stones on the roads have been washed off by the rain. My car worked flawless.

 

My thought is it's in the brake switch because it was the part that triggered the OBDII code. Once I cleared the code and did a restart the problem did not come back. I'll take another ride tomorrow and see if it comes up again.

 

I've been getting intermittent electrical hiccups too, but mine are only a reboot of the control center after I'm driving for 5 minutes. I had a west coast map in the car and put an east coast year later disk and I think it did some software updates. The battery wore out before the full 15 minute reboot so I figured that there were still some software mapping processes going on. It happened maybe five times and I was starting to get worried, but it hasn't happened in a couple weeks so I guess it's worked itself out.

I've been out of town and couldn't take the car out for the last few days, but I just got back and am taking it out for a quick stretch in a few minutes. Going to be 55 degrees and sunny tomorrow, so I might get out a bit tomorrow too. I have to get it out to pick up a repaired wheel anyway.

 

OK I just took a ride about 1 1/2 hours and at various speeds . Town , highway driving and all in Dynamic mode and at times using the paddles both up and down shifts. No abnormalities at all and the car reacted without any hiccups from 0 to 75 mph. It still amazing me on haw quick it is from 35- 75mph. I plugged in the code reader after I got home and all was clear with no stored codes. I'll keep an eye on this but my suspicions are that the car didn't like sitting in a cold garage (usually 10* above outside) but then again it's something to watch. I need to stop by a buddies place (auto body shop and NYS inspection) and put their code reader on it. That one reads all of the memory so any old OBDII codes will show up.
While I was out I stopped by one of our local golf courses that was open today. It was full so I reserved a tee time for tomorrow. This will be the last round for the year. I hope the rain holds off but what the hell , I'll play anyway.

 

Could it be that your battery maintainer overcharged the battery? You probably know more about cars than 95% of the members on this forum. Good to hear everything went while today. Hit 'em straight and long tomorrow, every year after you may not be as long.


I had my cat out for a good stretch today. What a great day for late December.

 

In the past automotive diagnostic was a learned skill both in textbooks as well as hands on. The basics of fuel and spark are still there but now microprocessors are in the middle. Another part that also complicates it is software. I've had a lot of sweat and fun working on cars/trucks and now it is interesting to get into the ECM stuff. Although we think OBDII made things easier I think it took the learning part of the job out and now a lot of techs are just parts changers. Now the SW adds to the problems with either a boot up issue or an intermittent sensor . So my advice is everyone should get a cheap code reader and when that MIL shows up find out what you got. Also I believe when you get the car serviced tell the dealer you want all of the bad parts before they start the work. As for my problem I don't think it just went away but we'll keep an eye on it. Enjoy your drive .

 

61 degrees in Virginia yesterday, I had the top down. I did a lot of work in the yard, worked up a good sweat, then drove down to the garden center with the top down and it cooled me off nicely.

 

Question:
Do you leave a code reader attached to the OBD port at all times?
My dash went nuts last September while the car ran fine.
Finally pulled my blue toothed OBD reader off the port and have not seen the problem since.

V

 

No I use the BT one with Torque pro periodically only to check water temperature. I also have a regular code scan tool which I use as a check. With that one you do not start the engine in order to read codes. It also has an erase feature. Just another point , the BT adapter I purchased has a switch on it so if you do leave it plugged in you can turn it off.

 

I suspect that was my problem yesterday.

Had a lunch time appointment, and was doing some 'spirited driving' on my way there, when my CEL came on.
Same thing happened a couple of weeks ago (also during some driving that cause high revs), and I had gotten a wifi OBD reader then (since I have an iPhone), and found code P0128 (thermostat under temperature), which I cleared to see if it would happen again.

I suspected that's why the CEL came on again yesterday, so since the reader was still plugged in, I reached under the dash to turn it on. Figured my phone would have the wifi connection by the time I reached the next traffic light and I could check the code. But before I got there, wow! It was like July 4th, lights flashing bells ringing... WTF???

I turned around to head to the Jag dealer I just passed a couple of minutes ago, but changed my mind and proceeded to my appointment.
After the appointment, I turned on the car and OBD reader, and saw a bunch of codes, including my suspected P0128. Noticed several of the codes referred to 'A' or 'Bus A', so I'm guessing (purely guessing) that the OBD reader introduced a signal or load onto 'Bus A', interrupting the normal signal flow and setting off the fireworks.
I cleared the codes, and pulled out the reader. The rest of the day and evening were uneventful, but I was light on the throttle the rest of the day.

Having had the P0128 twice now, I need to order a new thermostat (I'll actually order the whole assembly, as I've read about the problems with that plastic housing on the NA engines), and then either give it a shot at replacement, or take it to an indy to do it.

Thanks for reporting your possible issue with a plugged in OBD reader, as it fits well with my experience.