Went out for a joy ride tonight and it ran great for over an hour. Then on the way home while coming to a stop it started to throw error messages and run very rough. We had to pull off road, turn it off, sit a few minutes and then restart. Had to do that process at least five or six times in order for it to run correctly and get us home.

Messages were Traction Control, Stability Control and Fail-Safe Mode.

I keep the car on a battery tender and everything was great for that first hour or so. Any ideas of what to check or look for? Do I just need a new battery (even though the battery seems new enough)?

 

Disconnect the tender and measure the voltage across the battery terminals after a half hour or so. You should see around 12.6 volts. Anything lower than, say, 12.4 volts and the battery is suspect.

Check for any OBD codes and post them here:- the actual codes rather than the reader's interpretation of them.

 

Classic low battery codes so that should certainly be your first port of call. How old is the battery? It will usually have a date on it somewhere. Sometimes stamped into the top of the terminal itself.

Richard

 

I ran the OBD2 codes this morning and only got P1000. I am on my way to Auto Zone to get them to check battery and maybe replace.

 

Lucas always said after standing for 24 hrs disconnected should be over 12.5v or its suspect.

 

Just returned from Advanced Auto. They put their OBD2 reader on and got the same P1000. I then had them run a check on the battery and charging system. Battery tested at 12.66v with car running. Charging system also checked out good to specs. The car ran fine on the way to and from the store...

Others have said check/clean/replace wheel speed sensors. I have not done that yet as it is very hot and humid here in Georgia right now.

 

12.66 with the car running is not optimal. It should be that reading after it has sat for some time, preferably overnight, but higher with it running. Advanced auto parts should be able to check amps "under load" as well to get a more accurate reading.

If you don't have a battery tester, take it out and let the car sit overnight. Then take just the battery to the parts store and see what it reads. If bad you are already there with the exchange unit. These cars are very sensitive to weak batteries.

 

The battery should test at 13.5 volts or higher with the engine running. Sounds as if you have a failing battery....

 

I'm not sure how the charging system could check out good to specs if it the alternator is only producing 12.66V with the the engine running as that is definitely too low.

Richard

 

I would have a hard look at the alternator. 12.66 is, essentially, not charging at all. You should see just over 14v normally, and high 13s at a minimum.

I would also trust a chain auto parts store about as far as I can throw a Jag battery. If they told you your charging system was OK at 12.6 volts running, they are incompetent.

 

Update for the day. I tried to take the car to my son's house to check the wheel speed sensors and during the 25-mile trip it threw warnings and went into Failsafe mode eight times. I finally made it and we put a reader on and drove for short while. He cleaned the wheel sensors, and they seemed fine. He checked the battery while not running and it showed 12.77. It threw a P0121 code and then Failsafe again. I called a wrecker and dropped at my local shop. P0121 is Throttle Positioning Sensor. I will update next week when I get the update from shop.

 

P0121 will give you a fault message, but I'd get definitely get the charging sorted out first, as others have suggested, as it may be a phantom.

 

I will ask the shop to test the Alternator while they have it. Yesterday's battery test was resting test after car had been shut off for at least a half hour. Tested at 12.77v. I tend to believe the Throttle Position Sensor issue as the problem. Maybe 6 to 9 months ago, the car would crank and immediately rev to 4000 RPM's and sounded bad. I would shut off immediately. Did this about three times until we unplugged the battery cables and reset everything.

I will report results when I get the car back next week.

 

Update: Just got it back from shop. They had to replace the Mass Air Flow Sensor and it is running like a top now.