A fully charged 12V battery in good condition will indicate 12.6 volts. Readings lower than this can indicate a failing battery or charging system or may just mean that more time is needed to fully charege. Voltage alone therefore doesn't mean much and a proper load test is required.

Stock alternators (I think) are at least 130 amps if not more.

The strategy of measuring system voltage with increasing electrical loads works well. I've turned everything on that I possibly can and noted that voltage remains around 13.9-14.3 at engine speeds above idle.

 

thanks for the insite in the recent posts guys.

My situation is a little different than the other poster's that had a car that went into "restricted performance". With that code, at least you can drive the car around. When I get the sequence of codes, it says "engine mangement system failure", the car idles like it's on 4 cyclinders and the idle speeds up to 1100. Pushing the gas pedal does nothing. All I can do is coast to a stop or drive around at idle in 1st gear. I have to shut it down and then restart the car. Upon restart, it'll idle and then either trip the code again or be back to normal temporarily. It also seems the longer I let it sit, the less chance of the code immediately popping up. For instance, if I immediately restart, it'll probbaly pop up again. If I let it sit for 1 or 2 minutes, my chances of it going away are better.

I'll break out the multimeter and test the battery output with the car on and off.

Yes, I'd imagine that the stock alternator is a tad small for the additional draw.. I don't think my amp was pulling nearly 75 amps when I was running it originally, but that's what it's fused for. Combined with the lights being on and stereo draw, it was probably hard on the system though.

In my opinion, the crazy thing is that the engine management system supposedly only needs 10 volts but I'm tripping it.

 

 

Get someone to read YOUR OBD II codes and post them! The stuff on the dash only tells a small part of the story. Also do a load test it is free FREE get the real info on your battery.

 

This sounds like 2 threads intertwined with cars with different issues. Not gonna be easy to make a single thread cope

 

Nobody has mentioned oil, octane or ethanol yet. Is it too late? Slotted rotors anyone?

 

I just want to chime in here with some input.

First, good job isolating the amplifier by removing the fuse you would be suprised by the amount of people that can't do this.

As far a people recommending that he just buy a bigger battery or a certain brand beacuse of the system draw, the only thing this really does is give you a longer reserve of power with the car not running. It's a band aid over the real problem.

If the system is really drawing more than the alternator can produce the only real solution is a larger alternator.

Now beacuse music is dynamic, with dips and valleys in the sound most cars don't really need an upgraded alt. unless you listen to your music 24/7 at an extremely loud volume or are playing test tones.

The first steps are to make sure the power connections from the battery to ground, engine block to ground, and 12v + from the alt. to the battery are all up to par. I have seen lots of cars where these are corded and cause power drops.

I personally have stopped buying Optima since they were bought out, they just haven't been the same.

Just some musings from some one who's been around car audio one way or another for 14 years.

 

Hi guys,

As an update I dropped off at the car at the shop to be load tested today. When I picked it up they said that it was a ground issue and cannot figure out what it was. They were going to refer me out to a specialist. So it sounds like my battery is okay and my alternator is okay as those are the main things they checked.

The only thing that I can think of electronic that has been worked on in the last few months was my left front headlight the exciter ring was replaced. I'm not even sure if that's the correct term but it's a metal piece that the black back part of the headlight assembly Bolts onto. In addition after that repair my auto leveling headlight on the left side has not been working properly.

If I wanted to see if this was a culprit, is there any way to test or unfused the left headlight? Or are both headlights fused together?

I don't know much about ground faults so maybe somebody more experienced people can chime in. Thanks!

 

Either it is a bad ground or a fault that is grounding out I do not know. This is a little information that might help.

Link Current Testing
http://jagrepair.com/images/AutoRepa...%20Testing.pdf

 

the electrical schematic in the JTIS will show you how the headlights are grounded and where those are located. It sounds too coincidental that after the headlight repair this starts happening and your autoleveling isn't working. There is a separate motor inside the headlamp that gets power from the ballast, perhaps this connector got pulled and not reconnected?

 

Is auto leveling powered by that small harness of plugs into the black ballast of the lightbulb assembly? I do recall playing with that and making sure is plugged in when I was working with it but I don't know what they did when they repaired the headlight. If that is indeed what powers auto leveling then it probably is unplugged or not a very good connection. To complicate matters I'm working off my phone since I just moved and do not have Internet service yet

 

Well. So far I'm successfully putting some more "daylight" miles on the car woth no issues yet. I'm buried with new house projects so I'll work on it Saturday.

 

see this right here.. this right here is EXACTLY what happens with my car... the 1100rpm when on "P" (idle) is spot on!! and once again.. contrary to everybody else's opinion.. i blame the throttle body... after about 3 months of ownership my 92,XXX miles STR was doing this SOOO often i was beginning to think i had purchased a lemon.. it was seriously happening every 3 minutes.. and like in your experience, the longer i waited before starting her up again, the less likely i would be put in "limp mode" again.. after posting my symptoms on this forum.. someone mentioned how sensitive our car's TB were to moisture.. after changing the battery and cables with no resolve, i thought about replacing the TB.. until i was told it would be about a $2500 job.! so instead.. i had the TB and TBPS cleaned along with all the connections as well as the 100k service.. and WAHLAH.!! 8 whole months without it ever going into limp mode again.!! after that it limped on me maybe another 2x or 3x but of course.. only after having her washed...

...

which brings us to present day.. on Sunday i detailed my car.. i used a hose and might have rinsed her longer than i should've because since Sunday she has been limping.. too often for comfort.. on a 40 mile round trip she limped on me 4 times

its the worst feeling ever man.. the insecurity.. not knowing if or when itll strike again.. having to drive on the right-most lane in fear that shell suddenly limp and completely restrict the ability to accelerate... I Love my car.. more than any other car i have ever owned, but this problem here.. this problem here will forever taint all the great memories i have of me and my Jaguar.

END RANT\

 

Did you seal the TB connector to keep moisture out?

The symptoms show the PCM is desperately trying to keep the car running at all, despite there being one or more faults. Not long ago a car would just have quit on you so this is a step forward. Something is faulty but the PCM is just managing to keep it from quitting. Remember how with older cars sometimes you'd rev an engine to stop the car cutting out, well this is the same thing.

Here's a standard pic of the main items the PCM uses/needs, any of which may be faulty www.onboarddiagnostics.com/page02.htm
It applies to ANY modern car, essentially because the USA government mandated it. You can work your way round the items checking them out.

 

thanks for the rant. More info and scenarios is better than not hearing about it. I've actually never had an issue with my car after washing it or the rain. I guess it helps that I'm in CA and it rarely rains here during the day when I'm driving.

I'd definately like to get my tb and tbps cleaned and then sealed up. I'd imagine that it'd be good preventative maintanence as my car only has 65k. I'm going to drive it and check it out this weekend and probably drop it off at the shop Monday to fix the faulty auto leveling headlight and also have them check out their previous repairs.

 

It's just the connector that needs sealing. Not a big task!

 

Does the connector need to be sealed to prevent moisture getting in or from the elements in general? Anyone have a pic of the connector in question?

 

Unplug the plug and clean it with electrical contact cleaner and use a little dielectric grease at the contacts and around the seal of the plug. Remember no to over do the grease.

 

I dropped the car off today to have the headlight wiring checked out. We'll see what they say. Hopefully they can find it or else it's getting traded in on a new car for the wife...

 

Hi,

My STR had the same problem parkbrake failure - dsc fault - gearbox - etc and I tried everything I could never suspecting the throttle-body since it was only one year old. My engine was also revving to 4500rpm at start-up and surging dramatically with the gearbox locking into various wrong gears randomly.

Convinced I had bought a dud vehicle and feeling pretty depressed about that I eventually fitted a second-hand but known good TB and that was the end of the problem. I have driven 10k miles trouble-free since then and am enjoying what must surely be the best-value luxury performance car it is possible to buy.

Hope this helps

Good luck!

Gordon