So I have only had my 03 S-type 3.0 for a month. After 2 weeks my ABS light comes on intermittenly and there is a dsc not working light these would come off and on from time to time. Today there was a transmission fault light and the transmission would jerk really hard when I put it in reverse. It seems that it would take more throttle to get it moving from a stop as well. What could this be? I have read on here that these things can be electrical nightmares or is there something majorly wrong (mechanical)? So after parking it in my garage I decided to put white paper on the ground to see if there are any leaks. I went back out to move it and The tranny fault light was off the engine light was on but the tranny seemed normal.... WTF is going on???? Thanks so much for any help!!!

 

I would have fault codes pulled, to see whats being affected by or what is wrong.

 

Are you 100% and I don't mean 99.9% sure the battery is OK? Do NOT rely on old-fashioned tests or "it always starts". Those are no good for modern cars stuffed with computers.

Search on here will get you lots more.

 

Agreed. You've described some classic "dying battery" symptoms in these cars....

 

Where in Utah? I lived in Ogden for a number of years....

 

So update I just put a new battery in and abs fault, dsc fault, transmission fault, is still there and the transmission is stuck in 2nd or 3rd it never shifts no matter the rpm's and jerkes hard when going to reverse or drive. Any more sugestions??? Oh yeah I live in South Jordan about an hour from Ogden.

 

This sounds very major?? I would carefully check all the fuses and relays. Your 2005 S Type has 3 fuse boxes. One under the hood, one in the trunk spare tire area and one in the passenger side foot well. It is unlikely that everything went bad at once. You had a suggestion early on to get the codes pulled. Any luck with that? Otherwise you will need to get it to the dealer.
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So I put the new battery in it and the tranny fixed itself after 20 min of driving. You guys got me thinking of the low voltage so I drove to the parts store to have them check my alternator they said it is supposed to register 13.5 to 14 volts under normal load the voltage was 13.25 and under extreme load it was 12.95 could this be my problem? What voltage is the minimum to operate correctly in these beutiful but PIA JAGS? I ordered a new ALT but it won't be here till thursday... I wish I could get one tonight. I will however check all the fuses and relays tonight. How do I check a relay?

Used my neighbors Snap On Scanner no codes!

You guys rock thanks for the help.

 

The voltage measured at the alternator should remain level regardless of load. Some may refute this though. Replacing the 8 year old alternator seems a good idea anyway.

 

+1 on that...

Also, as long as the faults start to clear themselves you should not have to worry about any of the relays.. When voltage drops in these cars the computers start to act up all crazy. Call them "ghost faults" so to speak. They are not true so all should be fine once the electrical current flow is sorted out. Some of them may take a little bit to clear. You need to give the computers time to relearn and sort themselves out. Once you change the alternator, take the car for an hour drive and see if things aren't all clear by then. Also, while your waiting for the alternator, it may be wise to invest in a scanner of your own.

 

Check the workshop manual (ebay $10) for the voltages. At least on mine the PCM controls the alternator voltage from a highish value initially to a lower one afterwards. 12.95 sounds too low but I've never actually measured it under heavy load.