Hello,
I own a 2006 Jaguar S-type 3.0L. My airbag light has been on for a while now, and a few days ago, I decided to pull some codes.
The two codes are B1318-Battery Low voltage and B2291-OPS Passenger side. Now, the OPS isn't my priority at the moment.
So here's what I've done to diagnose the problem:
At cold start, the battery voltage is at 15.10V. This is normal as stated in the workshop manual. After a few min, it drops to 13.2V, which is not normal. The lowest setting should be 13.6V. So I check the alternator to make sure that it's output is correct or not. Same story, the red lead shows 13.2V as well. Battery light on dash is not illuminated. After shutdown, the battery is at 12.2V. When I left it overnight, the morning reading was 12.0V-which I think is normal. The same cycle repeats. I have not however checked the wires that run from the battery to the alternator. But I highly doubt thats the problem, because if it were then it would not give an output of 15.10V at start-up!
Any advise to fix the problem is greatly appreciated!

 

Battery voltage across the terminals with the ignition in the OFF position is not normal. There should be a minimum of 12.6 volts available for all modules to function correctly.

Have you performed a load test for at least 10 seconds?

Charge the battery for five hours at 2 to 5 amps and retest. If the voltage is still less than 12.6 volts, the battery is failing or weak.

 

The battery is not failing as it was replaced a year ago at this point and it did pass the load test. At least that's what the dude at AutoZone told me when I checked the battery.

 

What is the voltage across the terminals after several hours before the engine is started?

 

Over night 12.2V. Which i believe is still low.

 

Minimum should be 12.6 volts.

Age of the battery is not indicative of its condition.

 

Sid: What is your location? You, unfortunately like many others, have omitted it from your profile. Are you in a cold or hot climate? This can effect the voltage reading taken at the battery terminals...

 

Sounds to me like your alternator is giving up when it gets hot

here’s my thought process. You charge up your battery, which is a good battery, so when you measure your battery voltage after it’s charged, you get a normal voltage you turn the key to start your car and your car starts normally. But you have a big drain on your battery from starting your car and your alternator sense is that so it pumps out full output to recharge your battery and that’s why you measure 15 V. right after starting the car right after starting your car your alternator is cold and your alternator is working fine.

but then, as your car warms up, the heat causes the voltage regulator inside the alternator to quit. So now you’re no longer charging your battery but your battery still has some voltage in it but it’s being dragged down because the car is running using voltage so you’re reading 13.1 V due to the drain from all the electronics as your car runs, but your battery is not being charged.

Overnight due to residual charges being drained further, your battery continues to decrease in voltage and that’s why the next day you see 12.2 V.

I bet that if you could measure the voltage coming out of the alternator without it connected to the rest of your car (which you obviously can’t do because that would require you to disconnect the output from the alternator with the car running), you’ll see there is no output.

So my diagnosis is you have a faulty alternator that fails once it gets warm

 

Im in New Jersey but the problems has been happening since past summer anyways.