- 2003 X 2.5L SPORT AWD -

So the Jag has been acting a little weird lately. About 2 weeks ago my battery light turn on. (I will say this; I do have a single 10 inch sub in the trunk just because I know that pulls power). Eventually, the battery light turned off. It came back once again last week but has been off since then. Also, one day I turned the car on, the gauges stayed off not moving even while I was already driving.

Im thinking I have a bad alternator or need a new battery....suggestions?

 

It may be a battery issue, but what you are describing with the instrument cluster going dead is sounding more like a bad CAN bus or a possible issue inside of the ECU leading to other indications.

 

Wow, can you elaborate on the "CAN" or the "ECU, leading to other indications"?

 

Prodriver, the CAN bus is the data bus that transfers information all throughout the car. It runs from one computer to the next and to the next. So, if you have a break in this wiring, information can not make it from one computer (say the ECU) to the instrument cluster (another computer). Therefore the instrument cluster is not getting any information and it is lost. So, it goes to zero. When this happens, it thinks it has good information and lights the applicable things (like the battery light since it thinks the car is at zero volts).

The ECU (Engine Control Unit) is nothing more than a big processor. It looks at a lot of data coming in from the various sensors, figures out where in the rotation the engine is, then figures out when and how much fuel/spark to give to the engine. The ECU also has to send out some information to items like the tranny (so its computer knows what gear it needs to select by sending it engine load information) and the instrument cluster (oil pressure, RPM, voltage, etc). So, if the ECU has an internal failure and it can still process information, but that information can not make it out to the outgoing data bus, the information doesn't make it very far.

Is this all starting to make sense?

 

I would still have the battery load tested or maybe just replace it if you have had it a number of years. Also check the battery cables. There is a reason the battery light came on, even if intermittently, so don't ignore it. If it came on twice you can almost bet it will happen again, so don't ignore it.There should be a stored code from when the light came on. See if you can get that read if you have a scanner or go to Autozone and have it read. Our cars are very susceptible to weird things happening when the battery isn't right. That would be the simplest, easiest and cheapest way to start.

 

I had a battery in one of my trucks do this...the battery tested normal but it would die shortly while driving it...turned it out it had a ground fault and would loose all the charge once I started driving thereby killing all my dash lights and etc...sounds like I would start with a battery replacement or possible look to make sure all your power and ground lines are without corrosion and clean if necessary.

 

The gauges staying off for a full drive cycle is something known to happen on rare occasion with the X. I and some others on the forum have reported this happening. For me it happened once, shut the ignition off fully and restarted and the gauges came back. It has never happened again.

It may not be related to your battery issue.

 

@ THERMO.. Yea I know what the ECU is, I work in IT.I just didn't know if you were relating to specific issues in other areas of the car that are caused because of the ECU...Secondly, I just never heard of the CAN abbreviation(believe it or not). But your explanation helps of course even more-so since I know what a PC data bus is.
--- One night I turned my car on and the instrument gauges stayed dead, this has not happened since then. It literally happened once.

As for the battery, the light came on once or twice, both times were as I was actually driving and my 800w speaker system blaring..Maybe i need a stronger alternator for the system and the charging?

My guess is my alternator cant power the battery charging and the system therefore the battery loses charge? (But maybe the battery or alternator are just going dead, or I have bad terminals)