Just joined this forum, having acquired a 2002 XJ8 3.2 from auction. Generally seems pretty sound, but is showing the EML, with "Restricted Performance" on the dash display. Tried plugging in a diagnostic reader into the OBD but it didn't seem to connect - works fine on my Honda CRV though. Any thoughts, please?

I have read some other threads which highlight that a weak battery can throw up all sorts of issues - battery was flat when I got the car, and I have had the battery on charge, and it fires the car up with no issue, but I am aware from my experience on my Alfas that battery weaknesses can cause all sorts of issues, so I'll try running a full recovery/recondition charge on it.

Airbag light is also on, but that's a secondary issue for now..........

Finally, when exploring in the boot to check battery I found this ECU or whatever taped to the top of the boot-mounted fusebox. Any ideas what it is? (Edit - some googling makes me think its a phone controller (there is a phone handset in the centre console....)

Mystery ECU

 

Welcome to the forum. If the code reader does not connect,
it could be difficult to diagnose your issues. I would focus on
finding out why it is not connecting first.

 

Thanks - I've just been checking fuses in the fusebox under the back seat which my handbook says controls the diagnostic but they seem to be OK......I might try another diagnostic tool...

 

Hi RGWM,

Welcome to the Jaguar Forums. It's great to have you with us.

Jaguars do not like batteries that are even slightly weak, so as a first measure you may want to replace yours.

Regarding your scan tool, it is common in my experience for some scan tools to not be able to communicate with an X308. In the U.S., auto parts stores will scan your vehicle for free, so if that is true where you live, it would be worth a try. (It's always helpful to others to at least list the region of the world where you live so we can provide the most accurate replies).

I have found that an ELM327 Bluetooth OBDII interface paired with the Torque Pro app on my Android phone will usually communicate with our X308. If you use an iPhone, you would need a WiFi ELM327 and the DashCommand app. Look for an ELM327 on Amazon or ebay. I keep one in every vehicle.

There are many possible causes of Restricted Performance, so you really are going to need to read the diagnostic trouble codes.

To clear most DTCs, you can disconnect the negative battery cable and touch it to the positive cable terminal for a couple of minutes to clear the keep-alive-memory capacitors in the various electronic control units.

Cheers,

Don

 

Thanks. Don't think here in UK most parts store will do scans, but I have a mate who will probably let me use his professional kit. I have MultiEcuscan which is Fiat /.Alfa dedicated software on my laptop, but I don't think that will be any use

I'll try clearing the DTCs as you suggest as a first try. The car isn't insured and taxed for road use yet (it was an impulse buy) so there isn't a great rush

 

Make sure the scan tool operates on ISO 9141 protocol. You should be able to see this in setup.

 

Hi welcome to the forum. I would source a cheap ELM 327 OBD reader, they're a working device for these cars CAN system.
You're correct on battery condition, these need a solid 12.5V to make sure no spurious readings or faults. A classic example of a low V battery are Engine warning lights 'No Trac' 'No ASC' flashing up on cranking.
The phone is obviously outdated GSM network...
The Airbag will need a better OBD reader that does chassis codes, something like icarsoft i930.

 

If the car runs fine but doesn't go beyond 3 rpm then probably knock sensor however pull the codes first without codes it's headache to find what's wrong

 

Aye the codes, loads of things can cause restricted performance. In my case it was the TPS on the LH side of the TB, but turning the cruise control switch by the gearstick off stopped the code appearing until I sorted it.

 

Thanks all. Just acquired via Amazon (delivered within 13 hours of ordering!) a Topdon bluetooth OBD reader and after a little faffing setting up the app on the phone it gave me a P0137 error (as well as what is probably a spurious B0137 error) which seems to be knock sensor - apparently a pretty common issue, and the Airbag light seems to be driver's side pre-tensioner issue, which should be sortable, I hope. Cleared the DTCs but the P0137 keeps returning - no surprise. Had the battery on a reconditioning charge but it doesnt appear to be achieving full charge so that probably wants replacing. About to go away for a week to attend Alfa racing at Brands Hatch and then the AROC National day at Bicester (I'm a big Alfa freak as well as having always had a soft spot for Jaguars) so won't get chance to do anything for the next week or so, but I do have hopes that this car will purr along the roads again - I took milady on a very brief spin down the farm lane that we live at the top of, and she liked the car..........

 

Your official Jaguar CEL codes should be somewhere for your AJ27 engine

But I didn't see them in this

881 Manual-9-5-01.pdf (jagrepair.com) ​​​​​​​

 

P0137 is the A bank downstream O2 sensor, like spark plugs they wear out, a 22mm O2 socket usually gets them out, the uppers can be a PITA though.

 

You can try cleaning the sensor connector for a cheap try , and swapping sensor positions ( at the pipe )

2 of the 4 sensors are used for engine regulation ( ? ) and best bet is swapping a front upsteam ( S1 ) to rear downstream ( S2 ) on same bank

Bank A will be on cars left ( ? ) , see pic page 14 of the 881 pdf Doc

Your British model may only have 2 O2 sensors total ( ? )

Do not lose track of your original sensor connector positions at the connectors ( they may get crossed like on the earlier Jaguar inline 6 engine )

Do not twist sensor pigtail wires , and look for sensor crush washers , anti - seize on the treads only and never on the tip of the sensor

A quick meter test of the sensors heater 2 pins will let you know the sensor is not getting to it's operating temp to function properly ( Physics )

White / Green wire to the return path wire on the car side of the sensor connector ( the pigtail wires colors are unknown )

See page 55 of the PDF below

And there is a " how to " I think I ran across , looking

Replacing the Upstream O2 Sensors - Page 2 - Jaguar Forums - Jaguar Enthusiasts Forum

jagxj2002.pdf (jagrepair.com)