Hi, Jag lovers. Glad I found this forum!

I recently bought a 2003 S type with only 56k miles on it.

I just spent thousands of dollars upgrading the car. It was running fine for the past couple weeks, but this morning the "restricted performance " warning came on along with the engine light.

I shut the car off and restarted it. The restricted performance warning went away but the engine light stayed on.

I drive to work with the light on, but the car seems like it's running fine.

I know Jags have a complicated computer/electrical system. How worried should I be? The engine light might be just a minor hiccup.

Any ideas? Thanks!

 

Read the OBD codes. Readers start from $5

 

As above you need to read the engine fault codes.
A cheap reader will do this, but it will not read the other jaguar only codes, for example the ABS and parking sensors.

Once you have the code you can look up what to do on the official Jaguar workshop manual that is available via this link:

http://jagrepair.com/images/AutoRepa...M-Workshop.pdf

It should be noted that poor battery condition with lower than best voltage can cause random faults to be generated, the S-type is way more sensittive to this than other makes..
Some of these faults, like the exhaust O2 sensors for example take two 'drives' without the fault for the fault light to auto re-set on the startup for the third 'drive', but only provided the fault has gone.
If the battery is not so good you may get a morning and evening drive with no fault, but the light still on, however the fault will be back for the start up the next morning when the battery is low again so the light will stay on!

Mellow

 

Usually it's 4 warm-ups without the fault for the MIL to go off.

It's 2 (for many codes) for the fault to flag in the first place.

 

yup. Many times I get excited when my intermittent fault disappears only to be heartbroken at some later time reappears because I never fixed it (but thought I did)