I have a 92 xjs v12, less than 31,000 original miles, 2nd owner, and reg maintenance performed. Today the light came on, and before I take it to the shop, are there reasons for this that are more common than others?

Did check on oil level, tranny fluid, coolant, brake fluid, all are ok.

 

RogB,

What code comes up on the trip computer?

Paul

 

FF45

 

RogB,

FF45 is the lambda sensor on Bank B. Just a suggestion, but I would clear the code, run the car and see if it come back. Depending on the temperature and running conditions, it could just have thrown a spurious code, or it might be a genuine fault.

Good luck

Paul

 

Thanks Paul. Is clearing the code something I can do?

 

RogB,

Once the code has displayed, if you then start the car, it should delete the code from the trip computer and the MIL should be extinguished. if it then comes back, it's because the car has re-detected the fault.

Hope that helps

Paul

 

You can also disconnect the battery to clear the codes, but obviously then you have to reset your radio, etc.

There is a purple wire going to nowhere, ending in a red (or black) connector on the passenger side of the center console, behind the little "ears" cover that has the foot vent in it (Taking this cover off is just a matter of removing the 2 screws holding the foot vent in placer then pulling the cover forward)

If you find this wire, then ground it, it clears the codes for you.

I have connected this wire to a switch that is grounded so I can just throw a switch to clear codes. I was fitting other switches so this seemed to be a sensible addition. These little switches fit perfectly in the ashtrays so once the ashtray is closed you can't see them.

I agree with Pauls approach, ie the first time it appears, clear it and see if it comes back. These early attempts at OBD are quite sensitive and can throw false readings. I notice that if my car has been sitting in the garage, unused for a while, the first one or two runs there's a good chance it'll throw a code. If I've been driving the heck out of it and using it for the whole week, it'll never throw a code...... my take is that these cars really like being driven, and don't like sitting in a garage :-)

 

Thanks Sarc, but in event of future trouble codes, wouldn't that prevent the check engine light from coming on?

 

RogB,

No, the MIL comes on if it "sees" a fault and then stays on. If you clear the code and then the fault happens again, the MIL will illuminate again. If the light doesn't come back, it means the fault has "gone". That's why many people suggest clearing a fault after the first illumination and seeing if it comes back.

Hope that helps

Paul

 

I decided to find the CEL reset connector on my 1994 4.0 so I didn't have to disconnect the battery to clear codes. Thought I would share a couple of photos as I couldn't find any to help me identify it. Purple connector, single yellow/green wire. Connect to ground to clear codes. As you will see in the second shot I relocated mine so I didn't have to remove the kick panel in future.

 

There is a TSB about this code, I don't have the number but you can look it up. It is for later cars, but it may help.

 

I'd also suggest you take a look through my thread HERE, which has a lot of helpful advice about your mirror image problem, FF44. Same problem, other side. In brief, replacing the O2 lambda sensors with a nice couple of Bosch ones did the trick. Just got back from nearly a thousand mile road trip and she didn't miss a beat.

 

The error posts were from 2015. Hopefully the OP found their answers. I just resurrected to document photos.

 

Perhaps a mention that you've resurrected to document next time. I imagine few of us bother to check the dates.