I've replaced the themrostat complete with new housing. All is well car has been doing fine. Then after changing the air filter yesterday the car was doing well then my wife told me about the amber engine light coming on...this supposedly means a perfomrance problem. Could there be a connection with me changing out the air filter and this occurring. I know I need to run codes also but just curious.
Thanks,
Bill

 

Year/model of car? My 2000 XJ8 has a cable/plug to the air box lid for the MAF and air temp sensors, if I recall, that must be unplugged to remove/replace the air cleaner. If that is left unplugged or not re-plugged correctly, the CE light will come on and 'Restricted Performance' message will appear on the diagnostic display.

 

Inspect your reinstall of your filter. Also check the intake hose to the TB and the Breather stub and make sure that they are not cracked and leaking air.

 

Quad-it' a 2002 VDP. Now if this is the case can I go unplug it and then plug it back in and everything be good?
Thanks,
Bill

 

Went back and checked under the hood. The tube (hose guess this is the TB hose) was loose and closed it back (looks tight). Now can I disconnect the MAF sensor plug and re-connect it and that clear it since I did not do that from the start? Also I'm hesitant about disconnecting the plug. Are there two connections (one on top and one on the bottom that hold the plug in place? WOuld someone please describe disconnecting the MAF sensor plug, I don't want to force it and sure as heck don't want to break it. Obvioiusly I'm better off old school without all these new sensors, etc and if I can resolve something that should be simple I would be happy without having to take the car to the shop every time it "sneezes".
Thanks in advance for helping this Jag neophite,
Bill

 

No need to do that if your code is gone. Is it gone? This might help http://www.gusglikas.com/AutoRepairPlugReplacement.htm if at any time you wish to pull the plug to check the connections be sure the car and key are turned off.

 

Gus, the amber engine light is still there. I have not removed the MAF sensor. I did disconnect the battery for over an hour with hopes that would reset the computer and the light would go away. So now I am thinking I need to clean the MAF sensor. I'm open for advice. Thank you for the link....good information.
Bill

 

Can you get the OBD codes that will answer your questions.

 

Disconnecting the battery doesn't reset codes, in fact, doesn't reset anything except your window auto functions and the radio mode functions. You can empty all the capacitors in the car by crossing the positive battery cable to ground after disconnecting to the battery, but this does nothing to clear fault codes either.

Disconnecting the battery is not a step that is going to help with analyzing, fixing and clearing P-codes (or C, U codes for that matter). P-codes, onced diagnosed and problems fixed, are deleted using a scan tool. Some (a very few non-primary) P-codes will clear themselves after a complete engine restart(s). An example of a non-primary P-code is a loose gas cap that is retightened. The MAFS connector is another one. Try it. Unplug the MAFS, start the car, note the CEL. Shut off the engine, replug the MAFS, restart the car and the CEL should be extinguished.

 

All- just a note to say thank you for all your assistance with this problem. As suspected it comes down to my not knowing I need to unplug the MAF sensor prior to changing air filters. YOu've all been very helpful and through the process I have learned a lot about the MAF sensor with these cars. Problem has been corrected and the light is out. Scan confirmed what I didn't do.
Thank you,
Bill

 

Good to know that you got it up and running.