Yesterday afternoon while driving on the freeway, the check engine light came on and the amber warning light and Restricted Performance message came up. The message went out in about 30 seconds. There was no changed in perforamnce while it was on? The check engine light stayed on. When I got home I read the code, which was P0174. Was this just a fluke, or is the message supposed to go off? Do I just need to disconnect the battery to clear the code, or do I still need to investigate what caused (is causing) the code? Any suggestions?

2003 XJR

Submitted by jcc@majure.com on Wed, 08/31/2011 - 16:14

Thank you George and Harold for the information. I was also able to find the possible causes for the code online - amazing what is out there. Disconnecting the battery did not clear the check engine symbol. I can check a few of the things on the list, but beyond that I'll have to take it to a mechanic. The car has been very reliable up to now so I can't complain (too much!).

JC
2003 XJR

Submitted by hleggett@aol.com on Wed, 08/31/2011 - 09:44

George is right. The list is long.

from http://engine-codes.com ...

P0174 JAGUAR - System Too Lean Bank 2

Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption

Possible causes

- Intake air leaks
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow (MAF) sensor
- Incorrect Positive Crankcase Ventilation (PCV) hose connection

Tech notes

Dirty air filter or faulty air flow sensor are common causes for the P0174 code of the problem.

When is the code detected?

- Fuel injection system does not operate properly.
- The amount of mixture ratio compensation is too small. (The mixture ratio is too lean.)

P0174 JAGUAR Description

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).

Submitted by SE98-32482CJ on Wed, 08/31/2011 - 08:01

JC the possible list for P0174 (which also flags P0171)is rather long and do not have time to type it here. Give me a call on the JCNA tech line and I will read them to you. 888-258-2524 ex #3. Geo.

Submitted by jpbii@yahoo.com on Tue, 08/30/2011 - 23:53

J.C.,

I have a 1999 XJR and get what seem to be erroneous warning lights. They can put me into a panic, but usually reset when I stop the car, turn it off and restart it. I haven't experienced any performance issues when the warning lights appear, but I've never really tested or tried the performance during a display. So, I'm anxious to see what answers you may get about your problem. Sorry I can't offer you any advise. I'm far from any type of mechanic!