Tuesday, December 17, 2013

Jaguar X-type common vacuum leaks. P0171 and P0174

Every X-type owner, and I mean every single one, would tell you about that super annoying check engine light caused by the codes P0171 and P0174. First of all let me explain that getting both of these codes at the same time means that we have a common problem with both banks. Why? Here is why:
  • P0171 means that the oxygen sensor reads that there is too much air compared to the fuel coming out of the bank 1 tailpipe.
  • P0174 means that the oxygen sensor reads that there is too much air compared to the fuel coming out of the bank 2 tailpipe.
If both codes are flagged, that means that there is a problem on both sides, which is almost always the case. These cars have a lot of problems with vacuum leaks but most are easily repaired. Here is a picture with the most common problems. I recommend changing all that haven't been changed before because these parts are relatively inexpensive and easy to fix.
  1. Engine Breather Hose
  2. Brake Booster Vacuum Hose
  3. Tuning valve seals

If that doesn't fix your problem, then your most likely cause is a bad Mass Air Flow sensor. Check the link below:


  1. I have a 2003 Jaguar X-Type and I am getting P0174 only, where is this tailpipe 2 located ? Is it on the driver's side of the manifold ?

    1. P0174 is for bank 2 and is located towards the front of the car. Is the "easy" bank.

  2. How easy is it to change these parts myself?

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  4. I appreciate your guidelines. It’s nice information for us.Look complex to far introduced agreeable from you!By the way, how can we keep in touch? my blog

  5. I recently replaced 4 oxygen sensors and oil gasket on my car along with the vaccum seals you talked about. I still have P0171 and P0174 codes. I had no codes before replacing all the 4 oxygen sensors. I have a hissing sound near the brake booster vaccum hose could that bea reason or is it a bad MAF ?

    Any help is greatly appreciated
    I have 03' xtype , 133K miles on it runs smooth

  6. Thanks for the great information. I had no clue about replacing the Vaccuumm seal as Im a computer engineer but foudn this information and did it myself. Thanks a lot again.

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  9. My 2002 X-type 2.5. Has PO171,PO174, PO332 and P1643 when I checked the codes it also showed engine control module/transmission module circuit network, also fuel volume regulator circuit open.It is driving in I believe limp mode and in the driver information window says fault in gearbox,cruise unavailable.The brakes take alot of pressure to work I believe because the brake servo isn't working,I don't know if that is because of a vacuum leak but for the servo to not work due to leak I believe there would have to be a real bad vacuum leak and I would hear it.I just recently bought the car and this has all happened since purchase.When I reverse there is a noise as if the brakes are releasing this is after the car is parked suggesting they are not releasing when I release the handbrake this doesn't happen going forwards and needs alot of revs to move so I always back out of my drive and don't use parking brake except in my driveway. I found receipt in the glove box for replacement brake pads and a couple of other parts on the receipt is written jag parts also the only way I can start the car with the key is to clear the codes otherwise the key turns the lock but doesn't start the car. This is my only vehicle and I cannot afford a big bill at a dealership,I have worked on cars all my working life and did an apprenticeship with a Rolls Royce dealership in Perivale, England where I grew up but these totally computer operated cars have me beat I included this to show I have a background of automobile repairs both mechanical and bodywork I retired 24 years ago due to back injury and now live on social security.

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  12. i have a 02 jag xtype 3.0 petrol that is showing only code p1071.the car runs ok but will not rev over 3000.what should icheck