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?

  3. Thank you very much from Russia!!!

  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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