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:

• Delphi AF10135 Mass Air Flow Sensor