I have an OBDII reading of PO174 on a 2006 S-Type 4.0 with 58,000 miles. What is the probable cause and where should I start?

 

Start with getting either the motor size or the MY correct. Most likely a vacuum leak though.

 

+1 on providing correct MY or engine. The 2006 S-Type was fitted with the 4.2 litre unit.

The code is P0174 and a vacuum leak is the most likely cause. Fuel trims will help confirm this as well.

 

Next, you should do a search on the Jag Forum for code P0174 (it's a zero, not the letter "O"). There are lots of threads on this code. As mentioned above by one of the most esteemed members of this forum, it's most likely a vacuum leak, as it was on my car. Relatively inexpensive to repair, but you MUST start by knowing exactly what MY and engine you have.

 

Agreed NBCat's knowledge is certainly very much appreciated!

 

Yes....it is a 4.2 L Where can I find a diagram of all of the vacuum lines to check. I tried last nite but was unsuccessful in finding a leak. Perhaps I just haven't checked the right one. I heard that some models must be checked with propane and not carb cleaner. Any truth to that??? I cleaned maf sensor and checked all connections that I could find by spraying cleaner but I feel like I might have missed some. Thanks for your help

 

The quickest and least dangerous way to check for a vacuum leak is by performing a smoke test under bright lights so even a very small leak becomes evident.

Most competent repair shops can perform a smoke test and locate vacuum leaks quickly if you do not have access to such equipment.