Emissions diagnostics
Emission fault codes describe monitored system performance rather than identifying a failed part. Diagnosis may involve checking purge and vent controls, hoses, fuel tank sealing, oxygen-sensor response, and wiring. A smoke test is useful for many evaporative leaks, but test setup must match the system and manufacturer procedure.
This topic concerns a Jaguar XK in the researched 2014 application (XK X150), including UNKNOWN-V8-5.0L-X150. Equipment, engines and diagnostic procedures can differ even within one model family.
What owners may experience
MIL with P0174 and P0442.
Bank-2 lean and small-EVAP-leak faults.
Fault codes mentioned in the source material include P0174, P0442. A fault code identifies an observed condition; it does not prove which part needs replacement.
How a technician narrows down the cause
The documented investigation included Smoke test; Compare short-term fuel trims. Tests must be adapted to the vehicle and checked against appropriate manufacturer procedures.
Case observations included No obvious leaks; Bank 1 zero; bank 2 +13. Those observations can help narrow a fault but should not be assumed on a different vehicle.
What the documented cases found
Identified causes included Leaking fuel cap. The same symptoms can arise from other failures, so the underlying problem needs to be reproduced and confirmed.
In the researched cases, reported successful actions included Replace fuel cap and reset adaptives/alcohol content. These were case outcomes in the research, not repairs claimed to have been performed by Mich’s Foreign Cars.
When to arrange service
If your Jaguar XK is showing similar warnings, poor performance or intermittent behavior, contact Mich’s Foreign Cars in Hickory, NC. Share the year, engine, exact message, when the symptom occurs and any recorded codes so the diagnostic visit can be planned appropriately.
If you are experiencing this issue, contact Mich’s Foreign Cars in Hickory, NC at 828-324-6012. Provide the model, year, engine, warning text and when the symptoms occur so the service team can discuss an appropriate diagnostic visit.