1995 jaguar xjs v12 check engine codes FF 37 and 44?

Those Jaguar XJS V12 check engine codes (assuming they're OBD1 codes, as OBD2 wasn't fully implemented until later) are likely indicating problems within the system, but aren't standardized codes like you'd find in later OBD systems. You'll need a Jaguar-specific diagnostic tool or a knowledgeable mechanic to interpret them accurately. "FF" especially is unusual and may indicate a fault within the diagnostic system itself or a communication error.

Generic Possible Interpretations (Highly Speculative):

* Code 37: Could relate to issues in the air metering system (MAF sensor, airflow problems), or possibly the throttle position sensor. This is a broad guess, given the lack of standard OBD codes in this era.

* Code 44: Could point to problems in the fuel system, such as fuel injectors, fuel pressure regulator, or even a fuel pump issue. Again, highly speculative without the correct diagnostic tool.

What you should do:

1. Consult a Jaguar specialist: Finding a mechanic familiar with older Jaguars is crucial. They'll have the proper diagnostic equipment (likely a scan tool specific to Jaguar's older systems) and expertise to decipher these codes accurately and diagnose the underlying problem.

2. Avoid guessing and replacing parts: Throwing parts at a car without a proper diagnosis is expensive and inefficient.

3. Check your owner's manual (if available): Although unlikely to contain specific OBD code definitions for these older systems, it might give some clues about common problems.

In short, those codes are not universally understood; you need Jaguar-specific diagnostic tools and expertise for accurate interpretation and repair.