Description

Jaguar XK, XJ, S-Type, X-Type 2008 Diagnostics Manual

If you have ever chased a Check Engine light on a Jaguar XK or XJ with a generic code list, you know the feeling. Twenty minutes wasted because the aftermarket book said “check O2 sensor” and it was the variable Valve timing solenoid instead. That is why this 2008 Diagnostics Manual exists. It is the same binder Jaguar dealers used when these cars were new. 152 pages of OEM logic, not guesswork.

Variable Valve Timing and Air Intake Systems

Chapter 3.1.3 covers the Variable Valve Timing system for normally aspirated engines. If your S-Type or X-Type has a V6, section 3.1.4 walks you through the Variable Air Intake System. These are the first things to check when the engine feels flat. The manual tells you the exact signal values at the actuator, not a vague “test with multimeter.” For V8s, section 3.1.5 explains the Exhaust Gas Recirculation system monitoring. I have seen techs replace EGR Valves on Jaguars only to find the real issue was a stuck pintle position sensor. This book gives you the range/performance failure criteria so you know before you swap parts.

OBD-II Drive Cycle: Get It Right

Section 2.1 describes the Generic OBD-II Drive Cycle for these Jaguars. If you have ever tried to get a monitor to run and it refuses, you know the frustration. The manual lists the exact conditions: coolant temperature range, engine load, vehicle speed. Page 8 gives the full procedure. Follow that, and the Catalyst Efficiency Monitor or Misfire Monitor will run on the first drive. No more “drive for 10 minutes and hope.”

Catalyst and Misfire Monitors: Factory Procedure

The Catalyst Efficiency Monitor (section 6.1) and Misfire Monitor (6.2) are the two most common causes of a failed smog check. Section 6.2.1 explains misfire detection algorithm – how the ECM counts crank acceleration variations. The manual includes drive cycle information for both monitors. If your XJ or XK is throwing a P0300, this is where you start. Do not rely on a generic scanner. The OEM document tells you which cylinder is misfiring and under what conditions.

Fuel System and Evaporative Emissions Monitoring

Section 6.5 covers the Fuel System Monitor, including secondary trim. If your long-term fuel trims are off, the manual explains how the ECM calculates trim and what values are acceptable. Section 6.6 is the Evaporative Emissions System Monitor – the bane of many DIYers. The leak test operation (6.6.1) is detailed: which valves open, how the fuel tank pressure sensor reacts. That sensor circuit is covered in 6.7 with high/low input and range/performance failures. I have seen more than one Jaguar get a new EVAP canister when the real problem was a $25 fuel tank pressure sensor. The specs on page 73 confirm the voltage range. Use them.

Sensor Diagnostics: From Oxygen to Throttle Position

This manual covers every sensor the ECM uses. Section 6.3 goes 15 subsections deep on Heated Oxygen Sensors – upstream and downstream, heater circuit high/low, slow response. Section 6.10 covers Mass Airflow and Manifold Absolute Pressure sensors. Section 6.16 is Throttle Position Sensor. Each one has a monitoring structure and drive cycle information. If you need to verify a signal, the manual gives you the failure criteria, not a generic “should read 0.5V”. For the Jaguar S-Type with a V8, section 6.8 covers the Exhaust Gas Recirculation system monitor. The whole document is organized by monitor, so you can jump directly to the code you have.

Who Needs This Manual?

If you work on a Jaguar XK, XJ, S-Type, or X-Type at home or in a small shop, and you have an OBD-II scanner that can read mode $06 data, this manual tells you how to use that data. The factory drive cycles are the same ones used by the dealership. I have used this manual to diagnose a P0420 on a 2004 XJ that had three other shops stumped. It was a lazy downstream O2 sensor heater circuit, not the catalyst. The manual’s monitoring structure (section 6.3.3) showed the exact resistance threshold. Saved the customer $1200.

Source Authenticity: OEM vs Aftermarket

I do not trust aftermarket diagnostics manuals for European cars. Aftermarket books omit monitor sequences, skip drive cycle prerequisites, and often use wrong pinouts. This is an original Jaguar publication, revision date April 2008, part of the factory service information system. It is not a reprint or a compilation. The document includes ABS monitors from 2004 model year onward. If you want to diagnose a Jaguar without replacing parts that are fine, this is the source. See the Automotive Industry Overview for why OEM documentation matters.

Related manuals for deeper coverage: Jaguar XK 2007 Training Manual covers chassis and body systems. Jaguar XJ XK8 AJ27 Engine Management Diagnostics Manual goes into the earlier AJ27 V8. For the V6 models, Jaguar S-Type XJ V6 On-Board Diagnostics Manual 2005 is a companion to this 2008 book.

Does this manual cover the fuel injection system?

Yes. Section 3.1.1 covers Fuel Injection. The manual explains the sequential injection strategy and includes monitoring data from the Fuel System Monitor (section 6.5). If you need injector flow rates or pulse width specs, those are in the Engine Management section.

What about the electronic throttle control?

Section 3.1.6. It covers Electronic Throttle Control, idle speed control (3.1.7), and vehicle speed control (3.1.8). Also see Throttle Position Sensor monitor (6.16).

Stop wasting time with aftermarket code definitions. Get the Jaguar factory logic. Access the Factory Manual now and put it on your tablet in the shop.