Diagnostics and checks (Defender 2007+)

Inspection and verification

1. Check the customer complaint.

2. Visually inspect for obvious signs of mechanical or electrical damage.

Visual inspection

Mechanical elements	Electrical equipment
• Hoses and ducts: condition and installation • Condition and installation of the air filter element • Reduction in the capacity of the air intake system • Condition and installation of vacuum hoses • Pipeline to and from turbocharger: condition and installation • Turbocharger: condition and installation • Charge air cooler	• Fuses • Wiring harness(es) • Weak or corroded connectors • Mass Air Flow (MAF) Sensor • Manifold Absolute Pressure and Temperature (MAPT) sensors • Intake Air Temperature (IAT) sensor • IAT sensor 1 is a component of the MAF sensor

3. If an obvious cause for the problem you identified or the customer described is found, resolve it before proceeding with further actions (if possible).

4. Before referring to the symptom chart or diagnostic trouble code (DTC) index, read all DTCs with a validated diagnostic system or scan tool.

• Clear all DTCs after troubleshooting.

Table of signs of malfunction

Sign	Possible reasons	Operation
The car does not start/starts with difficulty	Reduced air flow/blockage of the air intake system Reduced flow rate/filter element clogging	Check the air intake system for blockages or obstructions. Repair if necessary.
Poor dynamic performance	Air intake system malfunction Turbocharger failure Exhaust Gas Recirculation (EGR) Valve Malfunction Low fuel pressure Clogged exhaust system	NOTE: Ensure that the latest version of the EGR throttle inlet valve is installed. Using the manufacturer approved diagnostic system, check and install the latest software version on the ECM. Check if the variable geometry turbocharger actuator lever moves. For more information, refer to: Turbocharger actuator rod (303-04B Fuel Delivery and Controls - Turbocharger - ID4 2.4L Diesel Engine, Removal and Installation). Check the air intake system for blockages or obstructions. Repair as necessary. Check for DTCs indicating a faulty turbocharger, EGR valve, or incorrect fuel pressure. Repair as necessary. Check the exhaust system for signs of damage or obstructions. Repair as necessary.
Increased noise at intake	Air leak after turbocharger Disconnection/damage to intake manifold after air filter Air filter assembly incorrectly assembled/damaged	Check the air intake hoses or ducts for proper fastening. Check the hoses and ducts for damage, cracks, etc. Repair if necessary.

For a complete list of diagnostic trouble codes that may be stored in the vehicle, see Section 100-00. For additional information, refer to: How to Use This Manual (100-00 General information, Description and operating principle).