Diagnosis and check 4.4L (Discovery 3)

Inspection and verification

1. Check the validity of the customer's complaint.

2. Visually inspect for obvious mechanical and electrical problems.

Mechanical factors	Electrical Factors
Engine oil level. coolant level Fuel level Fuel contamination / fuel grade / fuel quality Sensor installation/status Viscous fan and solenoid valve	Fuses Wiring harness electrical connector (s) Sensor (And) Engine control module (ECM) transmission control module (TCM)

3. If an obvious cause of a problem you identified or described by the customer is found, correct it before proceeding to the next steps (if possible).

4. Use an approved diagnostic system or scan tool (tester), to retrieve all DTCs before referring to the Symptom Table or DTC Index (DTC).

Clear all DTCs after troubleshooting.

Symptom table

sign (general)	sign (specific)	Possible reasons	Operation
Lack of launch	Engine won't crank	Security system/ immobilizer activated ECM relay Battery Launch system Wiring harness Engine jam	Make sure the security system is disabled. Check the operation of the ECM relay. For information about the battery and a description of the checks on the starting system, see the relevant section of the workshop manual. Check if the engine turns by hand.
Lack of launch	Engine cranks but won't start	Low/contaminated fuel Ignition system Fuel system crankshaft position sensor (CKP) Wiring harness ECM malfunction	Check the level and condition of the fuel. For ignition and fuel system checks, refer to the appropriate section in the workshop manual. Refer to the guided diagnostic routine on the approved diagnostic system for CKP sensor and wiring harness checks. If an ECM malfunction is suspected, refer to the warranty policy and procedures manual.
Lack of launch	Engine cranks and flashes but won't start	EVAP canister purge valve Fuel system Spark plug Malfunction (And) ignition coils Wiring harness	For purge valve, fuel system, and ignition system checks, refer to the appropriate section in the workshop manual.
Difficulty starting	Cold start difficulties	Check the concentration of antifreeze in the cooling system Battery crankshaft position sensor (CKP) Jamming in the open position of the exhaust gas recirculation valve (EGR) Fuel system EVAP canister purge valve	For battery information, refer to the appropriate section in the workshop manual. Refer to the guided diagnostic routine on the approved diagnostic system for CKP sensor and wiring harness checks. For EGR system, fuel system, and purge valve checks, refer to the appropriate section in the workshop manual.
Difficulty starting	Hot Start Difficulties	Nozzle leak Fuel system Fuel temperature sensor Air intake temperature sensor (IAT) Mass air flow sensor (MAF) EVAP canister purge valve Ignition system	Injector and fuel system checks are described in the relevant section of the workshop manual. For fuel temperature sensor, IAT sensor, MAF sensor, and purge valve checks, refer to the guided diagnostic routines in the approved diagnostic system. Ignition system checks are described in the appropriate section of the workshop manual.
Difficulty starting	Difficulty starting after a hot soak (the vehicle remains stationary for a while after the engine has reached operating temperature)	Nozzle leak Fuel system Fuel temperature sensor IAT sensor MAF sensor EVAP canister purge valve Ignition system	Injector and fuel system checks are described in the relevant section of the workshop manual. For fuel temperature sensor, IAT sensor, MAF sensor, and purge valve checks, refer to the guided diagnostic routines in the approved diagnostic system. Ignition system checks are described in the appropriate section of the workshop manual.
Difficulty starting	Engine cranks too fast/slow	High/Low Compression Battery Launch system	Check compression. For information about the battery and a description of the checks on the starting system, see the relevant section of the workshop manual.
Engine stalls	Engine stalls shortly after starting	Disconnection / reduction of ventilation system capacity ECM relay MAF sensor Ignition system Clogged air filter Air leak Fuel lines	Check engine ventilation system. Check the operation of the ECM relay. For MAF sensor checks, refer to the guided diagnostic routines on the approved diagnostic system. For information on checking the ignition system, information about the air intake system and fuel lines, see the relevant sections of the workshop manual.
Engine stalls	Engine stalls when braking	ECM relay Throttle Position Sensors (TR)	Check the operation of the ECM relay. For TP sensor checks, refer to the guided diagnostic routines on the approved diagnostic system.
Engine stalls	Engine stalls at steady speed	ECM relay CKP sensor. TP sensors	Check the operation of the ECM relay. For CKP sensor and TP sensor checks, refer to the guided diagnostic routines on the approved diagnostic system.
Engine stalls	Engine stalls when cruise control is on	ECM relay	Check the operation of the ECM relay.
Engine stalls	Engine stalls when maneuvering	ECM relay TP sensors Additional engine loads (PAS, air conditioning, etc.) Transmission malfunction CAN fault	Check the operation of the ECM relay. For TP sensor checks, refer to the guided diagnostic routines on the approved diagnostic system. For information on the accessory drive and gearbox, refer to the appropriate section in the workshop manual. Check for CAN DTCs.
Poor overall vehicle handling	Engine acceleration lag/poor acceleration	Fuel pump Fuel lines Nozzle leak Fuel pressure Air leak TP sensors Throttle motor Ignition system EGR valve sticking HO2 sensors Transmission malfunction Difficulty moving the pedal (flooring, etc.) Accelerator pedal position sensor (APP)	For information on checking the fuel pump, fuel lines, injectors and air intake system, refer to the appropriate section in the workshop manual. For TP sensor and throttle motor checks, refer to the guided diagnostic routines on the approved diagnostic system. For ignition system and EGR system checks, refer to the appropriate section in the workshop manual. Check for DTCs for HO2 sensors, refer to the DTC Index. For gearbox information, refer to the appropriate section in the workshop manual. Check the movement of the accelerator pedal. For APP sensor checks, refer to the guided diagnostic routines on the approved diagnostic system.
Poor overall vehicle handling	Backfires in the engine.	Fuel pump Fuel lines Air leak MAF sensor HO2 sensors Ignition system Jamming of the hub of the variable valve timing system (VCT) APP sensor	For information about the fuel pump, fuel lines and air intake system, refer to the appropriate section in the workshop manual. For MAF sensor checks, refer to the guided diagnostic routines on the approved diagnostic system. Check for DTCs for HO2 sensors, refer to the DTC Index. Ignition system checks are described in the appropriate section of the workshop manual. For VCT and APP sensor checks, refer to the guided diagnostic routines on the approved diagnostic system.
Poor overall vehicle handling	Engine Jerks	Fuel pump Fuel lines MAF sensor Wiring harness TP sensors Throttle motor Ignition system	For information about the fuel pump and fuel lines, refer to the appropriate section in the workshop manual. For MAF sensor, TP sensor, and throttle motor checks, refer to the guided diagnostic routines in the approved diagnostic system. Ignition system checks are described in the appropriate section of the workshop manual.
Poor overall vehicle handling	Detonation / knocking in the engine	Knock sensor malfunction (KS) / electrical circuit Fuel pump Fuel lines Fuel quality MAF sensor HO2 sensors Air leak Jamming of the hub of the VCT system BARO sensor malfunction (internal ECM malfunction)	For KS electrical circuit checks, refer to the guided diagnostic routines on the approved diagnostic system. For information about the fuel pump and fuel lines, refer to the appropriate section in the workshop manual. For MAF sensor checks, refer to the guided diagnostic program on the approved diagnostic system. Check for DTCs for HO2 sensors, refer to the DTC Index. For information about the air intake system, refer to the appropriate section in the workshop manual. For VCT system checks, refer to the guided diagnostic programs on the approved diagnostic system. If an ECM malfunction is suspected, refer to the warranty policy and procedures manual.
Poor overall vehicle handling	Lack of throttle response	APP sensor malfunction TP sensors Throttle motor	For APP sensor, TP sensor, and throttle motor checks, refer to the guided diagnostic routines in the approved diagnostic system.
Poor overall vehicle handling	Delayed operation or deactivation of cruise control	Default mode enabled Switch (And) cruise control systems TP sensors CAN bus failure	Check the message center for a default message. For cruise control system switches, refer to the appropriate section in the workshop manual. For TP sensor checks, refer to the guided diagnostic program on the approved diagnostic system. Check for CAN DTCs.
Poor overall vehicle handling	Poor throttle response	APP sensor malfunction TP sensors ECT sensor MAF sensor Transmission malfunction Traction control activation Air leak Disconnection / reduction of ventilation system capacity	For APP sensor, TP sensor, ECT sensor, and MAF sensor checks, refer to the guided diagnostic routines on the approved diagnostic system. Information about the gearbox, air intake and ventilation system checks are given in the appropriate section in the manual for service stations.
Poor overall vehicle handling	The engine management system has moved to default values, warning lamp and messages. Please refer to the instruction manual.	TP sensors MAF sensor ECT sensor Wiring harness	For TP sensor, MAF sensor, and ECT sensor checks, refer to the guided diagnostic routines on the approved diagnostic system.