Diagnostics and testing 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 brand/fuel quality Installation/sensor status Fan with viscous coupling and electromagnetic valve	Fuses and fuses Wiring harness Electrical connector(s) Sensor(s) Engine Control Module (ECM) Transmission Control Module (TCM)

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

4. Use the approved diagnostic system or scan tool to retrieve all diagnostic trouble codes (DTCs) before referring to the Symptom Chart or DTC Index.

Clear all DTCs after troubleshooting.

Table of signs of malfunction

Sign (general)	Sign (specific)	Possible reasons	Operation
No launch	The engine does not turn over	Security system/immobilizer activated ECM relay Battery Launch system Wiring harness Engine seizure	Make sure the security system is disabled. Check the ECM relay operation. For battery information and starting system tests, refer to the appropriate section of the service manual. Check if the engine cranks over manually.
No launch	The engine turns over but does not start	Low fuel level/contamination Ignition system Fuel system Crankshaft Position Sensor (CKP) Wiring harness ECM failure	Check the fuel level and condition. For ignition and fuel system tests, refer to the appropriate section in the service manual. For CKP sensor and wiring harness tests, refer to the guided diagnostic routine on the approved diagnostic system. If ECM malfunction is suspected, refer to the warranty policy and procedures manual.
No launch	The engine turns over and flashes but does not start.	Fuel Evaporative Canister Purge Valve Fuel system Spark plugs Ignition coil fault(s) Wiring harness	For information on checking the purge valve, fuel system, and ignition system, refer to the appropriate section in the service manual.
Difficulty starting	Difficulty starting at cold start	Check the concentration of antifreeze in the cooling system Battery Crankshaft Position Sensor (CKP) Exhaust Gas Recirculation (EGR) valve stuck open Fuel system Fuel Evaporative Canister Purge Valve	For battery information, refer to the appropriate section in the workshop manual. For CKP sensor and wiring harness tests, refer to the guided diagnostic routine on the approved diagnostic system. For EGR system, fuel system, and purge valve tests, refer to the appropriate section in the workshop manual.
Difficulty starting	Difficulty with hot start	Leak in the injector Fuel system Fuel temperature sensor Intake Air Temperature (IAT) sensor Mass Air Flow (MAF) Sensor Fuel Evaporative Canister Purge Valve Ignition system	Injector and fuel system tests are described in the appropriate section of the service manual. For fuel temperature sensor, IAT sensor, MAF sensor, and purge valve tests, refer to the guided diagnostic routines on the approved diagnostic system. Ignition system tests are described in the appropriate section of the service manual.
Difficulty starting	Difficulty starting after hot soak (the car remains stationary for some time after the engine has reached operating temperature)	Leak in the injector Fuel system Fuel temperature sensor IAT sensor MAF sensor Fuel Evaporative Canister Purge Valve Ignition system	Injector and fuel system tests are described in the appropriate section of the service manual. For fuel temperature sensor, IAT sensor, MAF sensor, and purge valve tests, refer to the guided diagnostic routines on the approved diagnostic system. Ignition system tests are described in the appropriate section of the service manual.
Difficulty starting	Engine cranks too fast/slowly	High/low compression Battery Launch system	Check the compression. Battery information and starting system checks are provided in the relevant section of the service station manual.
The 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 the engine ventilation system. Check the operation of the ECM relay. For MAF sensor tests, refer to the guided diagnostic routines on the approved diagnostic system. Information on checking the ignition system, air intake system information, and fuel lines are provided in the appropriate sections of the service manual.
The engine stalls	Engine stalls when engine braking	ECM relay Throttle Position (TP) Sensors	Check the operation of the ECM relay. For TP sensor tests, refer to the guided diagnostic routines on the approved diagnostic system.
The engine stalls	The engine stalls at a steady speed	ECM relay CKP sensor. TP sensors	Check the operation of the ECM relay. For CKP sensor and TP sensor tests, refer to the guided diagnostic routines on the approved diagnostic system.
The engine stalls	Engine stalls when cruise control is on	ECM relay	Check the operation of the ECM relay.
The engine stalls	The engine stalls when maneuvering	ECM relay TP sensors Additional engine loads (PAS, air conditioning, etc.) Gearbox failure CAN malfunction	Check the operation of the ECM relay. For TP sensor tests, refer to the guided diagnostic routines on the approved diagnostic system. For accessory drive and transmission information, refer to the appropriate section in the workshop manual. Check for CAN fault codes.
Poor overall vehicle handling	Engine lag/poor acceleration	Fuel pump Fuel lines Leak in the injector Fuel pressure Air leak TP sensors Throttle body motor Ignition system EGR valve sticking HO2 sensors Gearbox failure Difficulty moving the pedal (floor covering, etc.) Accelerator Pedal Position Sensor (APP)	For information on checking the fuel pump, fuel lines, injectors, and air intake system, refer to the corresponding section in the Service station manual. For TP sensor and throttle motor checks, refer to the directional diagnostic programs in an approved diagnostic system. For information on checking the ignition system and EGR system, refer to the relevant section in the Service station manual. Check for DTC codes for HO2 sensors, refer to the DTC Code Index. For more information about the gearbox, refer to the corresponding section in the service station manual. Check the accelerator pedal movement. For APP sensor checks, refer to the directional diagnostic programs in an approved diagnostic system.
Poor overall vehicle handling	Backfires in the engine.	Fuel pump Fuel lines Air leak MAF sensor HO2 sensors Ignition system Variable Valve Timing (VCT) Hub Seizure APP sensor	For fuel pump, fuel lines, and air intake system information, refer to the appropriate section in the service manual. For MAF sensor tests, refer to the guided diagnostic routines on the approved diagnostic system. For HO2 sensor DTCs, refer to the DTC Index. For ignition system tests, refer to the appropriate section in the service manual. For VCT and APP sensor tests, 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 body motor Ignition system	For fuel pump and fuel lines, refer to the appropriate section in the service manual. For MAF sensor, TP sensor, and throttle motor tests, refer to the guided diagnostic routines on the approved diagnostic system. Ignition system tests are described in the appropriate section of the service manual.
Poor overall vehicle handling	Detonation/knocking in the engine	Knock sensor (KS)/electrical circuit malfunction Fuel pump Fuel lines Fuel quality MAF sensor HO2 sensors Air leak VCT hub jamming BARO sensor malfunction (internal ECM failure)	For KS electrical circuit tests, refer to the guided diagnostic routines on the approved diagnostic system. For fuel pump and fuel lines, refer to the appropriate section in the workshop manual. For MAF sensor tests, refer to the guided diagnostic routine on the approved diagnostic system. For HO2 sensor DTCs, refer to the DTC Index. For air intake system information, refer to the appropriate section in the workshop manual. For VCT system tests, refer to the guided diagnostic routines on the approved diagnostic system. If ECM malfunction is suspected, refer to the Warranty Policy and Procedures manual.
Poor overall vehicle handling	Lack of throttle response	APP sensor failure TP sensors Throttle body motor	For APP sensor, TP sensor, and throttle motor tests, refer to the guided diagnostic routines on the approved diagnostic system.
Poor overall vehicle handling	Cruise control delay or shutdown	Default mode is enabled Cruise control switch(es) TP sensors CAN bus failure	Check the message center for a default message. For information on cruise control switches, refer to the relevant section in the workshop manual. For TP sensor tests, refer to the guided diagnostic routine on the approved diagnostic system. Check for CAN fault codes.
Poor overall vehicle handling	Poor throttle response	APP sensor failure TP sensors ECT sensor MAF sensor Gearbox failure Activating the traction control system Air leak Disconnection/reduction of ventilation system capacity	For APP sensor, TP sensor, ECT sensor, and MAF sensor tests, refer to the guided diagnostic routines on the approved diagnostic system. For transmission information, air intake system, and ventilation system tests, refer to the appropriate section in the workshop manual.
Poor overall vehicle handling	The engine management system has gone to default values, indicator lamp and messages. Refer to the owner's manual.	TP sensors MAF sensor ECT sensor Wiring harness	For TP sensor, MAF sensor, and ECT sensor tests, refer to the guided diagnostic routines on the approved diagnostic system.

(The material was taken from a website: «lrman.ru»)