Diagnostics and testing 4.4L (Discovery 3)

Inspection and verification

WARNING: Be sure to wear eye protection when working with or in the immediate vicinity of any fuel-related elements. Failure to follow these instructions may result in personal injury.

CAUTION: This procedure involves handling fuel. Always be prepared for possible fuel splashing and follow safe fuel handling practices. Failure to follow this instruction may result in personal injury.

CAUTION: If swallowed, DO NOT induce vomiting. Seek immediate medical attention. Failure to follow this instruction may result in injury.

WARNING: If fuel gets into your eyes, rinse with cold water or an eye wash solution and seek medical attention. Failure to follow this instruction may result in injury.

CAUTION: Wash hands thoroughly after handling as prolonged contact may cause irritation. If irritation occurs, seek medical attention. Failure to follow this instruction may result in injury.

CAUTION: Before disconnecting any fuel system component, be sure to remove all dust and dirt from around the components to prevent dirt from entering the fuel system. Failure to follow this instruction may result in damage to the vehicle.

CAUTION: Therefore, absolute cleanliness is required when working with these components. Open holes or lines must always be plugged using appropriate plugs. Failure to follow this instruction may result in damage to the vehicle.

1. Ensure that the customer's complaint is justified.



2. Visually inspect for obvious mechanical and electrical problems.

Mechanical factors	Electrical factors
Fuel level Fuel contamination/fuel brand/fuel quality Fuel filter Fuel leaks Damaged fuel lines Damaged fittings Fuel tank filler cap Fuel tank filler pipe Roll Over Protection Valves (ROV)	Charging and battery status Fuse(s) Inertia Fuel Switch (IFS) Loose or corroded electrical connectors Wiring harnesses Fuel pump relay Fuel pump module Engine Control Module (ECM)

3. If an obvious cause for the problem you identified or the customer described is found, resolve it before moving on to further action. (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 of malfunction	Possible reasons	Action
The engine turns over but does not start	Inertia Fuel Switch (IFS) Low fuel level/contamination Disconnection/reduction of engine ventilation system flow capacity Ignition system Fuel leak Fuel filter clogged Fuel pump module malfunction Crankshaft Position Sensor (CKP) ECM failure	Check if the inertia switch is activated. Check the fuel level/condition. Check the engine ventilation system. Check for DTC codes related to the ignition system Check the fuel system for leaks/ damage. Check the fuel filter for blockage/ reduced throughput. Check the operation of the fuel pump module. Check the TFR sensor. Refer to the corresponding section in the service station manual. If you have any doubts about the functionality of the module, please refer to the manual on warranty service policies and procedures.
The engine turns over and flashes but does not start.	Fuel Evaporative Canister Purge Valve Low fuel pressure Fuel leak Fuel filter clogged Fuel pump module malfunction Spark plugs Short circuit to ground in high voltage electrical circuit (breakdown). Check rubber boots for cracks/damage Ignition coil failure Wiring harness	Check the evaporative emission purge valve. Check the fuel system pressure. Check the fuel system for leaks/damage. Check the fuel filter for blockages/restrictions. Check the fuel pump module operation. Check the spark plugs and coils. Refer to the appropriate section in the service manual.
Difficulty starting after hot soak (the car is kept after the engine has reached operating temperature)	Leak in the injector Fuel temperature sensor Intake Air Temperature (IAT) sensor Mass Air Flow (MAF) Sensor Fuel Evaporative Canister Purge Valve Fuel pump module malfunction Ignition system	Check the injectors. Check the fuel temperature, IAT, and MAF sensor circuits. Check the EVAP purge valve. Check the fuel pump module operation. Check the spark plug and coil circuits. Refer to the appropriate section in the service manual.
Engine stalls shortly after starting	Disconnection/reduction of ventilation system capacity ECM relay Wiring harness MAF sensor Ignition system Clogged air filter Air leak Fuel lines Fuel Rail Pressure (FRP) Sensor	Check the engine ventilation system. Check the ECM relay and electrical circuits. Check the MAF sensor circuits. Check the spark plug and ignition coil circuits. Check for a clogged air cleaner. Check the air intake system for leaks. Check the fuel lines for leaks/damage. Check the FRP sensor electrical circuits. Refer to the appropriate section in the service manual.
Engine lag/poor acceleration	Difficulty moving the pedal (floor covering, etc.) Exhaust Gas Recirculation (EGR) valve stuck open Ignition system Air leak Heated Oxygen Sensors (HO2S) Fuel pressure Fuel filter clogged Fuel lines Fuel pump module malfunction Leak in the injector Throttle Position (TP) Sensors Throttle body motor Accelerator Pedal Position Sensor (APP) Gearbox failure	Check the accelerator pedal travel. Check the spark plug and ignition coil circuits. Check the air intake system for leaks. Check the HO2 sensor circuits. Check the fuel system pressure. Check the fuel filter for blockages/restrictions. Check the fuel system for leaks/damage.
Backfires in the engine.	Ignition system Air leak Fuel lines Fuel pump module malfunction MAF sensor HO2 sensors APP sensor	Check spark plug and coil circuits. Check air intake system for leaks. Check fuel system for leaks/damage. Check fuel pump module operation. Check MAF, HO2, and APP sensor circuits. Refer to the appropriate section in the service manual.
Engine jerks	Fuel lines Fuel pump module malfunction MAF sensor Wiring harness TP sensors Throttle body motor Ignition system ECM failure	Check the fuel system for leaks/damage. Check the fuel pump module operation. Check the MAF sensor, TP sensor, and throttle motor circuits. Check the ignition coil circuits. Refer to the appropriate section in the service manual. If in doubt about the module, refer to the warranty policy and procedures manual.
Detonation/knocking in the engine	Fuel quality Fuel lines Fuel pump module malfunction Air leak FRP sensor Knock sensor (KS)/electrical circuit malfunction MAF sensor HO2 sensors BARO sensor malfunction (internal ECM failure)	Check fuel for contamination, fuel grade and quality. Check fuel system for leaks/damage. Check fuel pump module operation. Check air intake system for leaks. Check FRP, KS, MAF and HO2 sensor circuits. Refer to the appropriate section in the service manual. If in doubt about the module, refer to the warranty policy and procedures manual.

DTC Index

NOTE: Generic scan tools cannot read the codes listed or can only read 5-digit codes. Match the 5 digits from the scan tool with the first 5 digits of the listed 7-digit code to identify the fault. (the last 2 digits provide additional information readable by a manufacturer approved diagnostic system).

NOTE: For a complete listing of ECM DTCs, refer to Section 303-14, Electronic Engine Control System, in the service manual.

DTC	Description	Possible reasons	Action
P017100	Too much leanness in the system (cylinder bank 1)	Leak in the air intake system between the MAF sensor and the cylinder head MAF sensor malfunction (low air intake flow) Low fuel pressure Reduced fuel filter/fuel system flow capacity Fuel pump module malfunction Reducing fuel injector flow Leak in the exhaust system (before the catalytic converter) Fuel vapor recovery system malfunction	Check the air intake system for leaks. Check the circuits and the MAF sensor. Check the fuel system pressure. Check the fuel filter for blockage/ reduced throughput. Check the fuel system for leaks/ damage. Check the operation of the fuel pump module. Check the injectors. Check the exhaust system for leaks, etc. Refer to the corresponding section in the service station manual. Check for DTC codes for the fuel vapor capture system
P017200	Too much enrichment in the system (cylinder bank 1)	Reducing the air filter capacity High fuel pressure Leaking fuel injector(s) Oil contamination with fuel (too many cold starts without allowing the vehicle to reach a high enough temperature for a sufficiently long time) MAF sensor malfunction Fuel vapor recovery system malfunction	Check the air intake system for blockages. Check the fuel system for leaks, check the fuel pressure. Check the injectors. Check for fuel system DTCs. Check oil cleanliness/grade/quality. Refer to the appropriate section in the service manual. Check for MAF sensor and evaporative emission system DTCs.
P017400	Too much leanness in the system (cylinder bank 2)	Leak in the air intake system between the MAF sensor and the cylinder head MAF sensor malfunction (low air intake flow) Reduced fuel filter/fuel system flow capacity Low fuel pressure Reducing fuel injector flow Leak in the exhaust system (before the catalytic converter) Fuel vapor recovery system malfunction	Check the air intake system for leaks, etc. Check the fuel system for reduced throughput, DTC, etc. Check the exhaust system for leaks, etc. Refer to the corresponding section in the service station manual. Check for DTC codes for the fuel vapor capture system.
P017500	Too much enrichment in the system (cylinder bank 2)	Reducing the air filter capacity High fuel pressure Leaking fuel injector(s) Oil contamination with fuel (too many cold starts without allowing the vehicle to reach a high enough temperature for a sufficiently long time) MAF sensor malfunction Fuel vapor recovery system malfunction	Check the air intake system for restriction, etc. Check the fuel system for leaks, DTCs, etc. Check the oil condition. Refer to the appropriate section in the service manual. Check for DTCs for the MAF sensor and the evaporative emission system.
P030000	Random misfire registered	Malfunctions in the low voltage electrical circuit from the ECM to the ignition coil (also registered DTC codes of misfires in cylinders) Ignition coil failure Malfunction/ contamination/ incorrect spark plug gap Fuel supply pressure (low/high) Fuel injector electrical circuit fault(s) (injector DTC codes are also logged) Reduced flow/leak in fuel injectors Fuel injectors are constantly open Fuel contamination Low compression in the engine cylinder Adjusting valve clearances Worn camshaft/broken valve springs	Check for DTC codes related to the ignition coil. Check the condition and interelectrode gaps of the spark plugs. Check the fuel system pressure. Check for DTC codes associated with the injectors. Check the fuel for contamination, as well as the brand and quality of the fuel. Check the compression in the engine cylinders, check valve clearances, check the condition of the camshaft and valve springs. Refer to the corresponding section in the service station manual.
P046129	Fuel Level Sensor A Circuit Range/Performance Problem	Fuel Level Sensor Circuits: Intermittent Short or High Resistance Fuel level sensor malfunction	Check fuel sensor circuit according to electrical manual. Repair/replace as necessary.
P04612F	Fuel Level Sensor A Circuit Range/Performance Problem	Fuel Level Sensor Circuits: Intermittent Short or High Resistance Fuel level sensor malfunction	Check fuel sensor circuit according to electrical manual. Repair/replace as necessary.
P046200	Fuel Level Sensor Circuit A Low Input Voltage	Fuel Level Sensor Circuits: Intermittent Short to Ground or High Resistance Fuel level sensor malfunction	Check fuel sensor circuit according to electrical manual. Repair/replace as necessary.
P046300	Fuel Level Sensor A Circuit High Input Voltage	Fuel level sensor electrical circuits - intermittent short circuit to battery + Fuel level sensor malfunction	Check fuel sensor circuit according to electrical manual. Repair/replace as necessary.
P062800	Low Voltage in Fuel Pump A Control Circuit	Fuel Pump Control Circuit Short to Ground Fuel Pump Control Circuit High Resistance Fuel pump relay fault	Refer to the electrical manual and check the fuel pump circuits. Activate the relay and listen for a "click". Repair/replace as necessary. Clear DTCs and check for proper operation.
P062900	Fuel Pump A Control Circuit High Voltage	Fuel pump control circuit: short circuit to battery + Fuel pump relay fault	Refer to the electrical manual and check the fuel pump circuits. Activate the relay and listen for a "click". Repair/replace as necessary. Clear DTCs and check for proper operation.
P131500	Persistent misfire	Malfunction in the low voltage circuit from the ECM to the ignition coil (also a cylinder misfire DTC is registered) Ignition coil failure Malfunction/ contamination/ incorrect spark plug gap Low fuel pressure Fuel injector electrical circuit fault(s) (injector DTC codes are also logged) Fuel contamination Low compression in the engine cylinder	Check for DTC codes related to the ignition coil. Check the condition and interelectrode gaps of the spark plugs. Check the fuel system pressure. Check for DTC codes associated with the injectors. Check the fuel for contamination, as well as the brand and quality of the fuel. Check the compression in the cylinders. Refer to the corresponding section in the service station manual.