Land Rover Discovery: Piston Cooling Oil Jets Solenoid

The piston cooling oil jets solenoid is located on the left side of the cylinder block, below the thermostat housing. The solenoid is located in a port in the cylinder block and sealed with an O-ring seal. A screw secures the solenoid in the cylinder block.

The piston cooling oil jets solenoid controls the oil supply through a drilling in the cylinder block to the piston oil cooling jets. The solenoid is controlled by the ECM and can open and close the oil supply to the piston oil cooling jets depending on engine speed and load.

DIFFERENTIAL PRESSURE SENSOR - DIESEL PARTICULATE FILTER (DPF)

1. Differential pressure sensor
2. Differential pressure sensor - electrical connector
3. High pressure connection
4. Low pressure connection

The DPF differential pressure sensor is located at the rear of the engine. The sensor is located on a bracket which is attached to the Low Pressure (LP) Exhaust Gas Recirculation (EGR) cooler.

The differential pressure sensor is used by the DPF software in the ECM to monitor the condition of the DPF. Two pipe connections on the sensor are connected by pipes to the inlet and outlet ends of the DPF. The pipes allow the sensor to measure the inlet and outlet pressures of the DPF.

As the amount of particulates trapped by the DPF increases, the pressure at the inlet side of the DPF increases in comparison to the DPF outlet. The DPF software uses this comparison, in conduction with other data, to calculate the accumulated amount of trapped particulates.

By measuring the pressure difference between the DPF inlet and outlet air flow and the DPF temperature, the DPF software in the ECM can determine if the DPF is becoming blocked and requires regeneration.

The DPF is recognized as overloaded if the differential pressure under certain operating conditions exceeds the overload limit calculated by the ECM. The DPF software may start regeneration attempts but be unable to complete them. These attempts are counted by the ECM and, if the maximum number of regeneration attempts is reached, a fault entry is recorded in the ECM at the next ignition on cycle.

The DPF software performs the following checks using the DPF differential pressure sensor:

• Plausibility check
• Diesel particulate filter efficiency
• Diesel particulate filter overloaded
• Diesel particulate filter clogged
• Monitoring of the maximum regeneration attempts in the lower load range.

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

1. High Pressure (HP) Exhaust Gas Recirculation (EGR) valve motor
2. Exhaust Gas Recirculation (EGR) outlet to intake manifold
3. Exhaust Gas Recirculation (EGR) tube from exhaust manifold
4. Air inlet from air filter
5. Pierce point for engine breather hose
6. Turbocharger attachment
7. Engine coolant connection
8. Diesel Particulate Filter (DPF) connection
9. Exhaust Gas Recirculation (EGR) cooler
10. Exhaust Gas Recirculation (EGR) tube assembly

There are two main external Exhaust Gas Recirculation (EGR) systems that are used on the engine - High Pressure (HP) EGR and Low Pressure (LP) EGR.

EGR is used to cool the combustion in the cylinders by introducing exhaust gases without oxygen (exhaust gas). This in turn allows the use of smaller fuel injections, improving emissions and fuel economy.

High Pressure (HP) Exhaust Gas Recirculation (EGR)

The HP EGR valve is attached to the intake manifold. Exhaust gases are routed to the EGR valve from the exhaust manifold. The EGR valve is cooled using engine coolant in the passenger compartment heater core circuit; this is to protect the electrical components from over-heating. The HP EGR valve controls the amount of EGR exhaust gas flow depending on the ECM map.

The exhaust gases are passed directly into the intake manifold via a simple EGR pipe. The design of the EGR pipe attachment to the inlet manifold helps mix the exhaust gasses with the main fresh air intake and also insulates the plastic intake manifold from the hot EGR pipe.

Low Pressure (LP) Exhaust Gas Recirculation (EGR)

The LP system takes exhaust gases from the exit of the catalytic converter, and mixes it with the fresh air intake into the turbocharger.

The LP cooler has no bypass mode, cools all exhaust gas passing through it.

There is a simple mesh filter fitted before the gasses reach the outlet of the cooler that prevents larger particles of soot etc. from entering the turbo charger system. The mesh filter is non-serviceable.

The cooled gases are then directed through the LP EGR valve via a butterfly valve. The valve consists of a tube between the fresh air duct and the turbocharger, with the butterfly valve covering the EGR inlet, in the center bottom of the EGR valve. The butterfly valve opens into the fresh air stream, promoting thorough mixing before the gas enters the turbocharger, and also provides 'suction' to drive the LP EGR gas through the system.

HEATED OXYGEN SENSOR (HO2S)

The HO2S is located in a threaded boss in the inlet to the catalytic converter.

The HO2S allows the ECM to measure the oxygen content of the exhaust gases, for closed loop control of the fuel:air mixture and for catalytic converter monitoring.

The HO2S must operate at high temperatures in order to function correctly.

To achieve the high temperatures required, the sensor is fitted with a heater element that is controlled by a PWM signal from the ECM. The heater element is operated after each engine start, once it has been calculated that there is no moisture in the inlet to the catalytic converter (between 0 and 10 minutes delay). The heater element is also operated during low load conditions when the temperature of the exhaust gases is insufficient to maintain the required sensor temperature. The PWM duty cycle is carefully controlled to prevent thermal shock to a cold sensor. A non-functioning heater delays the sensors readiness for closed loop control and increases emissions.

Diagnosis of electrical faults is continually monitored. This is achieved by checking the signal against maximum and minimum threshold, for open and short circuit conditions.

If the HO2S fails:

• The ECM defaults to open loop fueling
• The Carbon Monoxide (CO) and emissions content of the exhaust gases may increase
• The engine will show reduced refinement and performance if the HO2S fails.

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