Sensors and actuators of the Bosch AS3 system (Peugeot 406)

Electronic Control Unit (ECU)

This is the main component of the system, controlling the injection timing, increased idle speed, glow plugs, and the exhaust gas re-burning system.

The ECU receives signals from sensors that monitor coolant temperature, engine speed, fuel injector operation, and engine load. These signals are used by the ECU to control the system.

The ECU unit is located in a plastic box, which is mounted on the right wheel arch.

Removal

Before removing any fuel system component, disconnect the negative battery terminal.



1. Remove the ECU cover (indicated by the arrow).

2. Disconnect the electrical connector by first lifting the locking lever at the top of the connector.

3. Remove the connector from the back, disconnect the front and remove the ECU from the pins.



4. Lift the ECU unit up and remove it from the box.

5. If necessary, remove the ECU box by unscrewing the inner and outer mounting bolts.

Installation

Installation is carried out in the reverse order of removal.

Crankshaft speed sensor

The crankshaft speed sensor is located on the front side of the clutch housing.

This is an inductive pulse generator that creates pulses when the teeth of the flywheel ring gear pass near it.

Coolant temperature sensor

The coolant temperature sensor is a thermistor with a negative temperature coefficient, meaning that as the sensor temperature increases, its resistance decreases.

Atmospheric pressure sensor

The atmospheric pressure sensor is located inside the ECU. This sensor is used to adjust the fuel injection timing depending on the altitude.

Absolute pressure sensor

The sensor is an integral part of the ECU and cannot be removed separately.

Load sensor on the Bosch high pressure fuel pump

Sensor (indicated by the arrow) consists of a potentiometer whose resistance is measured depending on the position of the accelerator pedal. Using this information, the ECU can adjust the fuel injection timing depending on the pedal position and engine load.



The load sensor is mounted on the top of the high pressure fuel pump. Although it can be removed separately, the adjustment of the sensor position after installation requires special Peugeot equipment. Therefore, the replacement of this sensor must be carried out at a Peugeot station.

Injector needle lift sensor

The injector needle lift sensor is an integral part of one of the fuel injectors, which sends a signal to the ECU when the injector opens.

Preheating system control unit

This is an ECU controlled relay that connects the glow plugs of the pre-heating system to the ECU for a specified time when starting a cold engine.

EGR valve

The return of a portion of the exhaust gas to the intake manifold is controlled by the ECU in combination with the EGR solenoid valve and the EGR valve. The vacuum from the vacuum pump is directed to the EGR valve through the solenoid valve according to the engine speed, load and altitude.

Examination

1. If a fault occurs in the system, check that all electrical connectors are connected and not corroded.

2. Check that the air filter element is clean, the compression pressure in the engine cylinders is within normal limits and the engine ventilation hoses are not damaged.

3. If everything looks fine on the outside, but there is a fault in the system, you need to check the fuel system at a Peugeot station.

Removal

1. Trace the wiring from the sensor to the wiring connector and disconnect it from the main harness.

[Information copied from the resource: PeugeotBook.ru]



2. Remove the rubber sealing ring, unscrew the bolts and remove the sensor from the crankcase.

Installation

Installation is carried out in the reverse order of removal.

Control cable and diaphragm

Removal

1. For better access, remove the air intake from the front of the engine.

2. Mark the position of the control cable relative to the lever and disconnect the cable from the high pressure fuel pump.



3. Remove the vacuum hose (A) from the diaphragm assembly (B - bracket mounting bolts).

4. Release the cable from the mounting brackets, unscrew the 2 bracket mounting bolts and remove the bracket from the exhaust manifold.

Installation

1. Installation is carried out in the reverse order of removal.

2. Adjust high idle speed.