Peugeot 405 Manual

Fuel injection systems - general information
Fuel/exhaust systems - single-point fuel injection models / Fuel injection systems - general information


Note: The fuel injection ECU is of the selflearning type, meaning that as it operates, it also monitors and stores the settings which give optimum engine performance under all operating conditions. When the battery is disconnected, these settings are lost and the ECU reverts to the base settings programmed into its memory at the factory. On restarting, this may lead to the engine running/idling roughly for a short while, until the ECU has relearned the optimum settings. This process is best accomplished by taking the vehicle on a road test (for approximately 15 minutes), covering all engine speeds and loads, concentrating mainly in the 2500 to 3500 rpm region.

Fenix 1B system
1 The Fenix 1B system is an integrated single-point fuel injection/ignition system.

Using inputs from various sensors, the electronic control unit computes the optimum fuel injector pulse duration, and ignition advance setting, to suit the prevailing engine operating conditions.

2 The electronic control unit receives signals from the following sensors.

a) Engine speed/position sensor.

b) Manifold absolute pressure (MAP) sensor.

c) Inlet air temperature sensor.

d) Throttle position sensor.

e) Coolant temperature sensor.

f) Oxygen sensor.

3 The fuel injection unit houses the fuel injector, the fuel pressure regulator, the throttle position switch, and the idle speed control valve. The single fuel injector injects fuel upstream of the throttle valve.

4 Idle speed is controlled by the electronic control unit, via the idle speed control valve.

5 The oxygen sensor allows the electronic control unit to control the air/fuel mixture within very fine limits, to enable the use of a catalytic converter.

6 All the information supplied to the electronic control unit is computed and compared with pre-set values stored in the module memory, to determine the required period of injection.

7 The electronic control unit constantly varies the fuel mixture, engine idle speed, and ignition timing to provide optimum engine efficiency under all operating conditions, and to reduce exhaust gas emissions. The mixture strength is accurately controlled to maintain it within the operating limits of the catalytic converter.

Bosch Monopoint MA3.0 system 8 The Bosch Monopoint MA3.0 engine management (fuel injection/ignition) system incorporates a closed-loop catalytic converter and an evaporative emission control system, and complies with the latest emission control standards. The system operates as follows.

9 The fuel pump, immersed in the fuel tank, pumps fuel from the fuel tank to the fuel injector, via a filter mounted underneath the rear of the vehicle. Fuel supply pressure is controlled by the pressure regulator in the throttle body assembly. The regulator operates by allowing excess fuel to return to the tank.

10 The electrical control system consists of the ECU, along with the following sensors.

a) Throttle potentiometer - informs the ECU of the throttle position, and the rate of throttle opening or closing.

b) Coolant temperature sensor - informs the ECU of engine temperature.

c) Inlet air temperature sensor - informs the ECU of the temperature of the air passing through the throttle body.

d) Lambda sensor - informs the ECU of the oxygen content of the exhaust gases (explained in Part D of this Chapter).

e) Microswitch (built into the idle speed stepper motor) - informs the ECU when the throttle valve is closed (ie when the accelerator pedal is released).

f) Crankshaft sensor - informs the ECU of engine speed and crankshaft position g) Vehicle speed sensor (fitted to the gearbox) - informs the ECU of road speed.

11 All the above information is analysed by the ECU and, based on this, the ECU determines the appropriate ignition and fuelling requirements for the engine. The ECU controls the fuel injector by varying its pulse width - the length of time the injector is held open - to provide a richer or weaker mixture, as appropriate. The mixture is constantly varied by the ECU, to provide the best setting for cranking, starting (with either a hot or cold engine), warm-up, idle, cruising, and acceleration. Refer to Chapter 5 for further information on the ignition system.

12 The ECU also has full control over the engine idle speed, via a stepper motor which is fitted to the throttle body. The motor pushrod rests against a cam on the throttle valve spindle. When the throttle valve is closed, the ECU uses the motor to vary the opening of the throttle valve and so controls the idle speed.

13 The ECU also controls the exhaust and evaporative emission control systems, which are described in Part D of this Chapter.

14 If there is an error in any of the readings obtained from either the coolant temperature sensor, the inlet air temperature sensor or the lambda sensor, the ECU enters its back-up mode. In this event, the ECU ignores the abnormal sensor signal, and assumes a preprogrammed value which will allow the engine to continue running (albeit at reduced efficiency). If the ECU enters this back-up mode, the warning light on the instrument panel will come on, and the relevant fault code will be stored in the ECU memory.

15 If the warning light comes on, the vehicle should be taken to a Peugeot dealer at the earliest opportunity. A complete test of the engine management system can then be carried out, using a special electronic diagnostic test unit which is simply plugged into the systems diagnostic connector.

Magneti Marelli G5
and G6 systems
16 A Magneti Marelli engine management (fuel injection/ignition) system is fitted to 1580 cc XU5 engines.

17 The fuel injection side of the system operates as described in the following paragraphs. Refer to Chapter 5 for information on the ignition side of the system.

18 The fuel pump, immersed in the fuel tank, pumps fuel from the fuel tank to the fuel injector, via a filter. Fuel supply pressure is controlled by the pressure regulator in the throttle body assembly. The regulator operates by allowing excess fuel to return to the tank. To reduce emissions and to improve driveability when the engine is cold, engine coolant is passed through the manifold and around the throttle body assembly.

19 The electrical control system consists of the ECU, along with the following sensors.

a) Manifold absolute pressure (MAP) sensor - informs the ECU of the load on the engine (expressed in terms of inlet manifold vacuum).

b) Crankshaft sensor - informs the ECU of the crankshaft position and engine speed.

c) Throttle potentiometer - informs the ECU of the throttle position, and the rate of throttle opening/closing.

d) Coolant temperature sensor - informs the ECU of the engine temperature.

e) Fuel/air mixture temperature sensor - informs the ECU of the fuel/air mixture charge temperature entering the engine.

f) Lambda (oxygen) sensor - informs the ECU of the oxygen content of the exhaust gases (explained in greater detail in Part D of this Chapter).

20 In addition, the ECU senses battery voltage (adjusting the injector pulse width to suit, and using the stepper motor to increase the idle speed and, therefore, the alternator output if the voltage is too low). Short-circuit protection and diagnostic capabilities are incorporated into the ECU, and it can both receive and transmit information via the engine management circuit diagnostic connector, thus permitting engine diagnosis and tuning by special diagnostic equipment.

21 All the above signals are compared by the ECU, using digital techniques, with set values pre-programmed (mapped) into its memory.

Based on this information, the ECU selects the response appropriate to those values and controls the ignition HT coil (see Chapter 5), and the fuel injector (varying its pulse width - the length of time the injector is held open - to provide a richer or weaker mixture, as appropriate). The mixture, idle speed and ignition timing are constantly varied by the ECU, to provide the best settings for cranking, starting (with either a hot or cold engine), warm-up, idle, cruising and acceleration.

22 The ECU regulates the engine idle speed via a stepper motor which is fitted to the throttle body. The motor has a pushrod controlling the opening of an air passage which bypasses the throttle valve. When the throttle valve is closed, the ECU controls the movement of the motor pushrod, which regulates the amount of air which flows through the throttle body passage, and so controls the idle speed. The bypass passage is also used as an additional air supply during cold starting.

23 The ECU also controls the exhaust and evaporative emission control systems, which are described in Part D of this Chapter.

24 If there is an error in any of the readings obtained from any of the engine management circuit sensors, the ECU enters its back-up mode. In this event, the ECU ignores the abnormal sensor signal, and assumes a preprogrammed value which will allow the engine to continue running (albeit at reduced efficiency). On entering this back-up mode, the engine management warning light in the instrument panel will come on, informing the driver of the fault, and the relevant fault code will be stored in the ECU memory.

25 If the warning light comes on, the vehicle should be taken to a Peugeot dealer at the earliest opportunity. A complete test of the engine management system can then be carried out, using a special electronic diagnostic test unit which is simply plugged into the systems diagnostic connector.


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