Function: injection (TU3JP) Citroen C2 I

Injection double relay (BSM)

(1) double relay

The double relay is incorporated into the engine relay unit

The first relay of the double injection relay supplies the following components

• The injection ECU
• The oxygen sensors

The second relay of the double injection relay supplies the following components

• Booster pump (low pressure)
• Injection ECU (power part)

The airbag units incorporate the function which stops the supply to the low pressure pump (discontinuation of the inertia switch)

The 2 relays are controlled by the injection ECU

The engine fusebox can cut the supply to the second relay in the event of impact

If a pyrotechnic component is deployed, the fuel supply is cut off (cutting of the supply to the second relay)

Starting the engine

• Switch off the ignition
• Switch on the ignition

Engine speed sensor (1313)

Role

The sensor is located opposite the teeth of the flywheel

The role of the injection ECU in terms of the information received

• Checking the engine speed
• To determine the position of the crankshaft
• Calculation of the ignition advance
• To regulate the idle speed

Description

The sensor is of the inductor type

Components of the sensor

• A permanent magnet
• An electric winding

The sensor provides an electrical signal every time a tooth on the flywheel passes by (change in magnetic field)

The 58 teeth are used to work out the engine speed

The 2 missing teeth are used to work out the crankshaft position (no signal)

Electrical special features

Allocation of channels of connector

• Terminal 1: signal
• Terminal 2: earth
• Terminal 3: screening (*)

(*) according to version

Resistance between channels 1 and 2: 425 to 525 Ω

Features of the signals emitted: variable frequency alternating voltage

Location

Location: on the clutch housing

Vehicle speed sensor (1620)

Application: depending on vehicle equipment

Role

The sensor informs the ECU on the vehicle speed

The role of the injection ECU in terms of the information received

• To work out the vehicle speed
• To work out the ratio of the gear engaged
• To improve idling speed when the vehicle is moving
• To optimise acceleration
• To reduce engine hesitation

Description

"Hall effect" sensor

• 5 impulses per metre
• 8 impulses per revolution

Electrical special features

Allocation of channels of connector

• Terminal 1: + 12 volts supply (double injection relay)
• Terminal 2: earth
• Terminal 3: signal

Location

The sensor in located in the gearbox

The camshaft position sensor (1115)

Role

The role of the injection ECU in terms of the information received

• To synchronise fuel injections with respect to the position of the pistons
• To recognise top dead centres
• To determine misfires

Description

"Hall effect" sensor

The camshaft sensor provides a square signal for the injection ECU

Electrical special features

Allocation of channels of connector

• Terminal 1: + 5 volts supply
• Terminal 2: signal
• Terminal 3: earth

The voltage slots are between 0 and 5 volts

Signal emitted

• Presence of metal earth opposite the sensor: 0 Volts
• Absence of metal earth opposite the sensor: 5 Volts

Location

Location: to cylinder head, opposite a target driven by the camshaft

Accelerator pedal sensor (1261)

Role

The sensor is linked to the accelerator pedal by a cable

Role of the sensor

• Records the driver's request (acceleration, decelaration)
• Sends information to injection ECU

The role of the injection ECU in terms of the information received

• To determine the engine's operating mode
• To determine the opening of the motorised butterfly
• To determine the injection time
• To determine the ignition advance
• To determine the injection pressure

Description: remote accelerator pedal sensor

Vehicle concerned: CITROEN C5 - BERLINGO 2 - XSARA PICASSO

The accelerator pedal sensor provides 2 signals (voltage)

The voltage value of one signal is equivalent to half of the other one

Items of information from the connector channels are constantly compared with each other to detect a possible fault

Allocation of channels of connector

• Terminal 1: output signal 1
• Terminal 2: output signal 2
• Terminal 3: 5 Volts
• Terminal 4: earth

Accelerator pedal released

• Voltage between earth and track 1: 0,3 to 0,6 volt
• Voltage between earth and track 2: 0,15 to 0,3 volt

Accelerator pedal pressed fully down

• Voltage between earth and track 1: 3,5 to 4 Volts
• Voltage between earth and track 2: 1,75 to 2 Volts

Location, in the engine compartment

Description: accelerator pedal sensor incorporated in the accelerator pedal

Vehicle concerned: CITROEN C3

The accelerator pedal sensor provides 2 signals (voltage)

The voltage value of one signal is equivalent to half of the other one

Items of information from the connector channels are constantly compared with each other to detect a possible fault

Allocation of channels of connector

• Terminal 1: output signal 1
• Terminal 2: output signal 2
• Terminal 3: 5 Volts
• Terminal 4: earth

Accelerator pedal released

• Voltage between earth and track 1: 0,3 to 0,6 volt
• Voltage between earth and track 2: 0,15 to 0,3 volt

Accelerator pedal pressed fully down

• Voltage between earth and track 1: 3,5 to 4 Volts
• Voltage between earth and track 2: 1,75 to 2 Volts

Engine coolant temperature sensor (1220)

Role

The engine coolant temperature sensor informs the ECU about the engine coolant temperature

The role of the injection ECU in terms of the information received

• To adjust the starting flow
• Adjust the idling speed
• To obtain an accelerated idle speed which decreases as the engine heats up

Description

The sensor consists of a CTN-type resistor (negative temperature coefficient resistance)

The more the temperature increases, the more its resistance value is reduced

Electrical special features

Supply: injection ECU

Allocation of channels of connector

• Terminal 1: + 5 volts supply
• Terminal 2: signal

Electrical features

• Resistance at 20 °C = 6250 ohms
• Resistance at 80 °C = 600 ohms

Air temperature sensor (1310)

Role

The air temperature sensor informs the ECU of the temperature of the air admitted

The role of the injection ECU in terms of the information received

• Calculate the density of the ambient air
• Determine the quantity of fuel to be injected

Description

The sensor consists of a Negative Temperature Coefficient (NTC) resistor

The more the temperature increases, the more its resistance value is reduced

Knock sensor (1120)

Role

The engine knock information, transmitted by the sensor, enables the ECU to correct the ignition advance (reduction)

Knock is a vibratory phenomenon due to an exploding combustion of the air/fuel mixture in one of the 4 cylinders

The sensor transmits voltage peaks to the injection ECU when there is knocking

After engine knocking information, the ECU reduces the ignition timing, and simultaneously enriches the air-fuel mixture

Electrical special features

Supply: injection ECU

Allocation of channels of connector

• Terminal 1: + 5 volts supply
• Terminal 2: signal
• Terminal 3: screening (*)

(*) according to version

Location

Location: cylinder block

Upstream oxygen sensor (1350)

Role

Location: the oxygen sensor is located in the exhaust line, between the engine and the catalytic converter

These hydrocarbons alter the state of the reference air in the sensor and therefore the mixture signal accuracy

The role of the injection ECU in terms of the information received

• To determine the fuel / air mixture (richness)
• Mixture regulation

Description

The oxygen sensor informs almost continuously the ECU about the air-fuel mixture ratio

The "rich" or "lean" mixture information is given by 0 to 1 V voltages

• Lean mixture = 0,1V
• Rich mixture = 0,9V

A heating device placed inside the sensor enables it to rapidly reach its operating temperature (+ 300°C)

Electrical special features

The sensor is equipped with a 4 way caliper connector

Allocation of channels of connector

• Terminal 1: + 12 volts supply (oxygen sensor heater)
• Terminal 2: earth
• Terminal 3: + signal
• Terminal 4: - signal

Power steering pressure switch (7001)

Role

The steering pressure switch allows the engine ECU to increase the engine idling speed when parking

Conditions for increasing the idling speed

• Vehicle speed lower than 4 kph
• Pressure switch activated (power-assisted steering)

Location

On the union between the power assisted steering valve and pump

Injection ECU (1320)

Role

The engine ECU manages the injection using the engine torque information

• The engine ecu calculates the engine torque requirement by means of the accelerator pedal sensor
• The engine torque request takes account of a number of corrections (torque absorbed by the alternator, torque absorbed by the air con compressor etc.)
• The engine torque request is converted into injection timing, injection phasing, butterfly opening, and ignition advance

The ECU controls the ignition and the injection depending on the various parameters received

These parameters are

• The engine speed and the crankshaft position (TDC sensor - camshaft position sensor)
• The inlet air pressure (pressure sensor)
• The position of the accelerator pedal
• The engine temperature (coolant thermistor)
• The temperature of the air drawn into the cylinders (air temperature sensor)
• The engine coolant temperature
• The torque absorbed by the alternator
• The torque absorbed by the air conditioning compressor (calculation)
• The speed of the vehicle (vehicle speed sensor speed information provided by the ESP ECU)
• The oxygen content of exhaust gases (oxygen sensor)
• The pinking (knock sensor)
• The air conditioning demand
• The battery voltage
• The pressure in the power assisted steering circuit
• Automatic gearbox ECU

By making use of the information, the ECU controls

• The opening of the butterfly housing
• The idling speed regulation
• The ignition advance and the coil charging time
• The amount of fuel injected, proportional to the injector opening time
• The fuel vapour recycling (canister bleed electrovalve)
• The injection cut-off on overspeed and deceleration
• The air conditioning cut-off
• The tachometer
• The oxygen sensor heating element (downstream oxygen sensor, upstream oxygen sensor)
• The secondary air pump (air injection into the exhaust function)
• The exhaust gas recirculation valve

The ECU also controls the following functions

• Emergency strategies
• The diagnostic with memorisation of failures
• Cruise control
• Reduction of engine torque during an ESP adjustment
• Engine cooling
• Cooling requirement for the air conditioning (BRAC)
• Speed control
• Transponder
• Dialogue with other ECUs (automatic gearbox, BSI, ABS etc.) via the CAN network (**)

(**) CAN = Controller Area Network

The injection ECU software is updated by downloading (ECU fitted with a flash EPROM)

Allocation of channels of connector