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
NoteAfter switching off the ignition, the double injection relay remains energised for 10 seconds or for 6 minutes in the event of post-ventilation (first and second relay)
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)
NoteThe air gap value is not adjustable
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: according to vehicle
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 opening of the motorised butterfly
- To determine the injection time
- To determine the ignition advance
Description: remote accelerator pedal sensor
Vehicle concerned: CITROEN C8
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
NoteThe accelerator pedal sensor does not have a contact
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: CITROËN XSARA 2
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
NoteThe accelerator pedal sensor does not have a contact
Electrical special features
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
Electrical special features
Electrical features
- Resistance at 20 °C = 6250 ohms
- Resistance at 80 °C = 600 ohms
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 throttle position (throttle potentiometer)
- The engine temperature (coolant thermistor)
- The temperature of the air drawn into the cylinders (air temperature sensor)
- The speed of the vehicle (vehicle speed sensor)
- 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 ignition advance and the coil charging time
- Adjustment of idling speed: Engine temperature, battery voltage, parking, automatic gearbox and air conditioning
- The amount of fuel injected, proportional to the injector opening time
- The idling speed regulation
- The fuel pump
- The fuel vapour recycling (canister bleed electrovalve)
- The injection cut-off on overspeed and deceleration
- The air conditioning cut-off
- The trip computer (instant consumption)
- The tachometer
- Diagnostic warning lamp
- 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 using a diagnostic tool
- Cruise control switch
- 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 (**)
(*) EOBD: European On Board Diagnosis, diagnosis of anti-pollution equipment
(**) CAN = Controller Area Network
The injection ECU software is updated by downloading (ECU fitted with a flash EPROM)
Allocation of channels of connector
| channel number | matching the tracks |
|---|---|
| A1 | input: accelerator pedal sensor signal 1 |
| A2 | input: accelerator pedal sensor signal 2 |
| A3 | input: refrigerant fluid pressure sensor |
| A4 | (not used) |
| B1 | + 5 volts supply: accelerator pedal sensor |
| B2 | input: brake switch |
| B3 | (not used) |
| B4 | the information is taken from the command sent by the BSI |
| C1 | (not used) |
| C2 | (not used) |
| C3 | AC/OUT output |
| C4 | output: diagnostic warning lamp (earth) |
| D1 | (not used) |
| D2 | output: canister bleed valve control |
| D3 | input: air conditioning demand information (by a temperature of AC-TH) |
| D4 | + 5 volts supply: refrigerant fluid pressure sensor |
| E1 | (not used) |
| E2 | (not used) |
| E3 | input: power steering pressure switch |
| E4 | input: refrigerant fluid pressure sensor |
| channel number | matching the tracks |
|---|---|
| F1 | input: clutch switch |
| F2 | input: fan unit diagnostic |
| F3 | engine immobiliser dialogue line |
| F4 | input: wake up for injection ECU, wake up for ADC |
| G1 | (not used) |
| G2 | input: vehicle speed |
| G3 | (not used) |
| G4 | (not used) |
| H1 | (not used) |
| H2 | line K diagnosis |
| H3 | dialogue line: CAN H network |
| H4 | dialogue line: CAN L network |
| J1 | (not used) |
| J2 | output: engine speed |
| J3 | (not used) |
| J4 | output: fan unit 1 control |
| K1 | earth: camshaft position sensor |
| K2 | (not used) |
| K3 | output: engine coolant temperature alarm |
| K4 | output: fan unit 2 control |
| L1 | (not used) |
| L2 | (not used) |
| L3 | (not used) |
| L4 | earth |
| M1 | input: cruise control switch |
| M2 | output: earth control of the air injection to exhaust pump relay |
| M3 | input: low fuel level |
| M4 | earth |
| channel number | matching the tracks |
|---|---|
| A1 | + 5 volts supply: camshaft position sensor |
| A2 | (not used) |
| A3 | input: exhaust gas recycling valve position sensor |
| A3 | input: exhaust gas recycling valve position signal |
| A4 | (not used) |
| B1 | + 5 volts supply |
| B2 | + 5 volts supply |
| B3 | input: engine speed sensor signal (-) |
| B4 | (not used) |
| C1 | earth: inlet manifold air pressure (-) |
| C2 | input: oxygen sensor signal (-) (upstream of the catalytic converter) |
| C3 | input: oxygen sensor richness information (+) (upstream of the catalytic converter) |
| C4 | input: oxygen sensor signal (+) (upstream of the catalytic converter) |
| D1 | earth: engine coolant temperature sensor |
| D2 | + 5 volts supply: throttle position sensor |
| D3 | input: camshaft sensor signal |
| D4 | (not used) |
| E1 | earth: inlet air pressure sensor |
| E2 | input: oxygen sensor signal (-) (downstream of the catalytic converter) |
| E3 | input: engine speed sensor signal (+) |
| E4 | output: for the (+) oxygen sensor heating (downstream of the catalytic converter) |
| F1 | earth: camshaft position sensor |
| F2 | (not used) |
| F3 | output: double relay control (engine fusebox) |
| F4 | output: for the (+) oxygen sensor heating (downstream of the catalytic converter) |
| G1 | output: ignition of cylinder no. 4 |
| G2 | output: butterfly motor control (+) |
| G3 | output: butterfly motor control (-) |
| G4 | after ignition + 12 volts (main supply) |
| H1 | output: ignition of cylinder no. 2 |
| H2 | output: ignition of cylinder no. 1 |
| H3 | output: ignition of cylinder no. 3 |
| H4 | earth |
| channel number | matching the tracks |
|---|---|
| A1 | (not used) |
| A2 | (not used) |
| A3 | (not used) |
| A4 | (not used) |
| B1 | input: alternator charge |
| B2 | input: (+) signal for knock sensor |
| B3 | (not used) |
| B4 | (not used) |
| C1 | input: engine coolant temperature information |
| C2 | (not used) |
| C3 | + 5 volts supply: (sensors) |
| C4 | (not used) |
| D1 | input: inlet manifold air pressure (+) |
| D2 | (not used) |
| D3 | (not used) |
| D4 | (not used) |
| E1 | input: air temperature sensor (+) |
| E2 | input: butterfly position sensor no. 2 |
| E3 | input: butterfly position sensor no. 1 |
| E4 | output: exhaust gas recycling valve control |
| F1 | input: signal for knock sensor (-) |
| F2 | (not used) |
| F3 | output: canister bleed valve control |
| F4 | output: solenoid valve controlling the camshaft dephaser |
| G1 | (not used) |
| G2 | output: injector No 4 control (earth) |
| G3 | output: injector No 2 control (earth) |
| G4 | output: relay control integrated in the engine fusebox |
| G4 | output: engine fusebox double injection relay |
| H1 | earth |
| H2 | earth |
| H3 | output: injector No 1 control (earth) |
| H4 | output: injector No 3 control (earth) |