Shown on engine 471.9 |
A4 | Engine management control unit (MCM) |
B606 | Exhaust coolant temperature sensor |
B607 | Intake coolant temperature sensor |
CAN 4 | Drive train CAN |
W07.16-1207-81
General
The coolant temperature, which is required e.g. for fan control or to calculate the start of fuel injector actuation, is determined by the engine management control unit (MCM) (A4).
For fan regulation the engine management (MCM) control unit (A4) uses measurements made by the coolant intake temperature sensor (B607) and the coolant outlet temperature sensor (B606).
To determine the start of actuation as well as the actuation duration (injection quantity) of the cylinder 1 fuel injector (Y608), cylinder 2 fuel injector (Y609), cylinder 3 fuel injector (Y610), cylinder 4 fuel injector (Y611), cylinder 5 fuel injector (Y612), and cylinder 6 fuel injector (Y613), the engine management control unit (MCM) (A4) exclusively uses the measurement values of the exhaust coolant temperature sensor (B606).
Function
The intake coolant temperature sensor (B607) and exhaust coolant temperature sensor (B606) each contain a temperature-dependent resistor with a negative temperature coefficient (NTC), i.e. an electrical resistance that decreases as the temperature increases.
Depending on the temperature of the coolant at the intake coolant temperature sensor (B607) or exhaust coolant temperature sensor (B606), the voltage present at the engine management control unit (MCM) (A4) changes; its level is used to determine the intake or exhaust coolant temperature.
If one of the sensors fails the engine management (MCM) control unit (A4) continues to operate with substitute values.
This allows the engine to be started even under unfavorable conditions and for the vehicle to continue to be driven.
The engine management (MCM) control unit (A4) will limit the specified engine torque to protect the engine from overheating if the coolant temperature reaches an impermissibly high value.