Shown on engine 471.9, code (M5Z) Euro VI engine version |
A4 | Engine management control unit (MCM) |
B606 | Exhaust coolant temperature sensor |
B607 | Intake coolant temperature sensor |
CAN 4 | Drive train CAN |
W07.16-1061-81
General
The coolant temperature which is required for a number of factors, including fan regulation or computation of the actuation begin of fuel injectors, is determined by the engine management (MCM) control unit (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).
In order to determine the actuation begin as well as the actuation period (=injection quantity) of the fuel injectors, the engine management (MCM) control unit (A4) exclusively uses measurements from the coolant outlet temperature sensor (B606).
Function
Both sensors, the intake coolant temperature sensor (B607) and the exhaust coolant temperature sensor (B606), are fitted with a temperature-dependent resistance with a negative temperature coefficient (NTC) - that is an electrical resistance which reduces as the temperature increases.
According to how the temperature of the coolant at the coolant inlet coolant temperature sensor (B607) or exhaust (B606) the applied voltage changes on the engine management (MCM) control unit (A4) the level of which the intake and exhaust coolant temperature is determined.
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.