Intake air temperature sensors DDE 5.1 M67

The intake air temperature sensors are integrated in the air mass meters and measure the temperature of the fresh air drawn in by the engine in both intake channels.

The intake air temperature serves as a measurement variable in the DDE control units for the following functions:

• Calculation of injection start and fuel injection period
  
• Release of pre-injection
  
• Power requirement calculation, engine
  
• Rail pressure control
  
• Charge-air-pressure control
  
• Exhaust gas recirculation
  
• Glowplug control
  

Function

The DDE control units supply the intake air temperature sensor with voltage and earth as follows:

• U_HR, battery voltage
  
• M_HFM1/M_HFM2, earth
  

The intake air temperature sensors return the intake-air temperature to the DDE control units via the signals T_TANS1/T_TANS2.

The signals for the intake-air temperatures are square-wave signals with the following data:

• Amplitude = 12 V
  
• Frequency = 19 Hz
  

The DDE control units use the pulse duty factor of these signals to calculate the intake-air temperature in °C. The pulse duty factor can lie between 10% and 90%.

Troubleshooting

Fault reactions:

• Exhaust gas recirculation is deactivated
  
• Deactivation of turbo pressure control
  
• Volume limitation
  
• Output of a substitute value dependent on engine speed