Temperature sensor, cabin air (218): Connection

Sensor pin 3 has an internal ACC unit ground connection via pin 31 (K32) and sensor pin 2 receives a 5 V feed from pin 6 (K32) via an integrated 19.6 Kohm resistor in the ACC unit.

Fig 1: Identifying Communication Flow - Cabin Air Temperature Sensor

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Circuit Diagram - Cabin Air Temperature Sensor

Courtesy of SAAB-SCANIA OF AMERICA, INC.

NTC resistor characteristics allow the resistance to decrease as the temperature rises. This means that the voltage fed over the resistor also decreases as the temperature rises.

The voltage level from the A/D sensor is converted and is then available in digital form. The digital voltage level is then converted to a temperature value which is stored in the ACC unit operating memory. Voltage levels near 0 V or 5 V are determined as circuit faults.