PTC Sensors

PTC Sensor

PTC Sensor:

PTC (Positive Temperature Coefficient) sensors also change resistance based on temperature. In a PTC sensor as the temperature goes up the resistance also goes up. The increase in resistance causes the voltage drop across the sensor to increase and the input voltage signal at the control module increases.

Typical Application of A PTC Type Sensor

- Exhaust Temp Sensor
- Transmission Temp Sensor

Example of PTC Sensor
A M5 Catalytic Convertor uses a PTC type sensor to monitor exhaust temperature.
A 0-12v signal is supplied to the DME indicating catalyst temperature.

Workshop Hints NTC/PTC Sensors

When troubleshooting a faulty input display, the input signal must be verified as "good" BEFORE the control module is replaced.
When checking a NTC Sensor look for these voltages and problems:
0 volts = no supply voltage or shorted to ground.
2v = sensor is indicating a warm condition for system being measured.
4v = sensor is indicating a cold condition for system being measured.
5v = sensor or wiring harness is open.

Remember a PTC type sensor will indicate opposite results on intermediate readings (i.e. 4 volts = warm).