Temperature Sensor - Waveform Notes
Temperature Sensor (CTS) will invariably be a two wire device with a voltage
itself has the ability to alter its resistance with engine temperature change.
The majority of sensors have a Negative Temperature Coefficient (NTC) which
results in the resistance of the component decreasing as the temperature
The resistance change will therefore alter the voltage seen at the
sensor and can be monitored for any discrepancies across its operational
range. As the temperature increases the resistance decreases and the voltage
will also be seen to drop.
The rate of
voltage change is usually linear with no sudden changes to the voltage.
:- The Vauxhall Simtec system has a point at which the voltage alters
dramatically during the warm up period, this is described in the Coolant
Temperature Sensor (Vauxhall) waveform page.
are manufacturer specific and the outputs will vary dramatically although they
may look identical. Any poor connections on this circuit will introduce an
extra resistance in series and will falsify the readings that the ECM sees,
reading the resistance at the ECM's multi-plug will confirm this.