Denso Air Conditioner Error Code E06

The E06 error code on a Denso air conditioner indicates a fault detected in the evaporator pipe outlet thermistor, designated CTS3. This sensor is positioned at the outlet of the evaporator coil and continuously monitors refrigerant or pipe temperature at that point in the refrigeration circuit. The controller uses CTS3 data to regulate cooling cycles, prevent coil icing, and protect the system from operating outside safe temperature parameters. When the controller detects a signal from CTS3 that falls outside the expected resistance range, it classifies the fault as either a short circuit (resistance too low) or an open circuit (resistance too high or no signal), and triggers the E06 code to halt or restrict operation.

The most common trigger for E06 is a wiring or connector issue at the CTS3 thermistor. Vibration, moisture intrusion, and repeated thermal cycling can loosen connector pins, corrode terminals, or cause wire insulation to crack and short against the chassis. In many cases, the thermistor itself has not failed but the connection has become intermittent or has separated entirely. This is why the first diagnostic step is to physically reconnect the CTS3 thermistor connector and reset the controller before replacing any components.

If reconnecting and resetting does not clear the fault, the thermistor element itself may have failed. Thermistors degrade over time due to heat stress, moisture, and age, causing their resistance characteristics to drift outside acceptable limits or to fail completely as either an open or short. A resistance check across the CTS3 terminals, compared against the temperature-resistance specification for that sensor, will confirm whether the component requires replacement. Wiring harness continuity should also be verified between the thermistor and the controller board before condemning the sensor.