P0440

What does P0440 mean?

P-code P0440 means "Catalyst Temperature Sensor High Input (Bank 2)". It is a generic OBD-II diagnostic trouble code (DTC) in the emissions system. The sensor or circuit is reading a voltage or signal value above its expected maximum range for the catalyst temperature sensor high input (bank 2). This warning should be addressed within the next few days to avoid further damage. This code applies to OBD-II compliant electric and hybrid vehicles.

Possible Causes

• Sensor reference voltage (V_Ref) line shorted to a higher voltage
• Faulty sensor outputting a signal above its calibrated range
• Corroded connector causing erratic high-voltage readings
• Control module failure misinterpreting the sensor signal

Recommended Actions

1. 1 Avoid aggressive driving and schedule a diagnostic appointment within the next 1–3 days
2. 2 Scan for all DTCs with an OBD-II scanner — note any related codes stored alongside P0440
3. 3 Check the sensor reference voltage (should be ~5V) and signal output with a multimeter
4. 4 Clean or replace the sensor connector — corrosion is a common cause of out-of-range voltage readings
5. 5 Clear the DTC, road-test the vehicle, and re-scan to confirm whether the fault returns
6. 6 If the fault persists after inspection and clearing, consult an EV-certified technician for component replacement

Related Emissions fault codes