P0428

What does P0428 mean?

P-code P0428 means "Catalyst Temperature Sensor Low Input (Bank 1)". 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 below its expected minimum range for the catalyst temperature sensor low input (bank 1). 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

• Low or no reference voltage supplied to the sensor
• Faulty sensor with a weak or intermittent output signal
• High resistance in the signal wire reducing voltage at the module
• Poor ground connection at the sensor or module

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 P0428
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