Catalyst Temperature Sensor High (Bank 1, Sensor 1)
The P0428 code indicates that the catalyst temperature sensor (Bank 1, Sensor 1) is reporting a voltage higher than the expected range. This sensor monitors the temperature of the catalytic converter to ensure it is operating efficiently. A high reading can be caused by a faulty sensor, wiring issues, or an actual overheating catalytic converter due to engine misfires, rich fuel mixture, or restricted exhaust.
01. Most Common Causes
- Faulty catalyst temperature sensor
- Short circuit or damaged wiring/connector
- Overheating catalytic converter due to engine misfire or rich fuel mixture
- Exhaust leak near the sensor
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Possible reduced fuel economy
- Possible engine performance issues (hesitation, rough idle)
- Possible catalytic converter damage if overheating persists
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for additional codes.
Step 2: Visually inspect the catalyst temperature sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's resistance and voltage output with a multimeter and compare to manufacturer specifications.
Step 4: Check for exhaust leaks near the sensor and inspect the catalytic converter for signs of overheating (discoloration, melting).
Step 5: If the sensor and wiring are okay, diagnose potential causes of converter overheating (e.g., misfires, rich fuel trim).
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as the catalytic converter may overheat and become damaged, leading to costly repairs. Have the issue diagnosed promptly.
How much does it cost to fix?▼
The cost to replace a catalyst temperature sensor typically ranges from $50 to $150 for parts and labor. If the catalytic converter is damaged, replacement can cost $500-$2,500 or more.