Catalyst Temperature Sensor High (Bank 1, Sensor 1)
P0428 indicates the catalyst temperature sensor circuit on Bank 1 is reading a voltage that is higher than the PCM's expected range. This sensor monitors exhaust temperature after the catalytic converter to ensure proper catalyst operation and emission control.
What You Might Notice
- Check Engine Light illuminated
- Poor engine performance or hesitation
- Decreased fuel economy
- Increased tailpipe emissions
- Engine running in limp mode on some vehicles
Most Common Causes
- 1
Faulty Catalyst Temperature Sensor
The sensor itself may be failing or producing an out-of-range signal due to internal degradation or exposure to excessive heat and contaminants.
- 2
Wiring or Connector Problems
Corroded, loose, or damaged wiring and connectors in the catalyst temperature sensor circuit can cause high voltage readings.
- 3
Exhaust Air/Fuel Mixture Imbalance
A rich or lean fuel mixture can cause excessive catalyst temperatures, triggering a high sensor signal if the actual exhaust is hotter than expected.
- 4
PCM Programming or Module Fault
Outdated PCM software or a faulty powertrain control module may misinterpret the sensor signal or have incorrect threshold settings.
How to Diagnose It
- 1
Check Faulty Catalyst Temperature Sensor — The sensor itself may be failing or producing an out-of-range signal due to internal degradation or exposure to excessive heat and contaminants.
- 2
Check Wiring or Connector Problems — Corroded, loose, or damaged wiring and connectors in the catalyst temperature sensor circuit can cause high voltage readings.
- 3
Check Exhaust Air/Fuel Mixture Imbalance — A rich or lean fuel mixture can cause excessive catalyst temperatures, triggering a high sensor signal if the actual exhaust is hotter than expected.
- 4
Check PCM Programming or Module Fault — Outdated PCM software or a faulty powertrain control module may misinterpret the sensor signal or have incorrect threshold settings.
How to Fix It
- 1
Inspect and Test Catalyst Temperature Sensor
Use a multimeter to check the sensor voltage at idle and during acceleration. Compare readings to manufacturer specifications. If readings are consistently high or erratic, replace the sensor.
- 2
Check Wiring and Connectors
Inspect the sensor wiring harness and connectors for corrosion, damage, or loose connections. Clean corroded connectors with electrical contact cleaner and ensure all connections are tight.
- 3
Diagnose Fuel Mixture Issues
Perform a fuel system pressure test and check for faulty oxygen sensors or fuel injector problems that could cause a rich condition. Address any underlying fuel delivery or ignition issues.
- 4
Update or Replace PCM
Check for available PCM software updates from the manufacturer and apply if available. If the module itself is faulty, programming or module replacement may be necessary.
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