P0438
Catalyst Temperature Sensor High (Bank 2)
- Severity
- Medium
- Driving
- Drivable — book it in
The catalyst temperature signal on bank 2 is reading high - typically an open circuit or a short to voltage. Before assuming an electrical fault, consider that a converter really can overheat, and that a misfire is the usual reason.
Possible causes
- CommonFailed catalyst temperature sensor
- CommonCorroded connector - these sit in the hottest, dirtiest part of the vehicle
- CommonWiring damaged by exhaust heat
- PossibleSensor seized in the exhaust and damaged during a previous removal
- PossibleLoss of reference voltage or earth
- PossibleGenuinely wrong exhaust temperature
What you might notice
- Check engine light on
- Failed emissions test
- Slight loss of power
- Sulphurous or rotten-egg smell from the exhaust
- Rattling from the converter if its internals have broken up
- Often no symptom the driver notices
What to check, in order
- A genuinely overheating converter glows and can set fire to what is under the car. If there is any smell of burning or heat haze from underneath, stop and read the misfire guidance rather than assuming a sensor fault.
- Compare the reported temperature with ambient on a vehicle that has stood overnight - they should be close.
- Inspect the connector for corrosion and heat damage. These connectors live in the worst environment on the vehicle.
- Check the wiring where it runs along the exhaust.
- Check the reference voltage and earth at the sensor.
- Expect the sensor to be seized in the exhaust boss - penetrating oil and patience beat force.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Auxiliary emission controls
P0400P0401P0402P0403P0404P0405P0406P0407P0408P0409P0410P0411P0412P0413P0414P0415P0416P0417P0418P0419P0420P0421P0422P0423P0424P0425P0426P0427P0428P0429P0430P0431P0432P0433P0434P0435P0436P0437P0438P0439P0440P0441P0442P0443P0444P0445P0446P0447P0448P0449P0450P0451P0452P0453P0454P0455P0456P0457P0458P0459P0460P0461P0462P0463P0464P0465P0466P0467P0468P0469P0470P0471P0472P0473P0474P0475P0476P0477P0478P0479P0480P0481P0482P0483P0484P0485P0486P0487P0488P0489P0490P0491P0492P0493P0494P0495P0496P0497P0498P0499