P043B
Catalyst Temperature Sensor Circuit Range/Performance Bank 2 Sensor 2.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 4
- AreaAuxiliary emission controls
- 3B
- FaultThe specific fault in that area
What it means
P043B is the generic code for a range or performance problem with the catalyst temperature sensor on bank 2, sensor 2, which monitors the temperature at the outlet of the bank 2 catalytic converter. The control unit has seen a signal that does not match the temperature it expects, for example a reading that is implausible, stuck, or fails to change as the exhaust warms up or cools down. Not every vehicle has catalyst temperature sensors, and sensor numbering and location depend on the model and engine.
Symptoms
- Engine management light on
- Reduced performance or limp mode on some models
- Poor fuel economy
- Possible additional catalyst or exhaust temperature codes stored
- No noticeable change in driveability in many cases
Possible causes
- Faulty catalyst temperature sensor (drifted, stuck or slow to respond)likely
- Damaged, chafed or corroded sensor wiring or connectorlikely
- Exhaust leak near the sensor affecting the temperature readingpossible
- Overheated or failing catalytic converter giving temperatures that do not match the expected valuespossible
- Engine misfire or rich or lean running causing abnormal exhaust temperaturespossible
- Heat damage to the sensor or harness from a nearby exhaust componentpossible
- Fault in the engine control unitrare
How to diagnose
- Read all stored and pending codes plus freeze frame data, and note any misfire, fuel trim, catalyst efficiency or other temperature sensor codes.
- Confirm which sensor is bank 2, sensor 2 for this engine, using the manufacturer's information.
- Visually inspect the sensor, wiring and connector for heat damage, chafing, water ingress and corrosion.
- Check the exhaust for leaks or damage around the sensor and catalytic converter.
- With a scan tool, compare live catalyst temperature readings with other exhaust temperature data on a warmed-up engine and watch for stuck or implausible values.
- Test the sensor circuit for supply, signal and ground, and check sensor resistance against the manufacturer's specification.
- Check for misfires and fuel trim problems that could overheat the catalyst, and fix them first.
- Assess the catalytic converter condition if temperatures look genuinely abnormal.
How to fix
- Repair or replace damaged wiring or connectors, and clear any corrosion.
- Replace the bank 2 catalyst temperature sensor if it is faulty.
- Repair exhaust leaks affecting the sensor reading.
- Correct the underlying misfire or fuelling fault, then replace the catalytic converter if it has been damaged.
- Check for a manufacturer software update if one is documented for this fault on the specific model.
Can I keep driving?
The car can usually be driven for a short time, but get it checked soon because a real catalyst overheating problem can cause expensive damage. Avoid hard driving if power is reduced or there is a misfire.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.