Faulty catalyst temperature sensor reading low or failed internally; Sensor signal wire chafed or shorted to earth; Corroded, damaged or contaminated sensor connector or terminals; Heat damage to wiring or connector near the exhaust; Reference or earth supply fault in the sensor circuit; Fault in the engine control unit.

P043C

Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 2.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
3C: FaultThe specific fault in that area

What it means

P043C is the generic code for a low input from the catalyst temperature sensor circuit on Bank 2, Sensor 2, which sits downstream of the second catalyst on that bank. The engine control unit saw the sensor signal voltage fall below the expected range, which suggests a short to earth, a wiring fault or a failed sensor. Sensor numbering and position vary by model and engine, so confirm the location before testing.

Symptoms

Engine management light on
No noticeable change in driving in many cases
Possible catalyst efficiency or other catalyst-related codes stored alongside
Failed emissions test
Possible reduced performance if the control unit enters a protective strategy on some models

Possible causes

Faulty catalyst temperature sensor reading low or failed internallylikely
Sensor signal wire chafed or shorted to earthlikely
Corroded, damaged or contaminated sensor connector or terminalspossible
Heat damage to wiring or connector near the exhaustpossible
Reference or earth supply fault in the sensor circuitpossible
Fault in the engine control unitrare

How to diagnose

Read all stored codes and freeze frame data, noting engine temperature, load and whether other catalyst or exhaust sensor codes are present
Confirm which bank is Bank 2 and where Sensor 2 sits on this engine using the manufacturer's data
Inspect the sensor wiring and connector for chafing, melting, corrosion, moisture and exhaust contact
Check live data for the sensor reading and see if it responds as the exhaust warms up, or stays fixed at a low value
Wiggle-test the harness with the engine running and watch for the reading changing or the fault returning
With the connector unplugged, test the sensor circuit for short to earth, continuity and supply voltage against the wiring diagram
Check the sensor resistance or output against the specification for that model
Clear the code and road test to confirm whether it returns

How to fix

Replace the catalyst temperature sensor if it is out of specification or reads incorrectly
Repair or replace damaged wiring where it is shorted to earth or chafed
Clean or replace corroded connectors and terminals, and secure the harness away from heat and sharp edges
Repair any earth or reference supply fault found in the circuit
Diagnose and replace the control unit only if all wiring and the sensor are proven good

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this fault is usually not harmful by itself. Book it in soon, as the catalyst temperature is no longer being monitored properly and the car may fail an emissions test.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.