Code
P043C
Generic
P — Powertrain
Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 2
Views:
UK: 22
EN: 27
RU: 28
AI status
Completed
Completed
100%
Causes
- Open or shorted sensor wiring or connector (Bank 2 Sensor 2)
- Failed catalyst temperature sensor (thermistor/NTC or heated sensor)
- Corroded, contaminated, or disconnected connector or pin
- Poor ground or supply reference for the sensor circuit
- Damage to exhaust harness near the catalytic converter (heat damage)
- ECM input circuit fault or intermittent ECM ground/power issues
Symptoms
- Check Engine Light illuminated (MIL) with P043C stored
- Failed or disabled catalyst efficiency monitoring for Bank 2
- Possible failed catalytic converter readiness or emissions test failure
- No drivability symptoms in many cases (sensor is post-catalyst)
What to check
- Retrieve freeze frame and live data to confirm conditions when code set
- Visually inspect Bank 2 Sensor 2 connector and wiring for heat damage, corrosion, or disconnection (follow exhaust harness routes)
- Check for other DTCs that indicate upstream/related sensor or heater faults
- Measure sensor connector voltage/ground with connector unplugged/plugged per manufacturer procedure
- Backprobe sensor signal with a good quality DVOM or scope to observe behavior during engine warm-up and after start
- Check continuity and resistance of sensor heater circuit (if equipped) and signal circuit to ECM pins
Signal parameters
- Sensor is typically a temperature sensor (thermistor) that reports as a voltage between ~0.1–4.9 V to the ECM (exact range manufacturer-specific)
- NTC thermistor behavior: resistance decreases as temperature increases (expect rising voltage with rising temp if pull-up reference used)
- A “low” circuit fault is usually a near-zero voltage (example:
- Heater circuit (if present) should show continuity (low ohms) and receive battery voltage or switched power when commanded
Diagnostic algorithm
- Confirm code and note freeze-frame/information from scan tool (engine temp, throttle, rpm, time since start)
- Perform a thorough visual inspection of Bank 2 Sensor 2, its connector, and wiring along the exhaust — look for heat damage, pin corrosion, melted insulation, or broken wires
- Backprobe the sensor signal wire with a DVOM or lab scope while monitoring live data: verify voltage changes as exhaust/catalyst warms during drive or engine conditions that heat the catalyst
- With ignition off, measure resistance of the sensor (if service data available) and compare to specified values at ambient temperature. If heated, measure heater resistance and compare to spec
- Check for proper reference voltage/pull-up and ground at the harness connector. If the reference is missing or shorted, trace and repair wiring to ECM and grounds
- If wiring and connectors are good but signal remains low, replace the catalyst temperature sensor (Bank 2 Sensor 2) and retest
- If replacement sensor does not clear the fault, inspect ECM connector pins and wiring to ECM; consider ECM input circuit testing or replacement only after ruling out wiring and sensor faults
- Clear codes and perform a road/test cycle or a catalyst warm-up procedure to confirm the code does not return
Likely causes
- Damaged/disconnected sensor harness or connector (heat/abrasion)
- Failed catalyst temperature sensor element
- Corroded or pushed-out terminal at connector
- Sensor heater or reference circuit open (if sensor is heated)
Fault status
Status
Catalyst temperature sensor circuit low - Bank 2 Sensor 2
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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