P043C

Code

Generic P — Powertrain

Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 2

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 27 RU: 28

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Page language: EN

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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