P0435
Catalyst Temperature Sensor Circuit Malfunction (Bank 2, Sensor 1)P0435 is a generic OBD-II powertrain diagnostic trouble code: Catalyst Temperature Sensor Circuit Malfunction (Bank 2, Sensor 1). It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0435 means
P0435 — Catalyst Temperature Sensor Circuit (Bank 2, Sensor 1) — is a generic circuit fault code indicating that the PCM has detected a problem with the signal from the catalyst temperature sensor on Bank 2. This sensor is a dedicated temperature-measuring device — typically a thermocouple or NTC thermistor — physically mounted on or immediately downstream of the catalytic converter to give the PCM a direct temperature reading. P0435 is the Bank 2 mirror of P0420's temperature sensor family, and specifically the Bank 2 counterpart of P0420 circuit codes; its closest Bank 1 counterpart is P0425.
Important note: on some platforms, particularly older gasoline vehicles without dedicated cat temperature sensors, the OBD-II specification maps "catalyst temperature sensor" codes to the oxygen sensor used to infer catalyst temperature. In these cases P0435 may indicate a Bank 2 upstream O2 sensor circuit fault. The distinction matters for diagnosis — always confirm whether the vehicle has a discrete temperature sensor or uses O2 sensors for catalyst temperature inference before replacing parts.
P0435 is the entry-level circuit code. If the PCM can further classify the fault as electrically low or high, it will additionally store P0437 (voltage low) or P0438 (voltage high). P0435 alone means the signal is absent, erratic, or otherwise outside the plausible electrical range without a definitive high/low classification.
Common causes
Most-frequently reported root causes when P0435 is logged.
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1
Failed catalyst temperature sensor on Bank 2 — internal open circuit or short.
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2
Corroded, damaged, or disconnected wiring connector at the Bank 2 cat temperature sensor.
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3
Chafed or heat-damaged wiring harness routed near the exhaust system.
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4
Open circuit in the sensor signal wire, reference voltage wire, or ground wire between the sensor and PCM.
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5
Short circuit in the sensor wiring (signal to ground or signal to power).
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6
PCM input circuit fault or software calibration error for this sensor channel.
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7
Exhaust leak near the sensor affecting both the reading and the sensor element longevity.
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8
On platforms using O2 sensor for temperature inference: Bank 2 upstream O2 sensor circuit fault.
Symptoms drivers notice
How to diagnose P0435
A typical diagnostic flow when this code is present.
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1
Connect a scan tool and observe the Catalyst Temperature B2S1 live data PID — absent, stuck, or implausible values confirm the circuit fault.
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2
Visually inspect the sensor and connector at the Bank 2 catalyst location for physical damage, heat degradation, corrosion, or loose pins.
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3
With KOEO, measure supply voltage (reference) and ground at the sensor connector; compare to OEM specification.
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4
Measure sensor resistance at ambient temperature with a multimeter — compare to specification (varies by type: NTC thermistors typically 100–2000 Ω at 20 °C; open circuit = infinite; short = near zero).
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5
Inspect the wiring harness from the sensor back to the PCM for chafing against exhaust components, burns, or cuts; use a multimeter to check continuity and insulation resistance.
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6
With engine warm, compare the sensor PID against an infrared thermometer reading at the converter housing — if the housing is hot but the sensor reads cold or zero, the sensor or circuit is faulty.
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7
If wiring and sensor check out, check for TSBs related to PCM software updates for this sensor rationality on the platform.
Related powertrain codes
- P0400 — Exhaust Gas Recirculation Flow Malfunction
- P0401 — Exhaust Gas Recirculation Flow Insufficient Detected
- P0402 — Exhaust Gas Recirculation Flow Excessive Detected
- P0403 — Exhaust Gas Recirculation Circuit Malfunction
- P0404 — Exhaust Gas Recirculation Circuit Range/Performance
- P0405 — Exhaust Gas Recirculation Sensor A Circuit Low
Frequently asked questions
Does every vehicle have a dedicated catalyst temperature sensor?
No. Many gasoline vehicles infer catalyst temperature from the O2 sensor signals rather than using a separate temperature sensor. Discrete catalyst temperature sensors (thermocouples or NTC thermistors) are most common on diesel platforms (for DPF regen management), hybrid vehicles with heated catalysts, and some high-performance or PZEV-rated gasoline engines. If your vehicle lacks a physical sensor, P0435 may refer to the Bank 2 upstream O2 sensor circuit.
What is the difference between P0435 and P0437/P0438?
P0435 is the generic circuit fault — the signal is outside normal electrical bounds but the PCM cannot classify whether it is high or low. P0437 means the signal voltage is below the normal operating range (suggesting an open circuit or failed sensor). P0438 means the signal voltage is above the normal range (suggesting a short to voltage). P0435 often appears when the signal is completely absent or intermittent.
Can I drive with P0435?
On a gasoline vehicle without other symptoms, short-distance driving is usually safe, but the fault should be repaired promptly. On a diesel with a DPF, losing the catalyst temperature sensor degrades regen control, which risks progressive soot overloading of the filter — repairs should not be deferred.
Disabling P0435 in software
RaceTune can permanently disable P0435 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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