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Home / DTC / P0425 — Catalytic temperature sensor circuit (bank 1)

P0425 — Catalytic temperature sensor circuit (bank 1)

Detailed page for trouble code P0425.

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P0425

LAND ROVER P — Powertrain

Catalytic temperature sensor circuit (bank 1)

Brand: LAND ROVER
Type: P — Powertrain
Views: UK: 5 EN: 5 RU: 13
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Page language: EN

Causes

  • Open, short or high-resistance in the temperature sensor wiring or connector
  • Failed catalytic converter temperature sensor (thermistor or integrated heater)
  • Corroded, loose or contaminated connector pins
  • Blown fuse or failed relay supplying the sensor heater circuit
  • Damage to wiring from heat, abrasion or rodent chewing
  • Internal PCM/ECM driver failure

Symptoms

  • Malfunction Indicator Lamp (MIL / check engine light) illuminated
  • Possible failed emissions test
  • No noticeable driveability change in many cases
  • Reduced fuel economy or occasional limp-home behavior if ECM limits functions
  • Possible diagnostic trouble codes related to catalyst or O2 sensors

What to check

  • Read stored freeze-frame and live data for catalytic temperature sensor(s), heater control and related O2/catalyst codes
  • Visually inspect sensor, connector and wiring at the catalytic converter for heat damage, corrosion or melting
  • Check fuses and relays that supply the sensor heater circuit
  • Backprobe sensor connector and monitor voltages and signal while cold and during warm-up
  • Measure heater circuit resistance and continuity to the ECM, check for shorts to chassis or battery
  • Verify ECM grounds and power supplies for the sensor circuit

Signal parameters

  • Sensor signal: typical 0–5.0 V logic-range thermistor/voltage signal (refer to OEM spec for exact values)
  • Heater supply: switched 12 V feed from PCM/relay; heater control may be PWM-driven
  • Heater resistance: commonly low-ohm range (tens to low hundreds of ohms) — use OEM spec for exact value
  • Expected behavior: sensor voltage should rise as converter temperature increases; heater circuit should show battery voltage on supply pin and a switched ground on control pin when commanded

Diagnostic algorithm

  1. Confirm code and review freeze-frame / related codes (O2, catalyst codes).
  2. Visually inspect the catalytic converter area, sensor connector and wiring for heat damage, corrosion or physical damage.
  3. Check fuses/relays for the heater circuit and verify PCM power/ground circuits.
  4. With connector disconnected, measure heater resistance across the sensor heater pins and compare to OEM spec; note open or short.
  5. Reconnect and backprobe the sensor harness. With key on/engine running, check for battery feed on heater supply and for PWM/ground switching on the control lead when the engine is warming up or when the ECM commands heater.
  6. Monitor the temperature sensor signal voltage while the engine and converter warm up; verify the voltage increases smoothly and is within expected range.
  7. Perform continuity checks from the sensor connector to the ECM to locate opens/shorts; wiggle wiring to check for intermittent faults.
  8. If wiring and connectors test good but signal/heater out of spec, replace the catalytic temperature sensor. Use OEM or equivalent part.
  9. Clear codes and perform a road/drive cycle to verify repair. If code returns, consider catalytic converter damage or ECM fault and proceed to bench-test or replace ECM only after confirming harness/circuit integrity.

Likely causes

  • Sensor element or heater has failed
  • Connector pins corroded or melted near the converter
  • Short to power or ground in the sensor harness
  • Open circuit due to broken wire or poor repair splice
  • Blown fuse or intermittent ECM output for the heater

Fault status

⚠️ Status
Circuit fault detected in catalytic converter temperature sensor (Bank 1).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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