P1419

Code

PEUGEOT P — Powertrain

Catalytic converter downstream temperature sensor short circuit to positive or open circuit

Brand: PEUGEOT

Type: P — Powertrain

Views: UK: 1 EN: 3 RU: 2

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Page language: EN

Check Engine MIL illuminated (fault code stored)
Possible emissions test failure (catalyst monitoring incomplete)
No or erratic downstream catalyst temperature reading in live data
Usually no immediate loss of driveability, but may affect emissions-related functions

Retrieve freeze frame and live data for downstream catalyst temperature (Bank 1/2 as applicable)
Visually inspect sensor, connector and wiring for damage, corrosion, heat damage or repairs
Backprobe connector and observe voltage/temperature signal with ignition on and engine cold then warm
Measure continuity between sensor connector and ECU pin (with ignition off)
Check for short to battery positive using multimeter (resistance to +12 V with circuit disconnected)
Check for short to ground and measure sensor resistance if removable

Expected signal type: thermistor/temperature voltage proportional to resistance (sensor usually wired to ECU pull‑up or reference)
Typical live-data voltage range: 0.1–4.5 V depending on sensor and ECU (refer to factory data)
Open circuit symptom: no changing temperature reading / very high open-circuit voltage or no voltage depending on design
Short-to-positive symptom: steady ~ battery voltage (~12 V) or abnormally high reading on backprobe
Sensor resistance: decreases or increases with temperature depending on sensor type (see service manual for exact ohms-versus-temperature)

Connect a scan tool and confirm P1419 is current or historic; view live downstream catalyst temperature data and related parameters
Record conditions when the fault set (engine temp, load, time since start)
Visually inspect harness and connector at sensor for damage, corrosion, bent pins or heat exposure
With ignition off disconnect sensor and inspect pins; check for water ingress or contaminant
Perform continuity check between the sensor connector and ECU connector pin to confirm wiring integrity (no opens)
With wiring disconnected, measure resistance from the sensor circuit to battery + to detect a short to positive (should be infinite/high resistance if no short)
Backprobe the sensor connector with ignition on (engine off) and note voltage at the signal pin; compare to expected reference in service manual
If possible, remove sensor and measure its resistance versus temperature (compare with factory spec) or substitute a known-good sensor
If wiring and sensor check good, inspect/bench-test ECU input or consult wiring diagram to test ECU driver for faults
Repair or replace failed wiring/connector or sensor as indicated, clear codes and perform drive cycle to verify repair
If fault returns after repair, suspect ECU internal fault and follow manufacturer procedures for ECU testing or replacement

Broken or disconnected harness between sensor and ECU
Connector corrosion allowing intermittent/high voltage reading
Wire chafed against chassis or hot component contacting battery feed
Sensor element failed (infinite or very high resistance / internal short)
Previous repair or aftermarket modification that tied the circuit to battery power

⚠️ Status

Downstream catalytic converter temperature sensor circuit shorted to battery positive or open circuit detected by ECU; sensor reading invalid.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 2.0 hours

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