Code
P1405
DAEWOO
P — Powertrain
EGR TEMP. UNCERTAIN
Views:
UK: 2
EN: 5
RU: 2
AI status
Completed
Completed
100%
Causes
- Faulty EGR temperature sensor (thermistor or sensor element)
- Open, shorted, corroded or damaged wiring / connector to the EGR temp sensor
- Poor sensor ground or power supply fault
- Intermittent connection or water intrusion at connector
- Severe carbon buildup or blockage in the EGR path affecting sensor exposure
- Faulty EGR valve or actuator causing abnormal conditions
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Reduced driveability: rough idle, hesitation or stumble
- Possible increased emissions or failed emissions test
- Check/limited EGR operation (possible poor fuel trim control)
- Occasional or persistent fault codes related to EGR or temperature sensors
What to check
- Read freeze frame and all stored codes; note operating conditions when code set
- Scan live data: monitor EGR temperature sensor value versus coolant and intake temps
- Visually inspect connectors and wiring at EGR temp sensor for corrosion, damage or moisture
- Backprobe sensor connector and check for expected reference voltage/pull-up and ground
- Measure sensor resistance (cold and warm) or voltage vs temperature and compare to spec
- Wiggle harness while monitoring live data to look for intermittent faults
Signal parameters
- Typical thermistor-type behavior: resistance decreases as temperature rises
- Expected sensor voltage: generally within ~0.1–4.9 V range depending on temp and circuit design
- ECM expects a stable, monotonic change in voltage/resistance with temperature; noisy, stuck or out-of-range values trigger the code
- Operating temperature range: ambient up to exhaust/EGR temperatures (sensor-specific)
Diagnostic algorithm
- Use a scan tool to confirm P1405 is current and review freeze frame data to see engine conditions when set.
- Inspect the EGR temp sensor connector and wiring for corrosion, damage, pin push-out or water intrusion; repair or reseat as needed.
- With ignition off, unplug the sensor and visually inspect pins; then measure sensor resistance at ambient and after warming (compare to service spec if available).
- With ignition on (engine off) backprobe the signal and ground circuits. Verify reference voltage/ground continuity to ECM and that signal voltage is within expected range and changes with temperature.
- Warm the engine or apply heat to the sensor (carefully) while watching live data/voltage to confirm sensor response (use appropriate hot-air and avoid flame).
- Perform a wiring continuity and short-to-ground/power check between the sensor and ECM connector; repair any faults found.
- Inspect EGR valve and passages for carbon that may shield the sensor; clean or service EGR system if obstructed.
- If wiring and sensor test good but fault persists, test/replace ECM connector or consider ECM fault after verifying all other components.
- After repairs, clear codes and perform road test and monitor for recurrence.
Likely causes
- Corroded or loose connector at the EGR temp sensor
- Open or short in the sensor signal or ground circuit
- Failed EGR temperature sensor
- Carbon contamination preventing proper sensing
- Intermittent wiring making the sensor reading unstable
Fault status
Status
EGR temperature sensor signal uncertain or out of expected range — intermittent or invalid reading detected.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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