OBD-II Code · Emissions
P0405
EGR Sensor A Circuit Low
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$100–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
EGR position sensor voltage low.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Likely causes
- Failed sensorMost common
- Wiring short
Read the full diagnostic procedureP0405 means the EGR position sensor A signal is reading low — below the minimum voltage threshold the ECM expects to see, typically below 0.2V on a 0…
P0405 means the EGR position sensor A signal is reading low — below the minimum voltage threshold the ECM expects to see, typically below 0.2V on a 0-5V sensor circuit.
This is a sensor or wiring code, not a flow code
- the valve might be operating perfectly, but the feedback signal the ECM uses to confirm position has dropped out.
- Diagnostic ladder: with the ignition on and engine off, backprobe the EGR position sensor signal wire and read voltage at rest (valve closed) — spec is typically 0.6-0.9V at the fully-closed pintle position; anything under 0.4V is a fault.
- Wiggle-test the connector and harness while watching the voltage on the scan tool or a meter — a momentary drop to 0V on wiggle is a chafed signal wire or corroded pin.
- With the connector unplugged, verify 5V reference on the supply pin and clean ground on the ground pin; if either is missing, the fault is upstream of the sensor (ECM-side wiring or a damaged 5V ref shared with other sensors — check for MAP, TPS, or APP codes setting simultaneously).
- If reference and ground are present and the sensor connector reads 5V on the signal wire with the sensor unplugged but drops to 0V when reconnected, the sensor itself is shorted internally — replace it.
- Carbon coking can also drive a position sensor low on integrated EGR-valve-with-built-in-sensor designs because the pintle binds and the sensor wiper stays at the closed-rest position regardless of command.
Vehicle-specific patterns2003-2010 GM 3.5/3.9L V6 and 4.8/5.3L V8 trucks with the linear EGR valve (integrated position sensor) throw P0405 from internal sensor failure — the…
- 2003-2010GM 3.5/3.9L V6 and 4.8/5.3L V8 trucks with the linear EGR valve (integrated position sensor) throw P0405 from internal sensor failure — the wiper inside the valve assembly wears out and the signal goes flat-low; the whole valve has to be replaced ($110-$180 OEM).
- 2002-2008Ford Ranger/Mustang 4.0L SOHC throws P0405 from a corroded EGR sensor connector — the four-pin connector picks up moisture and the signal pin pits; clean and dielectric-grease typically clears it.
- 2004-2009Toyota Sienna/Highlander 3.3L 3MZ-FE throws P0405 from a failed EGR gas temperature sensor (confusingly tied into the same circuit on some Toyota platforms) — verify which sensor the FSM calls "A" before replacing.
- 2005-2010Dodge Ram 5.7L Hemi throws P0405 from a chafed harness behind the intake manifold — the wire runs across the back of the manifold and rubs against the firewall over time.
Estimated repair$30 (connector clean) to $200+ (integrated-sensor EGR valve replacement).
Look up another code
P0405 — frequently asked
What does a P0405 code mean?
EGR position sensor voltage low.
What causes a P0405 code?
Common causes: Failed sensor; Wiring short.
What are the symptoms of a P0405 code?
Typical symptoms: Check engine light.
Is it safe to drive with a P0405 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $100-$400.
How do I diagnose a P0405 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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