P0406: Exhaust Gas Recirculation Sensor A Circuit High
What to do
Usually driveable with no symptom beyond the warning light.
What this code means
The EGR position sensor is reporting a voltage above the plausible range. The mirror of the low-circuit fault, and the causes mirror it too: an open ground, a signal wire shorted to a voltage supply, or a sensor that has failed at the top of its travel.
An open sensor ground is the case worth checking early, because it produces a high reading on a sensor that is otherwise healthy and is easy to confirm with a voltmeter at the connector.
Likely causes
Start here
- Faulty EGR position sensor · easy
- Open sensor ground circuit · moderate
- Corroded or loose connector · easy
Less common
- Signal wire shorted to voltage · moderate
- Damaged wiring harness near exhaust heat · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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