P0406: EGR position sensor signal too high
Exhaust gas recirculation sensor A circuit high
Severity: Monitor
PartsAvatar says P0406 is not immediately critical but affects emissions control and engine performance.
It gets more serious if:
- Inspect soon: Have it inspected soon if the engine surges or stalls intermittently, both listed symptoms.
P0406 in short
P0406 means the EGR position sensor is sending a voltage higher than the computer expects. The usual causes are a faulty EGR valve with its built-in sensor, a signal wire shorted to battery voltage, or carbon build-up. It is usually driveable, but surging or stalling needs a prompt check.
Many EGR valves include a sensor that reports how far the valve is open.
TaT says P0406 sets when that signal is higher than expected, from a short to voltage, a faulty sensor or wiring.
PartsAvatar adds that carbon can keep the valve from moving and that damaged vacuum lines are also listed.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: EGR valve or position sensor fault
Common general cause- Why it ranks here
- Both sources list the valve or sensor.
- What would change this
- Rises if the sensor signal stays high with the valve at rest. Falls if the signal moves normally.
Cause 2: Signal wire shorted to battery voltage
Common general cause- Why it ranks here
- TaT and PartsAvatar both name a short to voltage.
- What would change this
- Rises if the signal wire reads supply voltage when the sensor is unplugged. Falls if it reads low when unplugged.
Cause 3: Carbon build-up or vacuum line damage
Possible — needs testing- Why it ranks here
- PartsAvatar lists carbon build-up and damaged vacuum lines.
- What would change this
- Rises if the valve is sooty or sticks or a line is cracked. Falls if the valve is clean and lines are sound.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all codes, note freeze-frame data, clear the code and test drive.
IfCode returns
It meansInspect wiring and the valve.
IfCode stays away
It meansIntermittent; monitor.
Step 2: Inspect the EGR wiring, connectors, vacuum lines and the valve for carbon.
Warning:The EGR valve is hot after driving. Let the engine cool first.
IfDamaged wiring or vacuum line is found
It meansRepair it.
IfValve is sooty or sensor signal stuck high
It meansValve or sensor suspect.
IfSignal wire reads supply voltage unplugged
It meansWiring short.
Symptoms
- Check engine light
- Engine surging
- Intermittent stalling Gets more serious: stop and have it checked.
How to fix
Step 1: With the engine off and cool, check that the EGR connector is seated and the vacuum lines are on.
On your vehicle
JeepYour car
2011–2013 · Grand Cherokee
Supported by vehicle dataJeep bulletin 08-008-15 names P0406. Reprogram the engine computer with new software for a small number of vehicles with the light on and P0405 and/or P0406 stored. Whether it is still current is not verified.
08-008-15Status unverified
ECM reprogram for P0405 / P0406 MIL on (Grand Cherokee)
2011–2013grand-cherokee · issued · NHTSA 10148595
Reprogram the engine computer with new software for a small number of vehicles with the light on and P0405 and/or P0406 stored.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
Related codes
P0406 questions
Do I need a new EGR valve for P0406?
Often, since PartsAvatar lists the valve or its built-in sensor, but check wiring and carbon first.
Sources and review
- P0406 OBD error code summary
- P0406 fault code entry
- Jeep 08-008-15: ECM reprogram for P0405 / P0406 MIL on (Grand Cherokee)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error