P0406: EGR Sensor A Circuit High
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes - driveability is often normal, but the fault will not clear itself.
Symptoms
- Check engine light
- Rough idle in some cases
- Emissions test failure
Likely causes, most common first
- EGR position sensor signal shorted to voltage
- Failed position sensor inside the valve
- Wiring damaged by engine bay heat
- Corroded connector
Read P0406 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0406 reports the EGR position signal stuck at the high end of its range - a voltage that would mean the valve is wide open when it should be shut. On most modern designs the position sensor is built into the valve and cannot be bought separately.
Before accepting that expense, check the harness where it passes near the exhaust manifold. Heat-hardened insulation cracking against a hot surface is a recurring cause of high-voltage faults in this circuit, and a wiring repair costs a fraction of the valve.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0406
“Severe bucking & jerking while driving. More moderate bucking while car is idle. Codes being thrown are p0406 & p0301. It has also thrown a p0402 as well. I've replaced the egr valve as well as all spark plugs and the problem still has not been solved. My fuel mileage is tanking and driving the jeep has become almost unbearable.”2016 Jeep Grand Cherokee · Jul 2020 · 94,000 mi
“Got a technical service bulletin code p0406 and ask local dealer if they could repair this emission problem. They said no. Engine light comes on regularly and getting bad fuel mpg. Also codes p0404 and p0405 was recorded.”2007 Dodge Ram 1500 · Feb 2017 · 69,000 mi
“Lack of power or runs rough condition, and/or the malfunction indicator light on with egr related diagnostic trouble codes (p0401, p0402, p0403, p0404, p0405, or p0406). Engine and engine cooling:exhaust system:emission control:gas recirculation valve (egr valve). *tr”NHTSA complaint · Mar 2014 · 40,000 mi
Show 2 more owner reports
“While driving on the freeway, the vehicle suddenly shifted itself into 3rd gear. Paddle shifting was inoperable and vehicle will up or down shift. Error codes given are p0700, and p0406. Problem seemed to resolve after restarting vehicle, but then shifts again after a couple of minutes. Now vehicle stays in 3rd gear permanently. Fluid levels ok, guessing it is electrical/computer related issue based on internet research. Taking to dealer soon to have final drive controller new software installed based on recall #n23. Hoping it is related to that issue. *tr”2005 Jeep Grand Cherokee · Dec 2013 · 65,000 mi
“2005 dodge ram 1500 quad cab 4.7l v8. 3-4 times / week the engine stalls while driving less than 10 mph, usually while slowing down to stop and sometimes while accelerating slowly. Check engine light is on with engine codes p0404 & p0406 set (egr valve) talked to service department at dodge dealership. They said that this is a common problem with this model and that dodge isn't doing anything to correct it unless I pay to have them fix it. The egr valve apparently has a design flaw and prone to fail. *jb”2005 Dodge Ram 1500 · Feb 2006 · 29,000 mi
Cars that report P0406 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0406?
Yes - driveability is often normal, but the fault will not clear itself.
How much does it cost to fix P0406?
Typical US repair costs range from $60 for the simplest fix (egr valve) to $700 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0406. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.