P0402: EGR A Flow Excessive Detected
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes - the engine may idle roughly or stall when coming to a stop.
Symptoms
- Rough idle or stalling at stops
- Hesitation from a standstill
- Emissions test failure
Likely causes, most common first
- EGR valve stuck open
- Carbon holding the valve off its seat
- Control solenoid stuck
- Faulty differential pressure sensor
Read P0402 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
P0402 means too much exhaust gas is being recirculated. Exhaust gas does not burn, so an EGR valve stuck open at idle is effectively a large vacuum leak filled with inert gas - the engine idles roughly and may stall as it comes to a stop.
The classic pattern is a car that runs perfectly on the motorway and stumbles in town, because at cruise the engine genuinely wants recirculated gas and at idle it wants none. A carbon flake holding the valve open is a common and cheap cause.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P0402
“Truck was consuming coolant and you could smell it but can't see a leak then the service electronic throttle control light came on a few weeks later with a code reading P0402. This was a recall and has been replaced but was replaced before they had the proper fix for it. Dropped it off at dodge dealer this morning for further diagnosis.”2017 Ram 1500 · Jun 2024
“At just 600 miles, the 2023 GMC Sierra 3.0 Duramax gave out a check engine light. The code reader displayed a P0402. The truck had a very strong fume odor. The truck was taken to service two times. GM engineering made tests on the truck and concluded that the truck needs to be reprogrammed. I have a case number established with GM (case number 9-9217617941). If the program is bad, why release the product to the public? See attached invoice for details. This issue is present on almost all LZ0 GMC trucks based on people I've met in forums. Please help us.”2023 GMC Sierra 1500 · Dec 2022
“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
Show 3 more owner reports
“My check engine light came on, so I took the car to the mechanic, they told me that I had an error p0402 catalytic converter malfunction. They told me that this is a known issue with the nissan altima and that nissan knows about it and does not care to anything about it; he told me to google it and see the number of complaints online from nissan altima owners. I did just that and was amazed at how many complaints there were. The repair shop said that they won't fix it for fear of making it worse and told me to get rid of the car!. *tr”2010 Nissan Altima · Jan 2015 · 93,000 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
“Check engine light goes on and off repeatedly with p0402 catalytic converter not functioning efficiently. Has been going on for two years. Passed smog.”2003 Honda CR-V · Dec 2013 · 169,000 mi
Cars that report P0402 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0402?
Yes - the engine may idle roughly or stall when coming to a stop.
How much does it cost to fix P0402?
Typical US repair costs range from $120 for the simplest fix (egr valve cleaning) 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 P0402. 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.