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P0401 Diagnostic Trouble Code

Technical description

There is a problem in the Exhaust Gas Recirculation (EGR) system.

What P0401 really means

The objective of the EGR system is to reduce the amount of oxides of nitrogen produced as a byproduct of combustion. These oxides of nitrogen are produced when cylinder temperatures reach a very high level, usually under heavy load or wide open throttle where “pinging” or pre-detonation cause less than ideal combustion. In order to keep temperatures from rising to this point, the EGR routes exhaust gas back into the cylinders to cool down combustion. The EGR system in the majority of cars consists of several tubes, a valve, and several sensors.

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What causes a P0401 code?

Although nominally termed an emission device, the EGR system prevents damage to our engine during heavy use. Lead in the past, and octane now, are modifiers in gasoline that help prevent it from pre-detonating in the chamber before the spark plug turns on. Most people know this as engine pinging. Pinging will damage the engine and many times to the point of failure. Especially for those drivers who do not use the approved octane level for their car, the EGR can keep the temperatures from reaching this point.

What is the severity of a P0401 code?

Significant. Although not as pressing as a misfiring engine, an EGR problem should be looked at as soon as possible. Most of the time, these repairs will be completed the same day

What type of repair(s) is required to resolve a P0401 code?

Although some diagnosis will be needed, typically, there are two, possibly three culprits that plague an EGR system and carbon is the accomplice. The EGR valve stops working from age or carbon build up, the tubes become filled with carbon and restrict flow, or the sensor that monitors how hard the engine works goes bad.

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What is the cost to resolve a P0401 code?

  • Estimated part(s) cost: $50–$300
  • Estimated labor cost: $100–$400
  • Estimated total cost: $150–$700

Repair cost will vary across make and model. EGR valves come as either mechanical or electric with the former in the $100 to $150 and the latter in the $250 to $300 range. Sensors will be lower in the $50 to $75. Most labor costs for these parts will be on the lower end because the parts are easier to access, so somewhere in the $100 range or less will be common. The restricted tubes will get expensive. Despite the repair not needing any parts, the removal and cleaning of restricted tubes takes time, so expect a bill in the $300 to $400 dollar range.

If you vehicle is currently throwing this code, schedule a diagnostic check with a mechanic immediately. Don’t have a regular mechanic? No problem. Compare pricing and schedule an appointment with mechanics in your area with Openbay.

Service article written by an ASE Master Technician

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