Error Code P0486 is defined as Exhaust Gas Recirculation Sensor “B” Circuit. This code is a generic trouble code, which means it applies to all vehicles equipped with the OBD-II scanner, or vehicles made since 1996 up to present. It is, however, more common among Mazda and Mercedes Benz vehicles. Specifications on the definition, troubleshooting and repairs, of course, vary from one make/model to another.

This code relates to a problem in the “B” electrical circuit to the EGR (exhaust gas recirculation) valve.

The EGR valve works by introducing a regulated amount of exhaust gas into the intake manifold. This process is necessary to keep the temperature of the cylinder below 2500˚ F, as NOx (Nitrates of Oxygen) form when the temperature rises more than 2500˚ F. Nox is harmful to health and the environment, as it’s responsible for smog and air pollution.

The controlling computer (PCM or powertrain control module, also known as ECM or engine control module in other vehicle makes) sets this code when it detects an abnormally low, high, or non-existent signal voltage.

Error Codes P0486 is very similar on all vehicles, but since different vehicles will have different types of EGRs, sensors, and activation methods. The only similarity will be is that they all vent exhaust gas into the intake manifold to cool the temperature of the cylinder heads.

Introducing used and spent exhaust gas to the engine at the wrong time reduces horsepower, causing the vehicle to stall, or have a rough idle. Thus, computer programming only opens the EGR when the RPM of the engine goes above 2000 and to close when under a load.

Related EGR Error Codes include:

  • Error Code P0400
  • Error Code P0401
  • Error Code P0402
  • Error Code P0403
  • Error Code P0404
  • Error Code P0405
  • Error Code P0406
  • Error Code P0407
  • Error Code P0408
  • Error Code P0409

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. In some cases, this code can be accompanied by other EGR related codes. Error Code P0405, for example, means there is low sensor voltage, while the P0406 means high sensor voltage. Other symptoms include:

  • Stuck open or partly open EGR pintle
  • Vehicle does not idle or stall
  • Pinging sound when vehicle is under load or high RPM

Possible Causes

There are many possible causes for this code. Some of the most common causes are:

  • Faulty EGR sensor “B”
  • Fault in the wiring harness to the sensor
  • EGR pintle stuck in the closed position causing carbon buildup, which keeps it from opening
  • Lack of vacuum to the EGR solenoid
  • Faulty EGR solenoid
  • Faulty EGR position sensor
  • Defective differential pressure feedback EGR sensor

How to Check

All EGRs work the same – they re-circulate exhaust from the exhaust to the intake manifold. Obviously, they differ in methods for regulating the opening of the pintle and its sensing position.

The repair procedures we have here represent the most common problems accounting for the majority of EGR system failures. Fault in the wiring harness or sensor definitely requires the service manual to determine the specific wires and the necessary diagnostic procedures.

Remember that wiring differs from one manufacturer to another, and the computer will not react well if the wrong wire is probed. Also, probing the wrong wire may send excessive voltage to the computer’s sensor input terminal, which may fry the computer.

Simultaneously, when the wrong connector is disconnected, the computer may lose all of its programming, which may keep the vehicle from starting until the dealer reprograms the vehicle’s computer.

As its definition suggests, this code relates to a fault in the “B” circuit. Thus, make sure you check the EGR sensor connector and look for signs of damage, such as bent or pushed terminals, loose connections, or corrosion. Clean any corrosion off and re-seat the connector.

Take out the electrical connector and the EGR. Look for signs of coking in the EGRs intake and exhaust. Clean out any coking as necessary, so the pintle will move up and down smoothly.

Check the vacuum line from the EGR to the solenoid and replace it if any defects are found.

Check the solenoid electrical connector for corrosion or defects.

For Ford vehicles, follow the two vacuum hoses from the EGR to the differential pressure feedback EGR sensor (DPFE) in the rear of the manifold.

Check the two pressure hoses and look for any signs of corrosion. Most of the time, carbon builds up in these hose plug which leads to clogging. Use a small pocket screwdriver or equivalent and clean the hoses of corrosion and the sensor will begin to operate again.

How to Fix

Depending on your diagnosis, common fixes for this code are:

  • Repair or replacement of damaged or corroded wires, harness, or connectors
  • Clean out any coking as necessary, so the pintle will move up and down smoothly
  • Repair or replacement of defects in the vacuum line
  • Replacement of corroded electrical connectors

If the most common tests failed to solve the problem, a service manual is needed to continue to test the wiring circuits. The best solution is to take the vehicle to a service facility with the proper diagnostic equipment. They can quickly identify and repair this type of problem.