P0407 A low rate of the sensor circuit B of the exhaust gas recirculation system

OBD-II Trouble Code - P0407 - Data Sheet

P0407 - Low signal in the exhaust gas recirculation sensor circuit B.

P0407 is a generic OBD-II code for an EGR voltage problem in which the signal sent from the circuit to the engine computer is abnormally low and does not match manufacturer's accepted parameters.

What does trouble code P0407 mean?

This code is a generic transmission code. It is considered universal as it applies to all makes and models of vehicles (1996 and newer), although the specific repair steps may differ slightly depending on the model.

There are different designs of exhaust gas recirculation systems, but they all work in the same way. The Exhaust Gas Recirculation Valve is a valve controlled by the PCM (Powertrain Control Module) that allows measured amounts of exhaust gases to pass back into the cylinders for combustion along with the air/fuel mixture. Because exhaust gases are an inert gas that displaces oxygen, injecting them back into the cylinder can lower the combustion temperature, which helps reduce NOx (nitrogen oxide) emissions.

EGR is not required during cold start or idling. EGR is energized under certain conditions, such as at start-up or idling. Exhaust gas recirculation is supplied under certain conditions, such as partial throttle or deceleration, depending on engine temperature and load, etc. Exhaust gases are supplied to the EGR valve from the exhaust pipe, or an EGR valve can be installed directly in the exhaust manifold. If necessary, the valve is activated, allowing gases to pass into the cylinders. Some systems direct exhaust gases directly into the cylinders, while others simply inject them into the intake manifold, from where they are then drawn into the cylinders. while others simply inject it into the intake manifold, from where it is then pulled into the cylinders.

Some EGR systems are fairly simple, while others are slightly more complex. The electrically controlled exhaust gas recirculation valves are directly computer controlled. The harness connects to the valve itself and is controlled by the PCM when it sees a need. It can be 4 or 5 wires. Typically 1 or 2 grounds, 12V ignition circuit, 5V reference circuit, and feedback circuit. Other systems are vacuum controlled. It's pretty straightforward. The PCM controls a vacuum solenoid which, when activated, allows the vacuum to travel to and open the EGR valve. This type of EGR valve must also have an electrical connection for the feedback circuit. The EGR feedback loop allows the PCM to see if the EGR valve pin is actually moving properly.

If the feedback circuit detects that the voltage is unusually low or below the specified voltage, P0407 can be set.

Note: this code is basically identical to p0405. The difference is that DTC p0405 refers to sensor "A" and P0407 refers to EGR sensor "B". Refer to the specific vehicle repair manual for the location of sensors "A" and "B".

Symptoms

Most engines do not require EGR systems to function properly as they are strictly compliant with emission regulations. This means that with a P0407 code, there is a high chance that the driver will not notice any symptoms other than the Check Engine light. In some cases, there may be a decrease in fuel consumption or slight fluctuations during acceleration.

Symptoms of a P0407 trouble code may include:

• MIL Illumination (Malfunction Indicator)

Causes of the P0407 code

While P0407 can be caused by ground problems or even a faulty engine computer, the root cause is usually the EGR valve itself. Other possible causes include:

• Faulty EGR vacuum solenoid valve
• Faulty EGR valve
• Short circuit in the EGR circuit
• Short circuit in the EGR circuit
• Bad wiring from the engine control unit to the EGR system
• Defective engine control unit
• Short to ground in EGR signal circuits or reference circuits
• Short circuit to voltage in the ground circuit or signal circuits of the exhaust gas recirculation system
• Bad EGR valve
• Bad PCM wiring problems due to abraded or loose terminals

Possible solutions

If you have access to a scan tool, you can command the EGR valve ON. If it is responsive and the feedback indicates that the valve is moving correctly, the problem may be intermittent. Occasionally, in cold weather, moisture can freeze in the valve, causing it to stick. After warming up the vehicle, the problem may disappear. Carbon or other debris can get stuck in the valve causing it to stick.

If the exhaust gas recirculation valve does not respond to the scan tool commands, disconnect the exhaust gas recirculation harness connector. Turn the key to the on position, the engine is off (KOEO). Use a voltmeter to check for 5 V on the test lead of the EGR valve. If there is no 5 volts, is there any voltage at all? If the voltage is 12 volts, repair the short to voltage on the 5 volt reference circuit. If no voltage is present, connect a test lamp to battery voltage and check the 5 V reference wire. If the test lamp illuminates, the 5 V reference circuit is shorted to ground. Repair if necessary. If the test lamp does not illuminate, test the 5 V reference circuit for an open. Repair if necessary.

If there is no obvious problem and there is no 5 volt reference, the PCM may be faulty, however other codes are likely to be present. If 5 volts is present in the reference circuit, connect a 5 volt jumper wire to the EGR signal circuit. The scan tool EGR position should now read 100 percent. If it does not connect the test lamp to the battery voltage, check the signal circuit of the exhaust gas recirculation. If it is on, then the signal circuit is shorted to ground. Repair if necessary. If the indicator does not illuminate, check for an open in the EGR signal circuit. Repair if necessary.

If the scan tool displays a 5 percent EGR position after connecting the 100 V reference circuit to the EGR signal circuit, check for poor tension on the terminals on the EGR valve connector. If the wiring is OK, replace the EGR valve.

Associated EGR Codes: P0400, P0401, P0402, P0403, P0404, P0405, P0406, P0408, P0409

COMMON ERRORS WHEN DIAGNOSING CODE P0407

Oddly enough, the EGR valve is not always the cause of the P0407 code, and it can be expensive to replace it hastily without a proper diagnosis. You should test the least expensive components first, such as the wiring and solenoid, before replacing the valve yourself. Cleaning is much cheaper than replacing.

HOW SERIOUS CODE P0407 IS?

A faulty EGR valve can increase your vehicle's emissions and affect its performance, but it usually doesn't cause serious side effects. You should check it out sooner or later, but a few quick trips with P0407 won't do any serious damage.

WHAT REPAIRS CAN FIX CODE P0407?

The most common repair for P0407 is as follows:

• Clear the code with a scanner and keep an eye on the code that will be returned.
• Visually inspect the EGR valve and associated wiring and vacuum lines for obvious problems.
• Clean the EGR valve, clear the code and see if the regulator works again.
• Check voltage and grounding, repair wiring if necessary.
• Check vacuum lines to EGR and EGR solenoid - repair if necessary.
• Turn the magnet on and off to check if it works properly.
• Replace the EGR valve.

ADDITIONAL COMMENTS REGARDING CODE P0407 CONSIDERATION

P0407 is not a panic-inducing engine code, but it should also not be ignored as EGR systems play an important role in reducing a car's carbon footprint. Most valves will be easy to find as they are usually located close to the engine intake manifold so that the exhaust gases can be recirculated. On some used vehicles, previous owners have removed these systems for convenience.

How to Fix P0407 Engine Code in 3 Minutes [2 DIY Methods / Only $4.53]

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