P0487 – Exhaust gas recirculation (EGR) system, throttle position control -circuit malfunction

By Georgi (Contact Me)
Last Updated 2016-07-20
Automotive engineer

Table of Contents

1. What Does Code P0487 Mean?
2. What are the common causes of code P0487 ?
3. What are the symptoms of code P0487 ?
4. How do you troubleshoot code P0487 ?
5. Codes Related to P0487
6. Get Help with P0487

What Does Code P0487 Mean?

The P0487 means that the engine control unit (ECU) is detecting a problem with the rate of exhaust gas recirculation (EGR) system flow or does not detect voltage to the EGR solenoid circuit.

This trouble diagnostic code is composed by two parts. The first part is faulty EGR valve or problem with wiring harness (open or short circuits, broken wires, damaged or corroded connectors). The other part is related to throttle position control circuit. Modern cars use the so called “drive by wire systems”. In this system the throttle pedal and throttle plate are not connected mechanically, but electrically. In the pedal there is potentiometer which follows the position of the pedal and sends a signal to an electrical motor positioned in the throttle body. In this arrangement you have a lot of electrical components and connections which can be source of the problem.

What are the common causes of code P0487 ?

Some common causes leading to P0487 code are clogged or blocked EGR and DPFE (this is delta pressure feedback EGR, system used by Ford) passages and sensors, faulty EGR sensor, MAP sensor, faulty EGR valve, faulty EGR control solenoid, a broken vacuum line, or faulty wiring harness or connectors.

Common misdiagnosis for this code is assuming immediately that the EGR valve itself is faulty and replace the expensive part. The EGR valve fails much less than the other components related to its operation.

What are the symptoms of code P0487 ?

In the early stage, you won’t see any symptoms. The code will be stored in the ECU, and it might take few starts until the service engine lamp lights up.  In some extreme cases, you will feel a significant difference in the performance of your vehicle.

If the EGR is stuck closed, the car will start to knock and increased nitrogen oxide will be present. When this kind of knocking is present over a period of time, you can check you EGR by warming up you engine and rev it. While revving, monitor the EGR for movement.

EGR stuck open. This will lead to major vacuum leaks. This will cause inefficient combustion, hesitation, rough idling and even stalling. Open EGR valve allow excessive amount of exhaust gases to enter the combustion chamber and disrupting the air fuel mixture, preventing it from burning properly. To test this case, leave the car idling with the hand brake on and examine to EGR shaft.

You can experience other symptoms like: detonation, stalling, hard starting and rough or misfiring idling.

How do you troubleshoot code P0487 ?

There are two main EGR systems available for commercial vehicles. The first one is operated by engine vacuum and the second is operated by small electrical motor(s). The vacuum system can be divided into two sub systems. The common here is the valve actuator which is the same for the two systems. The difference is that in the only vacuum system the vacuum from the engine directly moves the valve diaphragm.  In the other system, solenoid valves are used to control the amount of vacuum.

In the system controlled by electric actuator, the valve is directly attached to the valve and its position is controlled by varying degree of voltage send by the ECU. The ECU uses data from various sources like: throttle position sensor, vehicle speed sensor, mass air flow sensor, and the oxygen sensor helps to determine the position of the EGR valve. To determine if the EGR flow is correct the ECU uses several additional values gathered from: manifold air pressure sensor, barometric pressure sensor, and delta pressure feedback EGR sensor if equipped.

To perform proper diagnosis of this code, you will need a quality scanner suitable for your vehicle and digital multimeter, hand held vacuum pump.

Start with visual inspections the vacuum hoses and wires involved in connecting the EGR with the other components. If you find hoses that are unplugged or cracked replace them. Same with the wires and connectors, if there is shorts or broken wire repair them. When you are ready inspecting vacuum hoses and electrical connections, erase all the error codes and test the system. If TDC are still presented write them down and freeze frame data.

If the condition is intermittent this can point to a problem with: EGR or DPFE sensor, suspect loose, corroded or brunt connections, sticking EGR valve, or EGR control solenoid.

Now you need to check the operation of the EGR and the passages in the body. Over time and with the increase of the mileage of the vehicle the carbon from the engine starts to build up inside the valve housing and to clog the passages. To check this disconnect the vacuum hose operating the EGR and connect the hand vacuum pump. Start the engine. While the engine is idling apply vacuum to the EGR valve using the pump and observe the operation of the EGR. If the EGR opens and the engine continue to work without stalling, the some or all passages in the housing are blocked by carbon build up. If this is the case remove the valve, locate the discharge holes and remove all the carbon from the passages and the housing of the valve. If the valve fails to operate under vacuum replace the whole unit. If the engine stalls after the valve opens, check the vacuum to the EGR solenoid.

Now we move to the EGR solenoid. If you have vacuum at the inlet, you need to check for vacuum on the outlet. To do this disconnect the output while the engine is running and activate the solenoid with the scanner tool. If the solenoid is not faulty you must hear tick sound from it and vacuum on the outlet must be presented. If you don’t hear the tick or see vacuum test the connector for voltage or ground. If they are not presented disconnect the ECU connector and test for continuity. If you find open or short circuits repair them.

If the system is from the second type, operated by a small electric motor, activate the EGR while the engine is idling and if the engine does not stall unbolt the EGR and test it to if moves. Some models will need additional grounding after you remove the housing from the engine. If the fault is in the valve, replace it erase the codes and test the vehicle. If the EGR operates remove it from the engine and live it aside. Try to start the engine if the is not starting or start and idle bad, that means that the EGR passages are free of obstructions, if the engine starts and idle normally, you have clogged EGR passages. To clean the EGR use chemical agent, be sure to check the manufacturer recommendations. If EGR is operating and the engine stalls sets the voltage signal from ECU to EGR. Make note of the voltage readings and check them with the one specified by the manufacturer, because some uses multiple servos for activation. If there is difference is the voltage readings disconnect the ECU connector and test the harness for proper resistance and continuity. Repair short or broken wires. Reset the codes and test the vehicle.

Throttle Position Control Circuit

In most cases the reason for this code is the EGR valve, but in some cases after cleaning or replacing the valve the code is still presented. To find the problem you need to investigate the throttle position control circuit. To do this you will need: code reader, digital multi-meter, and the wiring diagram of the circuit.

1. Start by visually inspecting the pedal and the throttle body. Look for free movement and no binding. Check the wiring harness and the connectors. If everything is OK move on.
2. Locate the throttle body and remove all the plastics covering it, so you can see the throttle plate. You need someone to start the car and depress the throttle pedal while you observe the movement of the throttle plate. If there is something unusual, check the throttle body and the pedal position sensor.
3. To check the throttle body by searching the manual or the internet to find which pins you meed to test with the multi0meter.
4. On the wiring harness from the throttle pedal should have to pins with resistance which change according to the position of the pedal. Find them and measure the resistance by depressing the pedal all the way. The reading must be smooth without and interruptions. If there is some kind of interruption the problem might be in the potentiometer itself, if you can get any reading at all you need to check the harness.
5. Check the wiring harness for continuity suing the digital multi-meter. Inspect the harness for opens, shorts ,broken or cracked wires. If you find any repair them before you move on.
6. In the throttle position sensor there is path and follower which determine the position of the pedal and sends signal to the throttle body. Sometimes the path which is made out of graphite can ware out or dirt and grease can contaminate it. If this is the case remove the pedal and examine the sensor.
7. Clean the outside of the sensor before you open it. After you open it check the graphite path if there are sign of ware, you might need to replace the whole pedal assembly. For some models you might find replacement graphite path. If the path is contaminated use soft cotton buds and alcohol and carefully clean the contaminations.
8. Reinstall the throttle and make a test drive.
9. If the problem is still present you may have faulty throttle body actuator and replacing might be needed.

Codes Related to P0487

• P0382 Exhaust Gas Recirculation Flow Malfunction
• P0400 Exhaust Gas Recirculation Flow Malfunction
• P0401 Exhaust Gas Recirculation Flow Insufficient Detected
• P0402 Exhaust Gas Recirculation Flow Excessive Detected
• P0403 Exhaust Gas Recirculation Circuit Malfunction
• P0404 Exhaust Gas Recirculation Circuit Range/Performance
• P0405 Exhaust Gas Recirculation Sensor A Circuit Low
• P0406 Exhaust Gas Recirculation Sensor A Circuit High
• P0407 Exhaust Gas Recirculation Sensor B Circuit Low
• P0408 Exhaust Gas Recirculation Sensor B Circuit High

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