Exhaust Gas Recirculation Flow Excessive Detected

Severity

Low

Can I keep driving?

Usually drivable; have it fixed at the first opportunity.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Read live data on EGR commanded vs actual position, the gap tells you whether the valve is responding correctly 2. Remove the EGR valve and inspect for carbon buildup that might be preventing full closure 3. Try cleaning if accessible (EGR cleaner spray £8) and check whether the valve seats properly when commanded closed 4. Test the actuator electrically against spec, resistance and operation against manufacturer values 5. Check vacuum lines on cars that use vacuum control 6. If cleaning doesn't help, valve replacement is the typical fix

PPowertrain
0Generic code
4Emissions
02Sequence number

What does it mean?

A malfunctioning EGR system will cause several codes such as P0400 or P0401-P0409 to be displayed. Often a P040x code is caused by a blockage in the EGR system and is not caused by a failed component. Possible Problems with the EGR System Most common problem – carbon blockage where the EGR valve connects to the intake manifold Leaks in the vacuum lines EGR solenoid not opening or closing How does the car’s computer detect a P040x code?

A typical OBD-II test sequence is shown below: For a P0401 (insufficient flow) or P0402 (excessive flow) the PCM will monitor the following components during the test sequence shown above: EGR valve pintle position – if the EGR valve is electrically controlled MAP sensor – if the EGR valve is vacuum controlled the PCM will read changes in the MAP sensor output in response to exhaust gas recirculation. The voltage from the MAP should increase when the EGR valve is opened.

EGR Components Above is a diagram of an exhaust gas recirculation system (Ford with DPFE). The exhaust gas recirculation (EGR) system has a few primary components: EGR Valve – recirculates exhaust gas through the intake manifold. EGR Solenoid – the “brains” of the EGR system Vacuum Line – present in vacuum operated systems EGR Tube – intake for exhaust gases DPFE – stands for Differential Pressure Feedback for EGR

Symptoms

Likely causes

How to fix it

Codes From the Same System

All Fault Codes

Related Similar Codes

This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.