No items added
Customer Login Register Free

EGR Valve Diagnostics

Diagnostics, testing, removal and installation of EGR valves should always be carried out by suitably qualified persons.

There are several ways to troubleshoot an exhaust gas recirculation system.

  • Ensure you have identified the type of EGR valve on your vehicle.
  • Remove and inspect the EGR valve if you suspect a problem.
  • Examine the EGR valve and refer to the owners service manual so you can use the appropriate test procedure.
  • Follow the EGR troubleshooting procedure that's detailed in the owners service manual for your vehicles engine.
  • Many failures in older style EGR valves are caused by a rupture or leak in the valve diaphragm (where fitted). This is less common these days and 90% of EGR valves don’t have a diaphragm.

When an EGR valve that is stuck in the open position

When the EGR valve is stuck open this leads to a hot exhaust gas vacuum leak, which is worse than a standard vacuum or air leak because the EGR valve is not closing and is leaking exhaust into the intake manifold. This will cause reduced performance and driveability problems including hard starting, rough idle, stalling detonation (knocking or pinging). The reason for this is that the car cannot combust efficiently on the extra carbon dioxide emitted from the exhaust manifold, affecting the air / fuel mixture.

One way that may help you check if the EGR valve is stuck open is by measuring the EGR valve temperature, if it is hotter than the engine this may indicate that exhaust gas is constantly passing through the open EGR valve, causing exhaust pipe temperatures through the EGR valve and into the engine intake manifold. An Intake Air Temperature sensor mounted directly on the inlet manifold can quickly identify a leaking EGR valve due to rapid increase of air temperature when the engine is started.

Don’t ever touch the HOT EGR Valve, use an Infrared Thermometer (Check our accessories page – EQP-102 Automotive Multimeter and Infrared Thermometer)

(Click to enlarge)

When an EGR valve is stuck in the closed position

If the EGR valve is stuck closed it will significantly reduce effectiveness to control emissions and may bring on the engine warning light, and log a fault code.

An EGR valve that is stuck in the closed position will raise the temperatures and pressure in the combustion chamber, possibly creating a knocking (or pinging) as a faster explosion occurs in the cylinders. A knock can occur when the fuel in the combustion chamber ignites before the explosion in the cylinder reaches it. The noise is the sound of early ignition of the fuel when it meets high temperatures. This may be especially noticeable in situations where the vehicle is accelerating or cruising. This can lead to a disruption in engine timing and the vehicle may deliver reduced performance and driveability problems.
EGR valves stuck in the closed position are especially dangerous for vehicles equipped with turbos since the high temperature and constant exposure may eventually cause the turbo to seize.

A simple way to check if this is happening is to warm up your engine and increase the RPM, then check if the EGR valve has moved.

Diagnosing a Closed EGR Valve will require a Code Reader (Check our accessories page – AL301 Autolink Code Reader) or even better a diagnostic tool with the function to operate the EGR valve to test its valve is moving, (Check our accessories page- EQP-115 Electronic EGR, Throttle Body & Actuator Tester) this condition can be accompanied with OBDII trouble codes P1406 or P0401. You may also find a P0300 random misfire code on OBD II vehicles.

On late model computer controlled engines, there may be trouble codes that relate to the EGR system. On such an application, the first step would be to read out the code or codes using a scan tool or code reader. If you need a code reader-scanner or any other tools for testing or installation (Check our accessories page – AL301 Autolink Code Reader)

Example EGR Valve Trouble Codes:

On 1995 and newer vehicles with OBD II, P0400 to P0409 codes (Generic codes used as an example) can indicate various faults in the EGR system.
P0400....Exhaust Gas Recirculation Flow
P0401....Exhaust Gas Recirculation Flow Insufficient Detected
P0402....Exhaust Gas Recirculation Flow Excessive Detected
P0403....Exhaust Gas Recirculation Control Circuit
P0404....Exhaust Gas Recirculation Control 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
P0409....Exhaust Gas Recirculation Sensor 'A' Circuit
P0300....Random misfire (may also be caused by faulty EGR valve system)
These examples may suggest a fault in the EGR valve circuit / wiring or a faulty EGR valve. Trouble code P0409 for example, “EGR Valve Position Signal Error- Sensor 1”. Basically this can imply that the EGR valve position signal is lower or greater than the pre-mapped parameter expectations, and further investigation and verification is required before the EGR valve is replaced.
Individual cases can differ so recommends diagnostics and testing of EGR valves should always be carried out by suitably qualified persons.

EGR Electronics circuit fault

This includes the electronic activation and/or feedback system of the EGR, when this system is faulty the engine check light will be illuminated and usually is the first sign that something is wrong. Testing can be quite involved and we only recommend suitably qualified persons do this who have equipment like a scanner with EGR activation and test ability.
Repairing EGR valve electronics is not usually possible as manufactures seal the EGR valves so they cannot be tampered with.



Ignition Leads O2 Sensors