Q: 1998 Mazda protege: Had the EGR valve replaced, cleared the computer codes, still get the check engine light then a EGR problem co

asked by on March 27, 2017

Originally replaced EGR valve, cleared the code. Still getting check engine light with same EGR code P0400. What now?

My car has 203000 miles.
My car has an automatic transmission.

Code P0400 does not necessarily mean that there is something wrong with the EGR valve itself. The only way to condemn the EGR valve is to directly test it. In particular Code P0400 includes a circumstance where the EGR passages are simply blocked with carbon and thus little or no exhaust gases can flow into the intake manifold. Code P0400 also includes the possibility that the EGR valve is not opening due to no vacuum opening the valve from the EGR control solenoid. If the valve is electronically controlled, there could be a fault in the circuit. If your vehicle is equipped with an EGR temperature sensor, if the sensor is plugged with carbon, it can’t register a temperature change when the EGR valve is opened, signifying flow. The point is Code P0400 can never be interpreted as the EGR valve has failed. The only way to determine if an EGR valve has failed is to directly test the valve. To resolve this, that is perform a complete system diagnostic and find the root cause for the code having set, the recommended service is an EGR system diagnostic. If you request that service, the responding certified mechanic will get this fully resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

My car is idling very rough.

The idle air control valve is common for causing a rough idle in many cars, but it sounds like you have already corrected that. Another thing you may also want to check is the crankshaft position sensor. A crankshaft position...

Thermostat malfunction code read

The Code that was set might have been P0126. The engine cooling thermostat maintains optimal engine temperature. Inasmuch as the PCM can measure actual temperature from other sensor inputs (such as the coolant temperature sensor), the functioning of the thermostat...

The air conditioner and heater control panel has no power, no lights, nothing

Since you seem to get some temporary action by messing with the fuses, the problem may lie in the power distribution box. Underneath the fuse panel is a network of connections, some of which may overheat in an older car....

Related articles

Understanding the Mazda Oil Life Monitor and Service Indicator Lights
Car symbols, or dashboard lights, are a car service reminder. The Mazda Oil Life Monitor system indicates when and what service your car needs.
How to Replace an Exhaust Gas Recirculation (EGR) Cooler
Exhaust gas recirculation (EGR) coolers lower the temperature of the exhaust gas before it enters the car engine. EGR coolers are mainly for diesel.
A Buyer’s Guide to the 2011 Mazda Tribute
2011 2011 marked the final year of production for the Mazda Tribute, a compact SUV that shared a platform with certain Ford models. The Tribute managed to combine relative affordability with decent performance and a modicum of comfort while driving...