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Code P0404

05-02-2007, 07:49 PM
I have a 1999 Ford Taurus. My neighbor ran a trouble check on it yesterday and it showed code P0404. Does anyone know what that code means? TIA

05-02-2007, 08:02 PM
I don't see it listed???

05-02-2007, 08:18 PM
P04XX Auxiliary Emission Controls
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
P0410 Secondary Air Injection System Malfunction

Welcome to the forum, nice to have you with us.
I did some research and came up with this, but I don't know if it is right or wrong.

"Generally this code means that the EGR should be replaced but it can be debris in the EGR causing problems. You can try cleaning it to see if it will help/fix the problem.

From the service manual: "Important.
When this DTC sets, some EGR functions will be disabled for the duration of that ignition cycle. When repairs are complete, codes must be cleared and the ignition keyed off for at least 10 seconds to allow proper operation."

Huney1 again: I saw a lot of references to cleaning the EGR valve, so I'd do that first then go from there. Good luck.

05-02-2007, 09:22 PM
"Generally this code means that the EGR should be replaced but it can be debris in the EGR causing problems. You can try cleaning it to see if it will help/fix the problem.

Thank you! Do you know where the EGR is located in a 1999 Taurus?

05-02-2007, 11:35 PM
Yeah, I went back and looked again, this time with the light on, you're right..

05-03-2007, 03:12 AM

Definition: The EGR valve is the main emissions control component in the Exhaust Gas Recirculation system. The valve is located on the intake manifold, and opens a small passageway between the exhaust and intake manifold to allow a metered amount of exhaust to flow back into the engine. This reduces combustion temperatures and helps control the formation of oxides of nitrogen. The EGR valve is opened by the application of vacuum to its control diaphragm. Some also require a certain amount of exhaust back pressure before they'll open. On newer vehicles, the valve is electronic and uses one or more solenoids or a small stepper motor. The valve should remain closed while the engine is cold and at idle. It should only open once the engine has warmed up and is running at part-throttle. If the valve sticks shut (or is disconnected), NOX emissions will soar and detonation will often result (See Detonation and Spark Knock). If it sticks in the open position or fails to close all the way, it acts like a vacuum leak resulting in a rough idle, hesitation and possible stalling.

05-03-2007, 03:31 AM
Here's what it looks like and it should be easy to find. On my 03 it's on the right back of the intake manifold near the firewall. Looks like removing from underneath would be best, definitely work with a cold engine. (
This is a motorcycle but it shows the carb cleaner and nozzle.
Get a can of carburetor cleaner with a plastic tube nozzle and *gently* stick the nozzle in and spray it good. Carbon build up prevents the diaphram from doing it's job so let the carb cleaner sit awhile to dissolve the carbon then shake it out then spray it again and keep doing that until it's clean and the diaphram has free movement. You can use a Q tip but be careful not to poke a hole in the diaphram. Anytime you use a spray or solvent I highly suggest using safety goggles because solvents, cleaners and eye balls do not good bedfellows make. AARRGGHH! IT BURNS! <Like in, "The Exorcist'"> I never cleaned one so maybe someone can tell you a better way, but either way, cleaning it or replacing it, the old one has to come off so give cleaning it a try. If you can't get the diaphram freed-up parts stores have new valves and shouldn't cause you a financial disaster, my guess around 50 bucks. Get your friend to put it on 'cause shop labor would probably run 60 bucks.

TaurusKing: Yeah, I went back and looked again, this time with the light on, you're right.. ( HeHeHeHe . . . . Yup, I know where you're comin' from old Buddy.
You think it's bad now . . . . wait'll you're 66 . . .
Sometimes I have a hard time remembering the way home.

05-03-2007, 12:56 PM
Be sure to only insert the straw/Q-tip/cleaner into the valve portion of the EGR valve and not the vacuum port of the EGR valve. The valve portion is the metal portion that gets bolted to the manifold. As long as this is the only place you work with, you don't need to worry about puncturing the diaphragm.

If you have a vacuum gauge, you can apply vacuum to the vacuum port and open the valve, then let the cleaner do its job on the valve sealing surfaces. This will also help you make sure the diaphragm integrity is good (holds a vacuum).


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