I replaced egr valve on 04 duramax but keep geting P0404 code is there some elec sensor to replace?

Are you in California. Did you put aftermarket exhaust on the truck? California Duramax are configured differently and if you mess with the exhaust it trips an EGR code that will turn the SES light on. Now, on a truck configured for Minnesota or Iowa changing the exhaust trips a code but it wont turn on the SES light. So, do you have any mods?

The LB7 EGR valves are vacuum operated, unlike the LLY,LBZ,LMM which are electrically controlled. This is why a finger stick does not work with LB7's.

The most likely cause is the belt driven vacuum pump which is mounted below the belt tensioner. These do go bad and stop pumping vacuum. Usually they make a knocking noise when bad. You need to pull a vacuum hose off on top of the fuel filter the runs to the vacuum pump and check it for vacuum with the engine running. Should have at least 15 inches. If this is not the problem the it gets a little more complex from here.


P0404 - Exhaust Gas Recirculation Circuit Range/Performance

The EGR (Exhaust Gas Recirculation) system's purpose is to redirect exhaust gas back into the cylinders. Since exhaust gas is inert, it displaces oxygen and fuel, thereby lowering cylinder temps, which, in turn, lowers oxides of nitrogen emissions. For that reason it needs to be carefully metered into the cylinders (via the EGR valve) so as not to adversely affect the engine's performance. (Too much EGR and the engine won't idle).

If you have a P0404, then the EGR valve is likely an electrically controlled EGR valve instead of a vacuum controlled EGR valve. Also, the valve will usually have a feedback system built into it that informs the PCM (Powertrain Control Module) what position the valve is in; open, closed, or somewhere in between. The PCM needs to know this to determine whether or not the valve is operating as needed. If the PCM determines that the valve should be operating, but the feedback circuit shows that the valve is not open, this code will set. Or if the PCM determines the valve should be closed but the feedback signal indicates that the valve is open, this code will set.

Symptoms: There may be no symptoms of a P0404 DTC other than the MIL (malfunction indicator lamp) or check engine light. However, Exhaust Gas Recirculation systems are inherently problematic due to carbon buildup in the intake manifold, etc. This normal buildup can lodge in an EGR valve, holding it open when it should be closed. If this is the case, the engine may idle rough, or not at all. If the valve has failed and is NOT opening, then symptoms would be higher combustion temps and as a result, higher Nox emissions. But the latter symptoms aren't going to be noticeable to a driver.

Causes: Usually this code points to either carbon buildup or a bad EGR valve. However that doesn't rule out the following:
* Open or short in the 5 Volt reference circuit
* Open or short in the ground circuit
* Open or short in the PCM controlled voltage circuit
* Bad PCM (less likely)

Possible Solutions:
1. Using a scan tool command the EGR valve to open while watching the actual EGR position (it will probably be labeled "desired EGR" or something similar). The actual EGR position should be very close to the "desired" EGR position. If it is, then the problem is likely intermittent. It may have been a lodged piece of carbon that has since dislodged, or it could be a bad EGR valve winding that intermittently opens or shorts as the valve temperature changes.
2. If the EGR "desired" position is not close to the "actual" position, then unplug the EGR sensor. Check for a good 5 Volt reference voltage to the connector. If it doesn't show a reference voltage, repair an open or short in the 5 Volt reference circuit.
3. If there is a 5 volt reference voltage, activate the EGR with the scanner, monitor the EGR ground circuit with a DVOM (Digital Volt/Ohm meter). It should indicate a good ground. If it doesn't then repair the ground circuit.
4. If there is a good ground, then check the control circuit. It should indicate voltage that varies according to the percentage that the EGR is open. As it's open more, the voltage should increase accordingly. If it does, then replace the EGR valve.
5. If the voltage doesn't increase incrementally, then repair open or short in EGR control circuit.


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HI,

There has been a high percentage of No Trouble Found (NTF) 6.6 LLY ECMs being returned to the Warranty Parts Center. The No Trouble Found (NTF) ECMs are being replaced for a specific list of DTCs. Recommendation/Instructions: Please do not replace the 6.6 LLY diesel engine ECM without completing all of the proper SI diagnostics. Below is a list of DTCs that are appearing on the No Trouble Found ECM replacement repair orders: P0401 P0404 and P0299: EGR and Turbo Boost Trouble Codes For EGR codes and Turbo Boost codes that set with no customer driveability complaints, verify the vehicle has the latest TIS2000 calibration update named "diagnostic enhancements for P0401 and P0404." If the EGR and Boost codes can be duplicated and the codes are set with a driveability symptom, monitor and inspect the EGR valve for sticking.Since the valve was replaced and is operating correctly it would need the calibration update at the dealer . This would be the Next step.

PIP3346A: Diesel Engine ECM Replacement - keywords 6.6 6.6L alternator calibration charge DTC EGR generator LLY P0045 P0046 P0299 P0403 P0404 P0621 P0622 P2563 PCM SES turbo - (Jun 16, 2005). Yes it would be the same issue . I would start here next . Unless that valve is bad or the ports clogged .
Let me know,if needed further assistance.

Hope i helped you.

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