PO404 code- is it serious?


workman1
12-12-2006, 08:08 PM
Hi. I have a 98 Chevy Blazer LS Automatic. My check engine light came on and I used a tool to find that I have a DTC of PO404. I've read this has to do with the EGR valve system.

My question is, is this a serious fault that I need to get fixed soon? Might it cause the car to stop while driving? I can't afford to take it to the dealer to have looked at at this time. So if it's not serious I'll wait. If anyone can help with an answer I'd be grateful. Thanks. :)

Chris Stewart
12-12-2006, 09:41 PM
Ok Workman1,
I did some searching and found this in of all places, A Ford diesel site but since OBDII codes are Govt. stardardized, well here goes.

P0404 EGR Exhaust gas recirculation control circuit range/performance. Difference between command and actual exceeds a specified limit

Another search concerned a Grand Prix in which poor performance lit the Service Engine Soon light and produced a P0404 DTC. Their problem was solved with a catalytic converter replacement indicated by removing one of the O2 sensors from the exhaust pipe between the motor and catalytic converter which allowed the engine to breathe and perform much better. It also supports the Ford explaination.
I guess the EGR passages could clog enough to cause a difference between actual EGR flow and flow rate commanded by the computer.
Of course it could be a one time deal where resetting it or a number of good starts or run cycles will turn it off anyway.
Does it run good?

workman1
12-13-2006, 09:52 AM
.
Of course it could be a one time deal where resetting it or a number of good starts or run cycles will turn it off anyway.
Does it run good?

Thanks Chris. It seems to run well but I suppose I will have to keep an eye on that the next few days as the light only came on yesterday. Are you saying you think it might correct itself anyway with time?

mike2004tct
12-13-2006, 03:09 PM
Thanks Chris. It seems to run well but I suppose I will have to keep an eye on that the next few days as the light only came on yesterday. Are you saying you think it might correct itself anyway with time?

If it were the EGR valve, they are relatively easy to remove and clean. You can try it and see if your SES light goes off, but usually when an EGR is bad, the engine will buck at steady speeds. (and they are pricey)

To clean it, disconnect the negative battery cable, disconnect the plug at the top of the EGR, remove the 2 bolts securing it, then tip it upside down and inspect the pintle needle and opening. Remove any carbon build-up,, and make sure the pintle needle still moves up and down.
re-assemble the EGR, reconnect the battery, and see what happens.

workman1
12-13-2006, 05:51 PM
If it were the EGR valve, they are relatively easy to remove and clean. You can try it and see if your SES light goes off, but usually when an EGR is bad, the engine will buck at steady speeds. (and they are pricey)



Thanks for your advice. Today the SES light had gone off by itself. Should I still try to clean the EGR valve or does this mean it has sorted itself out?

Chris Stewart
12-13-2006, 09:56 PM
Sounds like it satisfied the computer so the light went out. If it starts setting the code again, a cleaning like mike2004tct mentioned would be something I'd try.

mike2004tct
12-13-2006, 10:23 PM
Sounds like it satisfied the computer so the light went out. If it starts setting the code again, a cleaning like mike2004tct mentioned would be something I'd try.
I agree.
If the light went out, no need to fix anything. It might've been water in the gas causing the light (I had that happen a few years back).

workman1
12-16-2006, 09:57 AM
Thank you all for your help. I appreciate it.

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