96 Tacoma p0401

Just replaced the catalytic converter on my 96 2.7 Tacoma. Which got rid of the p0420 code I had. Now I have a new problem. I'm having a very rough idle for 10-30 seconds after startup and got the p0401 EGR insufficient flow code. Any ideas on what to check first?

 

How long before the EGR code is triggered; can you get the freeze frame so we can see everything else when the code was triggered.

 

Yeh here is the freeze frame data.

 

Was the engine warmed up at this time. Either the temperature sensor is registering low (I would think it would register a different fault in that scenario)

or the valve is getting stuck closed or partially closed.

maybe the switch has failed or the vacuum tubes are leaking. Ill have to check the routing on mine to think it through.

 

Yea it was warmed up. When I reset the code it took a little bit of driving for it to come back. I checked for vacuum leaks, seems to be all good. Someone else told me it maybe the switch also. How would I test that?

 

Sorry it’s been crazy lately; I’ve been meaning to search the field service manual to see how to test but been forgetting to. I have access to a pressure sensor and my best guess at how to test would be to measure the pressure going to EGR. I’ll have to trace the tubes back to the source but I assume it works off of engine intake vacuum. I would assume that the switch is normally closed meaning that when there is no power to it it closing the mechanical device in it that lets vacuum through or not.

When I bought my exhaust manifold it came with a blank off plate for the piping going to the EGR. Also, I believe LCE sales a blank off kit; I wonder how those kits avoid CEL’s? Do you need the light to go away to pass emissions or does it just bother you?

I’ve been working on a lean code issue which I think is vacuum leak related; I’ve wondered if it could be something wrong with the EGR or components.

 

When the engine has warmed up is the EGR valve or line hot? If not I would start diagnosing the temperature sensor. Is your intake air temperature sensor reading fine (it said it throws the code when the difference in the temperature of the intake and the EGR gas line it throws the code).