Hello everyone. Real quick been getting p0400 and p0410 recently. This is a 96 z with 153xxx it's fully maintained always all parts you name for maintenance is fairly new on it plugs filters etc..... I cleaned the egr and air connectors twice checked all connections lines evap canister etc still comes on but one at a time. Ex today egr tomorrow air. Only happens when on the highway various speeds or gears 5 or 6 mainly triggers. I do know and when the egr air work but it's annoying should I have it tuned out or fix. This has just recently been happening . Btw car is tuned with cats and rear 02 delete and other mods in all the years this never happened till now. Any help or suggestions would be great

 

P0400 sets when the PCM cycles the EGR valve and doesn't not see evidence of exhaust gas flow while looking for a change in the MAP reading. The diagnostic can only be run under relatively limited conditions - mainly at cruise when there is very little change in throttle position, RPM or MAP. Hence, only sets in your cruising gears.

Could be:
-cracked EGR vacuum lines
-plugged EGR solenoid
-faulty EGR valve
-dirty EGR valve pintle
-EGR passages in manifold blocked
-corrugated EGR riser tube from passenger side exhaust leaking
-low back-pressure exhaust system

It's not an electrical problem with the solenoid - there is a separate code for that.

P0410 sets when the PCM cycles the AIR pump, and does not see an increase in O2 content in the exhaust, or does not see lean O2 readings when the PCM is operating in open loop and the pump is supposed to be running. Make sure the pump is running - should run for a couple minutes at startup. Make sure there are no melted rubber elbows in the plumbing to the check valves. A leaking check valve will melt the rubber elbows. Check valves could also be rusted closed.

Again, not a problem with the AIR pump relay circuit. Separate code for that.

 

Injuneer all reasons you mentioned I checked thank you. I'm well verse on the on all problems that can be. But you are right p0410comes up only when cruising. I've cleaned both check valves and egr twice. Only happens at various highway speeds mainly in 5 or6 gear. And yes I have a low restriction exh. Borla cutback custom y pipe no cats or rear 02 sensors but in the 6 years it was tuned out now it appears. Btw have stock manifolds air injection and all egr on car. All work hear them and tested them. It's cheaper to eliminate than fix but why would they pop up now and be a pita with the ses light is my main problem

 

If you had included all that info in your original post, you wouldn't have got what you appear to feel is too simple for your "well versed" knowledge.

Good luck.