I searched the Isuzu forums, but this didn't come up. Got the CEL with P0401 about 6 months ago. Cleaned things up like the FAQ said, and the problem went away. Now I'm getting CEL P0405 (low EGR sensor voltage). Where is this sensor? Is it a part of the actual EGR valve, or someplace else on the manifold? I checked/cleaned the electrical connector to the EGR valve, but no dice. Any other suggestions? Thanks.

This info is from Alldata

The powertrain control module (PCM) monitors the EGR valve pintle position input to ensure that the valve responds properly to command from the PCM. If current pintle position voltage indicates less than 0.1 V and last more than 10 seconds , then the PCM will set DTC P0405

You may have a short in the wiring harness on the egr valve or you may have carbon build up around the pintle of the egr vavle which is causing it to stick. I know you said you cleaned it but i would take the egr valve off and make sure that pintle moves freely. If not spray carb cleaner until it does.