Code po 405 - 1998 Oldsmobile 88

Diagnostic Test Code (DTC) P0405 is defined by SAE J2011 as "Exhaust Gas Recirculation Sensor "A" Circuit Low".

The Powertrain Control Module (PCM) commands the EGR valve to open. It then monitors the circuit from the EGR pintle position sensor to see if the valve responded to the command. DTC P0405 sets when the EGR valve is commanded open and there is little or no voltage return to the PCM from the EGR pintle position sensor.

Failures of GM EGR valves are VERY RARE. I have been in this business for nearly 37 years and I still have enough fingers to count the number of these valves I have replaced. Don't get me wrong, they DO fail, it just doesn't happen very often.

Almost every time I have come accross this code, it has been the result of a faulty wire or connector between the EGR valve and the PCM. More often than not, I have found that the wiring harness has been chewed by rodents (visual inspection will verify if this is the case). Sometimes the wires break inside the insulation right at the EGR valve connector. You can give them a slight tug to prove this in most cases...you will see the wire stretch inside the insulation - or it will break the rest of the way off.

EGR Valve issue