1996 CHEVY BLAZER, 220,000 MILES.

p0300 Random misfire, and p1406 egr pintle position circuit malfunction

This would be the 3rd EGR valve purchased from Advanced Auto in a years time. My ses light was burnt out so I didn't realize I had these codes pop up until I noticed it running rough. Have screened gasket. Last time changed had same codes, and noticed some corrosion on EGR connector so we replaced connector and warranted out the EGR valve. Vehicle ran much better with more "spunk" for about 1 month.

We pulled a wiring diagram and started checking for any corrosion or breaks. Tested for resistance on with all 5 wires at pcm, and all tested out good (.5-.7ohms), except, we accidently checked ohms between the grey 5 volt reference wire at the pcm to the ground wire at the connector and got like 180.5 ohms of resistence. What I had found through the wiring diagram is that the 5 volt reference wire shares with the map sensor and the fuel pressure sensor, and that ground shares with almost 5 different sensors. We did find a vacuum disconnected at the map sensor, and it's been disco'd for quite a while. Is that the cause of my EGR issues?

 

P1406 is an electrical circuit problem. Extremely rare for the EGR valve to set this DTC. This link will help: https://blazerforum.com/forum/diagno...plained-39054/

Running better for a month: It could be that when you replaced the connector, you disturbed the wire harness enough to make a good connection. Just a thought.

The P0300 is indicating a misfire, probably not related to the EGR problem.

EDIT: The pink wire must show battery voltage in START and RUN positions. The other 4 wires go directly to the PCM, no other wires splice to them.