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GM hell?
Posted to Technical Discussion Forum on 1/23/2013 31 Replies

Hi everyone!

I've worked on GMs for 28 years, and they usually cooperate with me, but today, I have two in a row that are causing me grief!

Could I bother you people for a couple of minutes to help me brainstorm? I need a fresh perspective on these, and maybe some of you have had similar problems that you solved.

1) 2001 Impala 3.8L VIN K. Sets a P1404 for closed EGR performance. Customer brought it in with a new linear EGR valve installed, and the same code that it had before the 'repair'. On my Genisys, EGR minimum learned voltage is 0.24, and actual minimum voltage is 0.73. The valve passes the bi-directional functional test, but I can't figure out how to trigger the PCM to 'relearn' the new minimum. I have tried: 10-minute batt disconnect, DTC clear, crankshaft relearn, EGR disconnect and reconnect with KOEO, and a couple of others, in no particular order, but I can't get rid of that dang 0.24. Do I need a TECH 2?

2) 1987 Chevy R30 7.4L VIN N. Won't go into closed loop, even after thermostat install. O2 reads 0.00 at idle, and 0.98 at 2500 rpm. Coolant 190F. BLM and Integrator both stuck @ 128, always. No codes. I tried repeatedly goosing the throttle to generate some cross-counts, but no dice ... always OPEN loop. Are you aware of any PIDs other than the obvious that could prevent CLOSED loop, or am I barking up the wrong tree altogether?

Thank you, kind people,

Michael Barry
Quick Stop Smog & More
Sacramento, California, USA

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