LS4 open loop fault switching at idle from closed loop, back and forth
06-29-2015, 04:27 PM
#1
LS4 open loop fault switching at idle from closed loop, back and forth Just put my LS4 07 grand prix GXP back together, removed the DoD system, threw in a 214/220 .540/.535 115+2 LSA cam, headers and intake. Car has been running fantastic, been doing alot of tuning, disabling things in the tune file like DoD, cat overtemp, changing idle settings to get the cam running smoother, etc. I noticed over the past 2 days ive been tuning that i seem to have an issue where the fuel trims turn off for some reason, narrowed it down to it switching been closed loop and open loop consistently, but fuel system status is displaying "FAULT" when it switches, and its not giving me any DTC's (P0300 disabled among DoD codes). This seems to happen more consistently while at idle, it will go for a minute in closed loop, then it will fault, then go back to normal, and I cannot figure out for the life of me why. Posting up a scan of what its doing and the tune file.
06-29-2015, 04:42 PM
#3
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The thing I've seen do this, is a flaky ECT sensor connector.
But I expect there could be others, like maybe EVAP / tank
pressure perhaps (I don't know much about newer models
than mine). Are there finer-grained fuel system status
indicators you can scan, maybe pin down the bad actor? I
dunno. But failing that, maybe look at the FTC when it's
dropped out of CL and see which open loop mode it's at
(cold, warm, EVAP purge active, etc.).
But I expect there could be others, like maybe EVAP / tank
pressure perhaps (I don't know much about newer models
than mine). Are there finer-grained fuel system status
indicators you can scan, maybe pin down the bad actor? I
dunno. But failing that, maybe look at the FTC when it's
dropped out of CL and see which open loop mode it's at
(cold, warm, EVAP purge active, etc.).
06-29-2015, 04:47 PM
#4
What additional things should I throw up in the VCM scanner to check, ETC sensor is brand new, along with the cam position sensor, replaced those when I rebuilt the engine. ECT seems to be spot on, and I went over the harness and verified all the wires were good, and reloomed everything. What's puzzling me is no pending codes. Ill go ahead and add some extra things to the scan and see what I can come up with.
06-29-2015, 05:01 PM
#6
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Not to hijack. But jimmyblue what should normal fuel tank pressure be? On my 09 g8 gt. I can't get the evap to read at all. But the evap pressure goes up to 3k pa I believe it says. It pegs my gauge on my tq. Pro app.
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06-29-2015, 07:55 PM
#8
figured out, apparently disabling the P0300 code does not prevent the system from setting a fault for it, increased the random misfire thresholds by 50% and dropped the total misfires from 120 down to 40 or so, and it went right into closed loop normal.