need help diagnosing my terrible misfire!
10-09-2011, 03:39 AM
#11
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did you check your wiring harness/connector for the O2? Do you know how to enable SD mode? Did you try to swap left and right sensor to see if the problem follows?
10-09-2011, 03:49 AM
#12
how can I load a file so you can read it?
You sent me that PM but i'll just write everything in here. I have to figure it out and maybe someone can chime in too, lol. The plug connector was good. No I don't on the SD, I know I have to disable the MAF and PE and what not. The sensors are new, Bank 2 has always given me problems since I did LT's even on the old 4.8. I checked the entire loom for pinch/burn marks and never seen one. I was thinking it was ground related but I am positive I have everything hooked up
well, I have been getting low voltages DTC's for Bank 2 sensor 1
B1S1 reads around 700ish mV, and dips down some
B2s1 reads around 300ish mV, and drops into the 100's
B1S1 reads 1.6-7.2% LTFT's, it bounces around
B1S1 reads dead @ 25.0% and NEVER moves
well, I have been getting low voltages DTC's for Bank 2 sensor 1
B1S1 reads around 700ish mV, and dips down some
B2s1 reads around 300ish mV, and drops into the 100's
B1S1 reads 1.6-7.2% LTFT's, it bounces around
B1S1 reads dead @ 25.0% and NEVER moves
Last edited by SmokinHot98; 10-09-2011 at 04:02 AM.
10-09-2011, 11:47 AM
#15
I logged on HPT, I reset the fuel trims and went for a drive from a cold start and the o2 runs good up until it heats up than flatlines. Its gotta be in the wiring or something. I'm gonna try to trace the heater wire and see if it was pinched somewhere. Don't know what else to do
10-09-2011, 12:31 PM
#16
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you need to ohm out all the wires going from the O2 sensor to the PCM. It never hurts to check all your grounds and make sure they are clean and you have low resistance.
Also your O2s should bounce up and down fairly fast when you look at your graph.
The heater lead on the O2 connector should have voltage to it anytime the ignition is at the ON position.
Also your O2s should bounce up and down fairly fast when you look at your graph.
The heater lead on the O2 connector should have voltage to it anytime the ignition is at the ON position.
10-09-2011, 12:52 PM
#17
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My bad on the tr5s I was thinking about that wrong.
Wouldn't be the first bad new o2 sensor I've seen.... Why did you change them??? And I wouldnt spend a whole lot of time hunting for wiring issues unless both o2 sensors (new and old) were doing the same thing. The heater should be irrelevant after it's warmed up, all it does is heat the sensors up faster and get them reading sooner (was implied for emmissions reasons, for cleaner burn sooner) your flatlining sounds like a bad o2 sensor just sticking. Ive seen some stick lean or fluctuate very little (still lean) and the PCM start jacking fuel trims wayyyyy up on one bank like bad enough to blow black suit at idle and ruin a cat in a hurry....
I'd put the old sensors back in, clear the codes, and see if it happens again the same way. Maybe you just got trigger happy and started trying to fix a problem with your truck that was just bad gas still in the system.
If this happens again I'd pull the fuel line off the rail run a hose to a bucket and jumper the fuel pump relay to drain the tank. Don't run it 100% dry or you'll likely burn the pump up. Fuel filter wouldn't be a terrible idea if you think the crappy gas is what started this...
Hope this helps
Wouldn't be the first bad new o2 sensor I've seen.... Why did you change them??? And I wouldnt spend a whole lot of time hunting for wiring issues unless both o2 sensors (new and old) were doing the same thing. The heater should be irrelevant after it's warmed up, all it does is heat the sensors up faster and get them reading sooner (was implied for emmissions reasons, for cleaner burn sooner) your flatlining sounds like a bad o2 sensor just sticking. Ive seen some stick lean or fluctuate very little (still lean) and the PCM start jacking fuel trims wayyyyy up on one bank like bad enough to blow black suit at idle and ruin a cat in a hurry....
I'd put the old sensors back in, clear the codes, and see if it happens again the same way. Maybe you just got trigger happy and started trying to fix a problem with your truck that was just bad gas still in the system.
If this happens again I'd pull the fuel line off the rail run a hose to a bucket and jumper the fuel pump relay to drain the tank. Don't run it 100% dry or you'll likely burn the pump up. Fuel filter wouldn't be a terrible idea if you think the crappy gas is what started this...
Hope this helps
Last edited by TTownTech; 10-09-2011 at 12:57 PM. Reason: Typo
10-09-2011, 01:07 PM
#18
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If you reallllllly want to check the wiring, unhook the PCM connector and the o2 sensor the put battery power on one wire, and battery ground on another and light a headlight bulb on the other end, GM TAC will tell you to do this to verify you don't have a weak wire a single strand would ohm just fine but would not light a headlight for long lol..
10-31-2011, 07:09 AM
#20
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Lol that's works, well just go ahead and send ever piece of your truck that didn't come stock, and I'll put it mine just to verify it's not PCM/harness related lol 