The thing that has really driven this home for me this week is that it took 20 years to spend $2 trillion for the war in Afghanistan. Now we are passing multiple trillion dollar stimulus packages like it’s as simple as putting money in a birthday card.
Jeep LS swap for the LJ
- Thread starter glockman
- Start date
anderson750
I'm working on it Rose
- Location
- Price, Utah
It is that easy for politicians
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
I've been having an intermittent bank 2 lean condition. The jeep falls flat on its face out of nowhere. Logging it, bank 2 O2 sensor drops to 0-50mv. I swapped sensors side to side and it stayed bank 2. I dug into the harness and found the low sense wire had a rub through the insulation 
Fixed this and it went away for a couple hundred miles but came back, still intermittent. I didn't want to dig into the harness again so I ran new sense high and low wires from the O2 sensor directly to the PCM. Still getting low voltage intermittently. It will jump to 450mv at startup and then start toggling correctly (100-900mv) after it warms up and is in closed loop. You can drive it for 30 miles before it will intermittently drop to 0 volts for a 2-30 seconds and nearly kill the jeep, then it starts functioning properly for another 5, 10 or 30 miles.
It can't be the sensor or sensor wiring as the wires are new and the sensor swapped. I thought it might be a stuck injector so I swapped them bank to bank. No change.
I suspected the injector harness since all the +12 wires get tied together for a stand alone harness. I pulled that apart last night and remembered I had intentionally put half of the bank 1 injector + wires with half of the bank 2 wires so intermittent power to injectors dropping would affect both banks.
I had totally overlooked an exhaust leak but doubt that is the cause due to the intermittent nature. I'm also assuming any vacuum leak would affect both banks. I'm stumped.
Fixed this and it went away for a couple hundred miles but came back, still intermittent. I didn't want to dig into the harness again so I ran new sense high and low wires from the O2 sensor directly to the PCM. Still getting low voltage intermittently. It will jump to 450mv at startup and then start toggling correctly (100-900mv) after it warms up and is in closed loop. You can drive it for 30 miles before it will intermittently drop to 0 volts for a 2-30 seconds and nearly kill the jeep, then it starts functioning properly for another 5, 10 or 30 miles.
It can't be the sensor or sensor wiring as the wires are new and the sensor swapped. I thought it might be a stuck injector so I swapped them bank to bank. No change.
I suspected the injector harness since all the +12 wires get tied together for a stand alone harness. I pulled that apart last night and remembered I had intentionally put half of the bank 1 injector + wires with half of the bank 2 wires so intermittent power to injectors dropping would affect both banks.
I had totally overlooked an exhaust leak but doubt that is the cause due to the intermittent nature. I'm also assuming any vacuum leak would affect both banks. I'm stumped.
UNSTUCK
But stuck more often.
The wire repair has me scratching my head. You made the repair and it went away for a few hundred miles? Did it ever last that long with the bad wire still in place? When you ran the two new wires, how did you install them? Crimped and soldered new terminal ends and then inserted them into the harness connectors? Cut the original wires outside the harness connectors and attached new wires to the original wires?
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
It ran 80 ish miles after I repaired the oem wire without issues. Symptoms are identical pre and post which makes me think the original wire rub wasn't the issue but maybe I moved something the right way when I repaired it.
For the repair, took two new wires, sheathed them, crimped new pins on the pcm side and soldered them to the o2 plug pins after removing the original harness wires. Then stuck them back into the original harness plug. So pin to pin new, crimped and soldered. O2 went to 0vdc a block from the house. I let it sit a week and drove it to work for 3 days without an issue. Friday it stumbled (0vdc) twice on the 7 mile commute home and once in a mile to running to the store and back.
I'm convinced it's something in the harness but I can't figure out what else would only affect one bank. Grounds for the injectors come through the pcm and they are all 8 in one plug.
UNSTUCK
But stuck more often.
How are you measuring your voltage? Freeze frame? If so, does the freeze frame show your 5v input to the sensor and 0v back to the PCM, or just 0v at the PCM?
Can you duplicate this issue in your garage? Plug your DVOM to the reverence side right at the O2 and make sure you always have that 5v there. Then switch over to the return wire right at the O2 and see if you drop to 0v there when it stumbles.
I guess you could rig some extra wire to the input/output of the O2 so you could put your meter in the jeep and watch what happens while you're driving, when it stumbles. Compare those numbers to what your freeze frame shows.
My suspicion is the PCM is randomly dropping the 5v reference. So if you get 0 volts in you'll get 0 volts out. This all gets thrown out the window if the PCM sends the same 5v to each O2.
Can you duplicate this issue in your garage? Plug your DVOM to the reverence side right at the O2 and make sure you always have that 5v there. Then switch over to the return wire right at the O2 and see if you drop to 0v there when it stumbles.
I guess you could rig some extra wire to the input/output of the O2 so you could put your meter in the jeep and watch what happens while you're driving, when it stumbles. Compare those numbers to what your freeze frame shows.
My suspicion is the PCM is randomly dropping the 5v reference. So if you get 0 volts in you'll get 0 volts out. This all gets thrown out the window if the PCM sends the same 5v to each O2.
DaveB
Long Jeep Fan
- Location
- Holladay, Utah
I like to measure O2 sensors with my oscilloscope since the output is basically a square wave of varying period. I have several scopes if you want to borrow one. You could measure the 5V at the computer and at the sensor and see if the error is the same at both ends of the wire.
RockChucker
Well-Known Member
- Location
- Highland
Is your harness/ecm red/green or red/blue connectors? Not sure how well it would work…But I have a green/blue ecm tuned for a 5.3 and a 4l80. I don’t know that you’d be able to drive, but it should run the motor to see if the issue goes away. Assuming you can reproduce the issue at idle.
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
I can't reproduce it predictably. I've used hp tuners and torque to log the voltage read by the pcm when it stumbles. In the garage at idle I could not get it to clear at one point, pulled both o2's and they both read 0.5vdc at the harness sense high without the sensor plugged in. The low side of the harness had continuity with ground and no continuity to the sense high.
@UNSTUCK i think you are correct, it is likely dropping voltage to the sensor. The postive voltage is supplied separately to each sensor so it would only affect one bank if it dropped. I think I've eliminated all the O2 sensor wires so it would likely be the pcm dropping the signal.
I tore the harness apart checking the injector power wires this week and I just loosely wrapped it all back up and drove 50 miles today Datalogging with hp tuners. No stumble, lol.
I'm going to continue driving and logging it to see if there is a map, maf or st/lt fuel trim issue that correlates. I haven't ruled out a vacuum leak on the intake or an exhaust manifold leak. The fuel trims should help me rule out vaccum. I've floored it a couple times and got the stumble to clear, which might mean a vacuum leak, just odd that it would be intermittent.
Thanks for the offers Dave's 😁, I might take you up on them if I rule out the mechanical stuff. I have access to an oscope but the pcm would be a great troubleshooting tool.
@UNSTUCK i think you are correct, it is likely dropping voltage to the sensor. The postive voltage is supplied separately to each sensor so it would only affect one bank if it dropped. I think I've eliminated all the O2 sensor wires so it would likely be the pcm dropping the signal.
I tore the harness apart checking the injector power wires this week and I just loosely wrapped it all back up and drove 50 miles today Datalogging with hp tuners. No stumble, lol.
I'm going to continue driving and logging it to see if there is a map, maf or st/lt fuel trim issue that correlates. I haven't ruled out a vacuum leak on the intake or an exhaust manifold leak. The fuel trims should help me rule out vaccum. I've floored it a couple times and got the stumble to clear, which might mean a vacuum leak, just odd that it would be intermittent.
Thanks for the offers Dave's 😁, I might take you up on them if I rule out the mechanical stuff. I have access to an oscope but the pcm would be a great troubleshooting tool.
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DAA
Well-Known Member
- Location
- West Bountiful, UT
I have a smoke maker if you want an easy way to check for tiny vacuum leaks.
- DAA
- DAA
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
I have a kid that drives a Cummins and wears square toe'd boots. So I'm wondering if his Vape will actually serve a purpose beside making me feel like a failure as a father. 
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
Had an epiphany last night. I have downstream O2 sensors and "free flowing" cats. This morning on my commute, I logged the downstream O2 on bank 2. It was reading 0.3 volts average during the one 0v event I had. So it definitely isn't a mechanical issue. It's dropping voltage on the upstream O2. Now I just have to determine why, PCM or wiring.
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
I am going to try repining the harness so bank 2 sensor 2 is in the bank 2 sensor 1 slots in the PCM plug. If that fixes the issue, I'll move the actual sensor to the upstream location. Quick and easy fix.
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
Uh, I would never modify a vehicle to not monitor all emissions equipment. Just swapping stuff for test purposes, off road use only on a closed course with a professional driver.
. Just swapping stuff for test purposes, off road use only on a closed course with a professional driver.In MexicoUh, I would never modify a vehicle to not monitor all emissions equipment
glockman
I hate Jeep trucks
- Location
- Pleasant Grove
Just an update. The O2 swap didn't fix the issue so the O2's appeared to be a symptom rather than a cause. I did some more troubleshooting and found there was a short somewhere in the harness. There was continuity between the positive and negative battery terminals. I tried pulling some fuses to isolate the circuit but got no where.
At this point I punted and ordered a new stand alone harness from Wayne Hartwig at 150tunes. That was back in November, lead times being what they are these days, it arrived last week and I got it installed this week.
I have to say, buying a harness is so much easier. While installing it, I kept thinking, where is xyz circuit, then I realized it is all included in the harness. Were I to do this again, I feel like it's money well spent. I got the old harness out and the new one wired in about a day. The only issue I have is it's no where as clean as my custom harness, obviously. You get a one size fits all harness length, but I was able to route everything without too much coiling and snaking. Overall, it's a good compromise.
I put 30 miles on it yesterday with zero issues. It also starts without the double crank I was having to do prior. Not sure what fixed that but I assume there was some sequencing with the ignition that I had wrong by tapping the wrong place in the power up sequence.
Good to be driving this again, hopefully it lasts longer than a month before another issue pops up.
At this point I punted and ordered a new stand alone harness from Wayne Hartwig at 150tunes. That was back in November, lead times being what they are these days, it arrived last week and I got it installed this week.
I have to say, buying a harness is so much easier. While installing it, I kept thinking, where is xyz circuit, then I realized it is all included in the harness. Were I to do this again, I feel like it's money well spent. I got the old harness out and the new one wired in about a day. The only issue I have is it's no where as clean as my custom harness, obviously. You get a one size fits all harness length, but I was able to route everything without too much coiling and snaking. Overall, it's a good compromise.
I put 30 miles on it yesterday with zero issues. It also starts without the double crank I was having to do prior. Not sure what fixed that but I assume there was some sequencing with the ignition that I had wrong by tapping the wrong place in the power up sequence.
Good to be driving this again, hopefully it lasts longer than a month before another issue pops up.