[Redtruck-VA]

I believe you are spot on, except the front sensors generate the oxygen signal for the pcm to respond to. The rears count "flips" which is a shift in voltage being one flip. The fronts also count voltage shifts. When the front and rear flip count are the same or close to being the same a code is set because the cats are nolonger functioning. This is why you can remove (isolate) the rear(s) sensors so they cannot count the same as the front and you won't have codes. Unfortunately the pcm is smart enough to know when the rear sensors are simply unplugged as you will get a code for "high voltage". This follows through for all sensors, if you have a "high voltage" code it means either the sensor is unplugged or a open circuit. It's easy to get confused, the manuals are not clear on a lot of sensor functions.

 

[DodgeGuy524]

Alright. More data has come in. haha.

First off, thanks to everyone for brainstorming. This is the best help I've received on a forum in a long time.

So tonight I installed brand new NTK front O2 sensors and then reset the PCM. The O2 sensors were both in the correct position upstream. I could literally read the harness tags that said "LF" and "RF". Pulled the fuse (#23) and then got in the truck, put on my seatbelt and turned the key on. Got the 3 consecutive chimes and then waited 30 seconds for good measure. Turned truck off, put fuse back in, checked for DTC's. No codes, so life should be good.

Started the truck... same issue. haha. WOOHOO!!!

So I decided to drive the truck for about 30 miles of mixed style driving. up to about 65mph, some stop-and-go, and some idling as well. Still doesn't want to hold an idle in gear without the up-down-up-down surge and ultimately a stall.

Drove it all the way back home and tried to let it idle. It does the exact same thing that is in the original video.

So, round 2 is the next variable. I reset the PCM again, and then took it back to stock tune. No codes present... Give it a whirl.

Same issue.

I've also cleaned the IAT Sensor and MAP Sensor. Neither of which were very dirty since I replaced them about 30k miles ago.

Soooo.... now I'm really at a loss, guys. I crawled under the truck with a flashlight and wiggled and checked every plug I could see and some I couldn't. I checked the vacuum lines and couldn't see any signs they were ever disturbed let alone cracked or leaking. No visible leaks at the heads, and I don't think a leak after the upstream O2's would cause this even if there was a leak.

I'm almost ready to take it to the dealer and just pay them to run full diagnostic

 

[Redtruck-VA]

What are you using to clean the sensor and TB? Remove the TB plug and look at the pins to see if anything is bent. This has to be related to something the shop did if it ran ok to the shop.

 

[DodgeGuy524]

I use electrical contact cleaner on pretty much anything that has a circuit attached to it. It's not very aggressive, doesn't etch, and doesn't leave a residue. Plus it evaporates almost instantaneously.

I've used it for years and no issues.

For the TB, I use the same cleaner applied indirectly. Goes on a lint free rag then use the rag. The TB is never dirty enough to need the toothbrush.

I really don't know what the shop could have done. They didn't move the front O2's because they were in the headers when i arrived. They welded everything on the ground next to the truck. I watched them the whole time. Only thing they did was put my band clamps back on the collector to Y-pipe fitting and weld the cutout to the straight section that meets up with the muffler.

Do y'all think the dealer would even be of any help on this? I think I need someone with real diagnostic tools on this one. I am stumped

 

[MANual_puller]

I'm with Greg, it would be an odd coincidence if it was unrelated to the recent work done. It's happened before where something inadvertently happens without noticing. Anyone remember when Cristoff couldn't get his engine to fire after the trans swap? It wound up being a simple plug came undone, in his case the crank position sensor. You'll get it, it's likely something simple :thumb:

 

[charged392]

Your going to need a scanner for this one and someone with good knowledge that can watch what's going on as it runs. If you drove it to the shop then this happened something go messed up.

 

[Redtruck-VA]

Did the truck run normal to the shop with the headers installed? Are there any unprotected wires near the header pipes that could have been damaged? Did it start to surge immediately at startup at the shop after the work was done? Do a complete reset by removing the battery cable. And if still surging, try unplugging the front O2s and see if the surge changes. If the symptoms don't change with the sensors unplugged then it points at a problem with the sensors still. I still believe this is something simple.

 

[Hugh Jassole]

Definitely got the sensors on the right way. Everything was marked, and I've changed O2's on this truck a few times so I can identify the rear and the front just looking at them.

Didn't know about reference air through the wires. This is the one instance that apparently soldering ISN'T the best route. haha. The worst part is that the Pacesetter instructions actually recommend soldering the wires. All that said, I don't believe the rear O2's are the ones throwing the codes. I think it's the fronts. I say this because I only had to extend one of the rear O2's and I'm getting a rich reading on both banks. And I believe those error codes come from the front O2's.

I'm curious if cleaning the front O2's is possible. I'm wondering if the ceramic and other contaminants cooking off caused them to get coated in something and malfunction. I might just buy a couple new fronts. Do our trucks still not like Bosch sensors?

our trucks hate Bosch sensors. NTK is the oem maker, and Rockauto has them cheap. It may not matter on other makes, but it definitely matters on dodges. My Dakota R/T is the same way. NTKs or bust.

 

[Hugh Jassole]

Alright. More data has come in. haha.

First off, thanks to everyone for brainstorming. This is the best help I've received on a forum in a long time.

So tonight I installed brand new NTK front O2 sensors and then reset the PCM. The O2 sensors were both in the correct position upstream. I could literally read the harness tags that said "LF" and "RF". Pulled the fuse (#23) and then got in the truck, put on my seatbelt and turned the key on. Got the 3 consecutive chimes and then waited 30 seconds for good measure. Turned truck off, put fuse back in, checked for DTC's. No codes, so life should be good.

Started the truck... same issue. haha. WOOHOO!!!

So I decided to drive the truck for about 30 miles of mixed style driving. up to about 65mph, some stop-and-go, and some idling as well. Still doesn't want to hold an idle in gear without the up-down-up-down surge and ultimately a stall.

Drove it all the way back home and tried to let it idle. It does the exact same thing that is in the original video.

So, round 2 is the next variable. I reset the PCM again, and then took it back to stock tune. No codes present... Give it a whirl.

Same issue.

I've also cleaned the IAT Sensor and MAP Sensor. Neither of which were very dirty since I replaced them about 30k miles ago.

Soooo.... now I'm really at a loss, guys. I crawled under the truck with a flashlight and wiggled and checked every plug I could see and some I couldn't. I checked the vacuum lines and couldn't see any signs they were ever disturbed let alone cracked or leaking. No visible leaks at the heads, and I don't think a leak after the upstream O2's would cause this even if there was a leak.

I'm almost ready to take it to the dealer and just pay them to run full diagnostic

Have you had the battery load tested ? Just because it starts the truck doesn't mean it's good. Our trucks don't like to idle with a weak battery. Also, did they disconnect the battery before they started welding on things ? I've heard of instances where this has ruined the PCM or battery

 

[DodgeGuy524]

I could have the battery load tested, but it's only about 8 months old and it's a really stout battery. I highly doubt it's the battery.

It started having issues just before I got to the shop, so I don't think it's the shop's fault. I did get a good idle on initial startup with the headers and no Y pipe. I just wanted to check them out before I went through putting on the Y-pipe to see if I would need to re-do anything.

An update to the whole situation. I did some highway driving and I popped a DTC. Got a P0404 code. Which is weird because that EGR Valve is pretty new. It may still be under warranty, so I might just go get a new one and throw it in. Wouldn't that be awesome it that was the solution.

I also got a P2299, but that's because I have to hold the brake and the gas at the same time to keep it from stalling at a stop light. The PCM Doesn't like that so it throws the P2299.

There aren't really any loose wires or unprotected wires near the headers. I put heat shielding over the trans selector cable and the trans cooler lines. Neither of which was close enough that I was really worried about it, but it was worth doing it just in case. Only other sensors or wires even close are the crank position sensors. Doubt that's the problem either, And they are untouched and no risk of interference.

If you guys can brainstorm ANY other sensors that might be causing this, let me know and I'll trace them and replace them if I can.

 

[DodgeGuy524]

Well... Today is a great day. Drove the beast to work and it ran worse than any day before. Truly terrible commute. I stopped by O'Reily's on the way home to pick up a new EGR Valve and a PCV Valve (just in case). The EGR Valve was under warranty from the last time I replaced it.

Took the time to install it and clean everything around it while I was in there. Reset the PCM one last time... She purrs like a kitten!


THANK YOU ALL for the help and recommendations. I've been rebuilding cars since I was 12 with my dad and I'm in the middle of a full restoration right now, but this one had me stumped. I appreciate all of the recommendations and your help through the troubleshooting. And hopefully this can help someone out in the future.

 

[MANual_puller]

Well... Today is a great day. Drove the beast to work and it ran worse than any day before. Truly terrible commute. I stopped by O'Reily's on the way home to pick up a new EGR Valve and a PCV Valve (just in case). The EGR Valve was under warranty from the last time I replaced it.

Took the time to install it and clean everything around it while I was in there. Reset the PCM one last time... She purrs like a kitten!


THANK YOU ALL for the help and recommendations. I've been rebuilding cars since I was 12 with my dad and I'm in the middle of a full restoration right now, but this one had me stumped. I appreciate all of the recommendations and your help through the troubleshooting. And hopefully this can help someone out in the future.

GREAT NEWS! :thumb: It seems weird because it was new but these PCMs any more are smart enough that you've got to trust the codes :thumb:

 

[charged392]

Wow egr I thought we had that rules out but you never know glad it fixed

 

[Redtruck-VA]

This once again points out that there is a very high failure rate among new replacement parts.

 

[DodgeGuy524]

Totally agree. That's why I just sort of did it as a last ditch effort. Ahould have replaced all my lifetime wqrranty sensors up front.

On the plus side, my new PCV Valve is blue, so I think that adds like 43 horsepower.

 

[Redtruck-VA]

Only if your name is Petty....

 

[HemiFun05]

Totally agree. That's why I just sort of did it as a last ditch effort. Ahould have replaced all my lifetime wqrranty sensors up front.

On the plus side, my new PCV Valve is blue, so I think that adds like 43 horsepower.

----------------------------------------

:thumb: :dance:

 

[SUPER BEE]

My replacement was blue as well, think it made it run a little stronger. He, he,he.

 

[04sthemi]

Mine is blue as well. My egr is non existent so I won't have to worry about that, but glad you got it figured

 

[kcd1369]

Great job! :thumb::thumb: