Multiple codes, even after repairs... Background and questions

[MoonLyght]

Hey, Everyone.. Hope the Holiday was good to you and yours... I've got a 2004 3.7l 4x4...bought the Penguin about 4 months ago. Within a few days, 02 sensor code popped up, and then went off within a couple of days... Then came back on, followed by 7 other codes. I researched all the codes as much as possible, and started with the mass flow sensor, and the little filter (which was disintegrating) inside the air box, to the right. All codes went away... Until the O2 came back.

I replaced the 02 (OBDll kept saying that was the first line of repair), and code went away for a couple of days, and then... Yup... It came back. But different sensor and bank. Now it sort of bounces around between the banks and sensors...

So far, I've replaced all 4 of the O2 sensors, mass flow sensor, mass flow filter, pcv valve and hose, plugs, ECT, thermostat, fan assembly (went out a few weeks ago), water pump, and serpentine... Coming back from a trip out on Hwy1 this past week, I suddenly realized that the engine/****** sounded to "high"... Similar to having turned off the OD (which I hadn't re flat ground)... Although not officially in "limp" mode, I stayed under 40mph to get out of the Altimont Pass (California), to get to some place where I could easily get help. Got towed back home, and now I get the P0176, P0700 and P1776.

Reading up on the P1776, my initial thought was correct, as it sounds like it's stuck in second gear... The other things that she's always done is, stick when shifted... Like shift isn't going all the way (key gets stuck on ignition sometimes, and I have to give an extra nudge into park, but goes slightly past drive sometimes and has to be nudged forward)... Other thing is that if I'm coasting in traffic, and give her a little gas, there's a clunk... but only only when the check engine light is on...sometimes louder/harder than "normal"... But engine wise, and cruising down the road, she's totally smooth... Highway, I'm getting around 21mph, and able 18 in the city!

I actually have the TCM/PCM on my list for possible replacement... The shop I take vehicles to, when I can't do something myself, or my SIL isn't available, said the PCM could be shooting out false codes, particularly as they are so random, and can disappear as fast... Anyone else have this issue??? Resolution if you did? Is it "smart" to just replace the TCM, and is this just a piece of the PCM itself, or are they two separate, but connected pieces (when I look up the TCM, it always gives me the PCM)? Any help is appreciated! Loving my Penguin, and looking to trick her out a bit for some adventuring, but can't figure this out... TIA! p

 

[DadOSix]

You sure have alot going on there.

First thing I think of when getting all these semi-related codes is bad grounds and air (vacuum) leaks.

That 3.7 should have a pair of ground straps off the firewall with 1 strap to each head.

Also ground strap down low on the right front of the frame rail.

These jeeps are notorious for electrical gremlins. They are old and things do corrode. A youtube mechanic i follow calls the corrosion ‘the green crusties”

When you are doing replacement of electrical parts, try to stay oem (mopar) as much as possible. The consensus here on jeepkj is that it saves time and headache in the long run.

Your o2 sensors should be ngk.

Finally, the air / vacuum leaks come from brittle hoses, etc. when you have lean codes and 02 codes, it is wise to run the whole length of the intake and vacuum system. I found a rotted elbow on my 04 that looked great from the top, but was holey underneath.

Does your scanner let you look at short and long term fuel trim data? That can help decide IF an 02 sensor is bad.

So - my advice in a nutshell : diagnose. I will devote a decent chuck of time and brain power before swapping something just to see. It gets expensive throwing parts without being sure.

 

[MoonLyght]

You sure have alot going on there.

First thing I think of when getting all these semi-related codes is bad grounds and air (vacuum) leaks.

That 3.7 should have a pair of ground straps off the firewall with 1 strap to each head.

Also ground strap down low on the right front of the frame rail.

These jeeps are notorious for electrical gremlins. They are old and things do corrode. A youtube mechanic i follow calls the corrosion ‘the green crusties”

When you are doing replacement of electrical parts, try to stay oem (mopar) as much as possible. The consensus here on jeepkj is that it saves time and headache in the long run.

Your o2 sensors should be ngk.

Finally, the air / vacuum leaks come from brittle hoses, etc. when you have lean codes and 02 codes, it is wise to run the whole length of the intake and vacuum system. I found a rotted elbow on my 04 that looked great from the top, but was holey underneath.

Does your scanner let you look at short and long term fuel trim data? That can help decide IF an 02 sensor is bad.

So - my advice in a nutshell : diagnose. I will devote a decent chuck of time and brain power before swapping something just to see. It gets expensive throwing parts without being sure.

Thanx, DadOSix... I can def run down the ground straps... As well as checking out the hoses... O2s are not ngk, although the plugs are... Wonder if they'll exchange them??? It's I only been like 1.5 weeks. Any thoughts on the transmission? Is this something I can just reset, ie disconnect the battery for computer to reset, or something like that?? Not climbing any hills for a few weeks, but could def use it around town vs my old corolla... But also don't want to jack up the transmission!

 

[DadOSix]

No theory on the p1776 code as of yet.

Remember that there is 1 or 2 harnesses that plug into the transmission.

I’d be looking hard at all those. The wires might be corroded at the plug.

This is sort of like a game of clue or whodunit.

What appears as a bad solenoid valve might be related to all the other stuff we are seeing.

There is nothing ‘simple’ when computers are involved in a vehicle control system.

A lot of ‘possible’ issues. Could be the solenoid pack, could be the wiring, could be the tcm,

I am not strong in transmission diagnosis tbh, but maybe someone who is will jump in to guide us thru.

 

[MoonLyght]

So... I ended up just disconnecting the battery for a day+... My thought being, it would clear codes, so maybe it would clear what was hitching in the ******... If nothing else, might give me a better idea whether it's the ****** itself, or a sensor/module of some type. It unlocked the ******, which is great! And then someone I was talking to said I should check out the "TCCM"... transfer case something or other... Not finding much on this... Any thoughts, or videos to recommend? Is this something I can do myself? I can follow a lot of videos, but can't take out a ****** ... TYIA