401code and PHH defeated! but... (1 Viewer)

Joined
Nov 23, 2011
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Let me begin by saying THANKS! to everyone who has taken the time to document and photo the processes for heater hose replacement and CEL codes eradication. I'm persistent, but my wrenchin skills woulda left me broke down, had it not been for the wealth of knowledge here on mud. The fsm was helpful, but the pics and write ups by mud members made all the difference.

I spent an entire weekend working on fixing these two issues (I know, I'm slow) had some good laughs, and learned a few things along the way. The pics on Slee, were the biggest help with the PHH. By the way, those firewall hoses were an ass whip, and they don't even get a name?! For the PHH, I chose to remove the hard pipe connected to it. After struggling with trying to get the new hose slid onto both ends for about an hour, I knew removing it was the only way to get out of the deal with some sanity. Once I did that, 15 mins to finish.

As far as the EGR system, I didn't test any of the old components. I didn't replace every component though, only the most common failures. Every single vac line was replaced, and all pass thru lines for coolant (thru TB). Fingers crossed, I turned the key and it fired up, no codes. Man, I was stoked!

I had driven about 110mi. when the CEL returned, however. This time indicating 130 and 133 for the O2 sensors. Relieved that it wasn't 401, bummed that I'm still chasing little gremlins. But the kicker is, this afternoon, just before shutting the truck down, I heard a fast clicking (like a relay, definitely electrical) coming from under the dash, left of the steering wheel, above the dead pedal. The sun was bright and I could be mistaken, but I thought I saw tiny sparks coming from the wiring harness! where the computer brain lives. It was erratic and fast, and eventually quit after turning the key off / on a few times and then finally driving away (had to get my kiddo home). Everything seems to work just fine, and there was no smell of even the slightest burnt wire when it happened, but I'm freakin out now. WTH!

Could the CEL codes be linked to this issue? I suppose. What would be the most logical place to start with figuring out what the hell the issue might be with the wiring? A quick visual inspection revealed no obvious wire damage. Is there a simple way to check the wiring for a short? Is the ECU failing?!

I appreciate any help!
Bart
 
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That's where your inside fuse panel is, have you checked all the fuses?


...Misspelled via IH8MUD app
 
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As you know, the ECU is a computer. It will either work, or not work. The wiring on the other hand, that goes to it can short sometimes and work fine others. While you were changing out the EGR parts, you had to push around the wire harness that passes right by the EGR pipe. All those wires in the engine bay, including the O2 sensors, pass by that very hot pipe. As you may already know, that wiring harness right there is a common problem in that the wires sometimes can get so hot that the insulation breaks down. Then, wires can short together, or break. Because you were working in that area, maybe this occurred. You can check by unwrapping the wire bundle and looking for melted stuff. Most usually re-wrap the harness with new heat reflective tape, because the old stuff breaks down over time. I got a roll from Jegs or Summit racing. I ended up with enough left over to also wrap up the cold A/C tube in the engine compartment.

If you have a friend with a real time scanner, the BEST thing to do is watch the O2 sensor output. If not, I would first try disconnecting the battery to erase the codes, then drive it again to confirm. It is a 2 trip code so, you will have to drive it twice before the light will set.
 
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Joined
Nov 23, 2011
Messages
68
Thank you for the reply. Now that I think about it, I do recall a couple of the old plastic harness straps (brittle as hell) just crumbling off that wire bundle. Crap, what have I gotten myself into.

On yours, were you able to unwrap that bundle all the way back to the firewall without removing anything else?

Thanks!


As you know, the ECU is a computer. It will either work, or not work. The wiring on the other hand, that goes to it can short sometimes and work fine others. While you were changing out the EGR parts, you had to push around the wire harness that passes right by the EGR pipe. All those wires in the engine bay, including the O2 sensors, pass by that very hot pipe. As you may already know, that wiring harness right there is a common problem in that the wires sometimes can get so hot that the insulation breaks down. Then, wires can short together, or break. Because you were working in that area, maybe this occurred. You can check by unwrapping the wire bundle and looking for melted stuff. Most usually re-wrap the harness with new heat reflective tape, because the old stuff breaks down over time. I got a roll from Jegs or Summit racing. I ended up with enough left over to also wrap up the cold A/C tube in the engine compartment.

If you have a friend with a real time scanner, the BEST thing to do is watch the O2 sensor output. If not, I would first try disconnecting the battery to erase the codes, then drive it again to confirm. It is a 2 trip code so, you will have to drive it twice before the light will set.
 
Joined
Apr 5, 2006
Messages
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Canyon Lake, TX
I had the intake off when I did mine, so I don't know how difficult it is to do with nothing taken off. I know many people here have been able to unwrap it without taking anything off so it shouldn't be too tough. But, I haven't done it.
 

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