Is this a reasonable plan – Nissan Titan ABS problem.

Sorry – this is kind of long.

2004 Nissan Titan. Tailpipe broken off about 1ft past the muffler where there was a flange. Didn’t think it would hurt anything, but the exhaust has melted the wiring harness which is sorta close by. Quick web search shows I’m not the only one to have this happen.

Only issue was no signal from right rear wheel sensor. My mechanic soldered in a new connector on the harness to replace the original which was melted and replaced the wheel sensor b/c the pigtail seemed melted. But that hasn’t fixed the problem. He didn’t have time to investigate further and I took the truck back (ABS and traction control is inop). I looked things over and while the plastic loom is definitely very melted, it kind of appears to me that the individual wires are intact, but their insulation is just kind of stuck together now.

This is an active sensor with a power wire and a signal wire. The working left rear sensor power wire shows 11.2V, and the RR (problem) sensor reads .35V. I pulled the pwr and signal wire out of the melted bundle to try to make sure they weren’t shorting there, and that did not fix anything.
I am thinking I will cut the right rear pwr wire ahead of the melted section and see if it has correct voltage with the melted section out of the equation.. If it does have voltage, then I could splice a new wire past the melted section and see if the sensor works. If there’s still no voltage, then it seems like the ABS computer is no longer providing power to that sensor.

I am trying to make sure the ABS control module is or isn’t the problem. It’s an $800 part, so I don’t want to replace it unless I have to, and I don’t want to damage a new one if the harness was what killed the original one.

Is this a reasonable plan to troubleshoot?

Thanks… (and I am kicking myself for ignoring it when the tailpipe broke off months ago).

Seems like a quick cut and splice of the melted wiring/loom is the right move.

Is there a inline plug between the ABS module and the damaged area? If so I would try unplugging it and see if you have the correct voltage, then you know where to start.

Dumb question, but did you check the ABS fuse(s)? Who knows what wizardy lies within the ABS module. It may need a reset with the appropriate factory scan tool.

I think you're on the right track testing the power output upstream from the damage.

In reply to Donebrokeit:

Good call on the additional connector upstream. I found a site with the full service manual posted, and that led me to the SMJ or "Super Multiple Junction" connector (gotta love Japanese nomenclature ). Was able to verify supply power there for the bad sensor. So that pointed away from the ABS ECU being bad.

After splicing in 2 new wires further up the harness (fully past the melted section) and verified supply voltage - no joy, still no sensor reading. Oh, they look like twisted pair - so redid my splice with a similar twist - nothing. But my mechanic had shown me the old sensor so I could see how melted it was, and I had kept it. Put that back in and boom sensor reading again at the ECU. So seems like the new sensor was bad and the old one though melted, is still good. That's the good news.

The bad news is that now I have a new brake pressure sensor fault code and some engine CAN bus error fault codes. Reset them, but they came back.

Theory one is that when I extricated the sensor wires from the melted harness for splicing, some other wires may have gotten together and are shorted or broken.

Theory two is a weak battery. Didn't mention it yesterday, but after having the key in the ON position for 2-3 hours, the battery was dead - would barely roll up the windows and read about 11.3V, would not crank. I charged it for a few hours last night and it seemed to function ok today, but is reading about 12.3V.

So, still more to do, but I am heading out of town now (in another vehicle), so won't be able to look at it for a couple of days.

So, just to follow up on this since I hate when people neglect to post the final resolution to a problem they are chasing...

I got a new battery since the existing one was over 4 yrs old and acting weak, and I had seen dashlight freakout in the past with a bad battery.  Was pretty stoked when I installed the new battery and had no warning lights on the drive home from Autozone... but the ABS and SLIP lights came back on the next day.

Only one code after new battery - for brake pressure sensor.  I cleaned the terminals for the 2 sensors but no change.  Ordered up new ones, which just got here today, and looks to have fixed the problem.  Nissan forum said fairly common issue.

So, summary - broken exhaust caused melted wires, which caused loss of pwr feed to wheel sensor, new wheel sensor was bad, old one still worked - wire issue was actually in the melted main harness.  Weak battery appears to have caused the CAN bus errors (I guess, b/c they went away with new battery and there are no CAN bus signals passing through the rear harness that melted), and pressure sensor decided to go bad in the middle of all this.  

That was rather painful - and partially self inflicted, b/c I should have just gotten the tailpipe fixed right away