P0174 P0151 Voltage Loss at B2S1 Connector off Harness

funghoul

funghoul

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Joined
Feb 3, 2024
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Tahlequah, OK
Hey there. I have had my 02 TJ since Feb of 23. I am currently looking for help or tips to track down a short or loose ground in my wiring harness. I have trouble codes P0174 and P0151. I have tested the voltage at the connector for B2S1. Sometimes it measures the correct voltage, but drops out inconsistently. I know it isn't the sensor because of the improper voltage readings at the connector.

I have gone through the factory service manual to check ground and splice locations for issues. The grounds I checked seemed fine. To be honest I just have little experience in tracking down faulty wiring.

I did have an issue previously where my blinkers stopped working due to a short in the trailer wiring harness from the back gate's movement. I rewired the damaged/corroded area. Not sure if the shorts could be related, but I do not have any issues with my blinkers now. Any help is appreciated, TIA!
 
I would recommend you check the 32 pin ECU harness connectors pins and clips for oxidation.
Verify the section of ECU wiring harness that is routed along the firewall behind the valve cover and has been known to rub against the threaded head stud in the right back corner of the head. The proximity of the harness has been known to rub thru the split wire loom and wiring insulation causing an intermittent short or break in voltage thru the wiring.
 
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Thanks! I'll definitely check that out. I was thinking it could be a contender. I think I might go ahead and give the grounds a good clean as well. There was quite a bit of dirt and grime down there.
 
Got a chance to check it out really good today. The section of ECU harness you mentioned has rubbed significantly against the threaded stud. The "conduit" like material protecting the harness is rotted/crumbly. I'm going to inspect this area out a bit closer to really look for wire damage. I also removed the long plastic cover that protects the wiring along the fuel rail to inspect, everything looks good in that area. However, I threw another code P0205. Relates to the injectors. Noticed the pin for the green/yellow stripe wire had backed out of the connector for injector #5. Reseated the pin and reconnected it. The green/yellow stripe wire for injector #4 looks a bit chewed also.

Moving forward, what are the best options to fix these issues when I track down the specific problem locations? I'd really like to avoid splicing into the harness, as I'm sure that will do nothing but cause more headaches later down the line.
 
The repair depends upon how bad the wiring is chewed up or worn thru near the threaded head stud.
However you decide to repair the wiring will depend upon how bad the damage is and what you have available to repair that damage. Just make sure the strands of the individual wires do not touch each other.
After I inspected my wiring near the threaded head stud; I installed a rubber spark plug boot onto the stud to ensure there is no harness contact.
 
CharlesHS said:
The repair depends upon how bad the wiring is chewed up or worn thru near the threaded head stud.
However you decide to repair the wiring will depend upon how bad the damage is and what you have available to repair that damage. Just make sure the strands of the individual wires do not touch each other.
After I inspected my wiring near the threaded head stud; I installed a rubber spark plug boot onto the stud to ensure there is no harness contact.
Click to expand...

Okay. Sounds very manageable. The injector wire is not super chewed, so I'll give it a good wrap with electrical tape to prevent further issues there.

My biggest issue is having to stand upside down on top of my head in the engine bay to get a good look at the section of harness near the stud haha. It's a tight fit with little stretch. I'm sure I'm not the first nor the last to have that issue. Hopefully, I'll find my problem area soon. Thanks for your help!
 
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