SOLVED: Code 26 with power cutting out

bpenn1980

SILVER Star
Joined
Nov 15, 2007
Messages
1,109
Location
Los Angeles
Solved: Moisture in TPS

Hi all,

I did some searching and leg work on this today without success, so a quick post to see if anyone has thoughts while I keep working the problem.

Background: Recently completed ~1,000 mile trip into Mexico. Solid CEL on last few hundred miles back into US with maybe slightly rough idle, but no drivability issues. Pulled codes 26 and 71 today. I don't think 71 is my primary concern right now.

I planned to fill up with "clean" premium chevron today and run a tank to see if my codes resolved. I wont get that opportunity since on my drive back home from the gas station (filled with new premium) I had the issue shown in the video below which kills the drivability of the truck. See video, but basically anytime I put too much load on the engine (moving or parked), the RPM will cut out and ramp back up, cut out, ramp back up, etc

New video by Brad Pennington - https://photos.app.goo.gl/S8rPRchfCX3o3BicA - from drive when I first noticed it happening coming back from gas station
New video by Brad Pennington - https://photos.app.goo.gl/qHCKWVynZoomE3AN9 - from driveway after the engine cooled a little (seems to idle fine on start up, but after inducing the problem, the idle goes to sh!t)

I got back home, unplugged O2 sensors. Resistance was in spec, though sensors are from ~2007. Outer sensor had a little corrosion on one pin, but not bad. I unplugged the ECT (engine coolant temp) sensor and got resistance readings from the sensor that seemed in line with the FSM based on how hot the intake/block felt.

That is where I left things today.

I did a fair amount of work in advance of the trip and things were running very smoothly until we returned home. We did get into fair amount of water, mud, sand, salt exposure during the trip, so I was hoping the O2 sensors were soggy, but no such luck.

Thanks for chiming in if you have any ideas.
 
Last edited:

bpenn1980

SILVER Star
Joined
Nov 15, 2007
Messages
1,109
Location
Los Angeles
Ok, got it!

Basically what I think happened was that we got back from baja, I parked the truck, washed it, sprayed down the engine compartment, then let it sit overnight. I got in the next day and had the issue with the engine not revving over 2200 rpm. Though I spray the engine down after trips regularly without issue, I'm pretty certain that this time the TPS connector got moisture in it.

Anyway, I ended up replacing the Engine Coolant Temp sensor because it was relatively cheap and in order to do a proper sensor test I'd have to remove it anyway. Wasn't the issue. I unplugged both O2 sensors which did not fix the issue. However, both o2 sensors were 14 years old (almost to the day! and yeah, that antiseize worked a treat as well)
1641712508931.png


Replaced both o2 sensors with Denso 234-4520 x2. Wasn't the issue. I tested AFM, IAC, TPS, and fuel pump relay. All tested in spec. Well, actually the fuel pump relay tested 83ohm on one of the measurements when it was supposed to have continuity, but I called it good enough. Not the issue.

What I think fixed it, in addition to a week having gone by which allowed everything to dry, was blowing the TPS connector out with compressed air, then used some electronics anti-corrosion spray and dielectric grease to seal it up. I did the same for the AFM and IAC connectors for good measure. Truck revs beautifully again!

I still need to do a couple trips on the highway to see if my 26 and 71 code are still there, but at least the truck is very driveable again.

Hope this helps someone in the future.

PS- I got lucky that code 26 pointed me to ECT (amongst other items) because apparently a failed ECT can present some similar symptoms, which then ultimately put me on the mud research path to TPS.

Solved - Help needed - Won't Rev Past 2200RPM - https://forum.ih8mud.com/threads/solved-help-needed-wont-rev-past-2200rpm.891316/ -Tools for the win AGAIN :beer:
 

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