05, 5.3 L59, I reworked my own harness, no rear O2 sensors, about 5K miles on it.
I'm getting an intermittent O2 sensor heater resistance code at startup, car runs fine though. Both banks throw a code at the same time. I'm not running an O2 sensor fuse.
As far as I know, the only thing they have in common is the switched power source and they're both wired independedntly into my switched pink wires.
I'm guessing an intermittent short or open circuit in the pink power wires would be the most probable cause. Anything else obvious I should consider?

 

ttt,
anyone have input, or did I figure out the obvious?

 

Do you have long tube headers on the car?

Jon
PSI

 

No but my muffler guy put the O2 bungs fairly far from the f body exhaust manifolds (about 1 ft.) The O2 sensor wires are not extended.
And I only get the code on cold startup. My understanding is that resistance is measured initially on cold starts and that's what's out of range and sets the code.

 

ttt,
any other suggestions?

 

Any correlation to cold soak ambient temp at startup?

 

All three occasions were cold start after sitting at least 24hr. Car ran fine, cleared codes, CEL didn't come back on for over a week.
I got under the car today, checked for voltage at the connector, replugged everything in. We'll see, maybe just corrosion or loose plug.

 

Wishful thinking. 4th time on cold start this morning.
Clear codes, they dont return. O2 sensor voltage looks fine so I'm assuming it's going into closed loop.
Anything else to check?

 

Hi Gary, did you ever figure this out? My 68 C10 with LS2 and Speartech harness and E67 computer is doing the same thing! Only on cold starts, clear the codes and they don't come back until the next cold start, but not always.

I have emailed John at Speartech, just waiting for him to reply.

Greg

 

I was trying a couple different tunes (not related to the O2 sensors). When I swapped to a new ecu, it went away and never returned.

 

Thanks for the update, maybe something that can be tuned out? Will see what John thinks.

 

Received an email from John over at Speartech, this is what he has to say.


Those are fairly minor codes that may be due to aftermarket O2 sensor variations or something similar.

They could probably be taken care of thru reprogramming.

 

Hi Gary, I have the exact same issue with a swapped LS in my land cruiser, did the new ECU end up being the long term fix? I'm looking at grounding, even questioning the starter motor etc, but if it's an ECU that's required, happy days.
Thanks.

 

Different ecu, not because of the O2 issue, fixed the issue. I swapped between auto and manual ecus, both reprogrammed for my install. Maybe imits of O2 cel are different between the 2 and not changed?