Take a look at the picture I have attached; it will tell the entire story. That'* the HO2S.

Replaced with a 'used' but good, and the P0171 code went away, and SES light went out almost immediately.

I did take the step of replacing the plugs and the positive battery cables to starter (crank test showed 0.7 volt drop on original cable) and firewall. The firewall cable I did a 'special' mod, re-routing it over the engine between the alternator and LIM, and splicing the alternator lead into the center of the cable. I kind of wish the voltage regulators were 'adjustable', but I did buy the pigtail so I could eventually mod the regulator to take the input voltage from the firewall. With my new cable installation, I'm not sure that will help much, because there should be zero voltage difference between the Alt and the Batt and the firewall now.

It is worth noting that I replaced three of the plugs, and both battery cables (including Alternator Cable Mod) and it did not affect the Lean condition the HO2S was giving due to the broken welds on the sensor. But, it is all good, and I'm glad I did it.

Ya, that would do it. Good to hear you found it and fixed it.

Was this the upstream or the downstream O2 sensor?

Hi dwitos1,

This thread died over seven years ago so it'* likely not being monitored. I looked the OP'* car up and it looks like it only has one oxygen sensor. It'* pre-OBD2 so that makes sense.

If you have further questions etc., please start a new thread in the appropriate forum.

Thanks, and welcome aboard!