04 TB LT all options

04 TB LT all option packages, Running boards removed (it was that or buy a suit and i "aint" buyin' no suit) has 53K miles and i use 89 octane 10% Ethanol fuel in Iowa.
I have changed the 02 sensor on the E/manifold due to a code and was wondering about changing the other if i have noticed a fuel economy change ,, i get 13.8 in town stop and go driving no more than 50 MPH for any length of time. and i get 17 - 18 Avg. MPG on the interstate ( semi-hilly 75-80 MPH). Last note for anyone who may wonder, the S.E.S. light flickers for an instant about 5 -7 miles after i start the truck for the first time during the day,no hard codes (im thinking it's at that point it switches from closed to open loop)..
should i replace the downstream one ?
TIA
Joz

04 TB LT all option packages, Running boards removed (it was that or buy a suit and i "aint" buyin' no suit) has 53K miles and i use 89 octane 10% Ethanol fuel in Iowa.
I have changed the 02 sensor on the E/manifold due to a code and was wondering about changing the other if i have noticed a fuel economy change ,, i get 13.8 in town stop and go driving no more than 50 MPH for any length of time. and i get 17 - 18 Avg. MPG on the interstate ( semi-hilly 75-80 MPH). Last note for anyone who may wonder, the S.E.S. light flickers for an instant about 5 -7 miles after i start the truck for the first time during the day,no hard codes (im thinking it's at that point it switches from closed to open loop)..
should i replace the downstream one ?
TIA
Joz



When was the last time you checked your plugs and wires? SES light flickering could be misfires. A plug could be going or wire has a crack.

When was the last time you checked your plugs and wires? SES light flickering could be misfires. A plug could be going or wire has a crack.
Thats a great suggestion, ill look into that asap. i figured that a misfire with OBDII would store a hard code but after reading this post i remembered that its not right, ill scan it and see if i have a misfore detection and go from there.

thanks again

joz

There are no plug wires on the I6 or the V8s available in TBs. They use a coil-on-plug design, but check the connections to the coil packs too. You have to remove the pack to get to the plug.

There are no plug wires on the I6 or the V8s available in TBs. They use a coil-on-plug design, but check the connections to the coil packs too. You have to remove the pack to get to the plug.

i noticed that today, plugs are greyish and the gap is still correct.

there are no codes stored in the ECM and my monthly onstar report had nothing also

*stumped*
joz