72chevelle6.0

iTrader: (22)

ok here is the deal.

We installed a 2002 5.7 ls1 in a 1983 jeep using an 02 5.3 harrness and a 02 5.3 ECM with a 5.7 tune flashed on it. well the motor starts fine and idles fine but when we scan it the 02 sensors do not move up and down like the other logs I have seen or I have logged they just sit at 445 maybe changing +/- 4.

We have check and rechecked the wiring harness and the ECM Plug and that is all correct.. also for giggles we unplugged the 02 Sensors and the reading is still the same. this makes me think that we have a short some where..

What do you guys think?

Redbull87

iTrader: (3)

Id check your grounds at the back of the heads for starters.Since unplugging both o2 sensors and no mil light came on..your issue is elsewhere.If the grounds check out ok then id worry about the ecm itself if its in good shape or the tune could have simulated reading set in it.Who flashed it? being flashed for 5.7 isnt enough detail on how it was setup :S Were the o2 sensors tuned out?

72chevelle6.0

iTrader: (22)

I will recheck the grounds. we did do a beep test between the connectors and ground which was good.. I flashed the 5.7 tune on it which came from my bothers 2002 TA. it was his stock tune.. but yes when we unplugged the 02 it stayed the same reading with no DTC..

Redbull87

iTrader: (3)

Are you using 2 pre and 2 after cat o2 sensors..it may be looking for all 4 and your probably using just the fronts correct? Big thing is its not setting a dtc..which it should!

Thought I will say checking grounds with just the "beep" on a multimeter does not mean its a sufficient ground..it can still have high resistance and make continuity from one end to the other.Im still leaning towards having that ecu/tune checked though.Hope you find the issue.

72chevelle6.0

iTrader: (22)

we are using the 2 per cat sensors.. I turned off the two rear ones.. I have also checked to see if the fronts are set to turn on the MIL Light and they are.. I will check the grounds again and update the post.