No Fuel trims or O2 switching...am I missing something in the tune?

[Blue Bee]

Hey guys, just did a BTR cam, clutch, overhaul trans and other work in which we dropped the entire drive train out on a friends '03 Z06. Car has had LG pro long tubes on it for years, we replaced the O2's and I had pulled the LG tune a few months back to make sure I could tune on the car with no weird issue. Well I have an issue, O2's not switching and no fuel trims. I've looked the tune over and can't seem to find what could be causing it to stay in OL. I had never scanned car before so I don't know if LG has done this or the O2's that we put in from the parts store which are technically rears using LG's front adapters...

j_johnson_tune_1.hpt
no LTFT.hpl

Any thoughts? Thanks in advance.

[5FDP]

You have a wiring problem, 450mv is a dead give away that you have no power running to the sensors.

[Blue Bee]

You have a wiring problem, 450mv is a dead give away that you have no power running to the sensors.

That's what I came to find out this morning...it was a late night. I needed to get another car done on the dyno but I'm gonna mess with it later. Do you know having them switched side to side would do that? I didn't take the exhaust off but I was confused looking at it because with LG's adapters to use rear on the front wiring, technically they are switched by LG because the right side plugs into left front? Does that make sense?

[2xLS1]

Incorrect crossed O2s on a Vette will drive the trims on one bank + and the other bank -.

[Blue Bee]

Incorrect crossed O2s on a Vette will drive the trims on one bank + and the other bank -.

Right, but it won't cause the O2's to be dead, or stuck at 450mV or so? In the log I forced closed loop but they still didn't move voltage.

[Blue Bee]

Does anybody know what the high/low signals should have for voltage? My "C" and "D" power and ground are good, 0.0 ohms to ground and battery voltage on pin D. I have 5.V on A and 4.5V on B.

[Blue Bee]

I wanted to bump this and let everyone know that I found the fix for this, it had nothing to do with wiring and everything to do with LG as stated in first post they use the rear O2's with adapters. This does not work, rear O2's heat faster and switch faster which can not be accounted for in the tune. LG tried in the tune but failed, so for the last 12 years this car never had fuel trims. I simply got front O2's and extensions, put the O2 airflow mode and some other tables back to stock looking at other vette tunes I had, fired it up and O2's worked perfect, started switching and car went into CL. So just in case anyone else has this issue, or just bought LG longtubes, ditch their adapters and rear O2's, get front and extensions if you want CL and fuel trims.

[Russ K]

I have LG LT headers, and I used their adapters to use the rear O2's. No issues going into CL. You probably had a bad O2, and an O2 code will prevent CL.

The right side O2 goes to the right side vehicle harness.

Russ Kemp

[2xLS1]

I've seen plenty of C5 vettes use rear O2s for fronts. Like Russ said the L&R banks plug into the opposite side harness because of the angle they come out of the pipe at. If I had to guess there uas probably a wiring error in the adapters. Heck, f-bodies with long tube headers use Vette rear O2 sensors all the time for fronts because of the long wire lengths. The sensors them self are no different than front O2s just longer wires and on the Vettes the plugs are different. On f-bodies the plugs are even the same front and rear.

[Blue Bee]

I have LG LT headers, and I used their adapters to use the rear O2's. No issues going into CL. You probably had a bad O2, and an O2 code will prevent CL.

The right side O2 goes to the right side vehicle harness.

Russ Kemp

Right, Fronts are correct for the side of the car they are on as far as wiring, which is how I had them, no DTC's, no CL. This was using brand new sensors, install old originals, same, no CL. Installed another set of rears out of a Vette I just did a couple weeks ago, same, no CL.

I've seen plenty of C5 vettes use rear O2s for fronts. Like Russ said the L&R banks plug into the opposite side harness because of the angle they come out of the pipe at. If I had to guess there uas probably a wiring error in the adapters. Heck, f-bodies with long tube headers use Vette rear O2 sensors all the time for fronts because of the long wire lengths. The sensors them self are no different than front O2s just longer wires and on the Vettes the plugs are different. On f-bodies the plugs are even the same front and rear.

O2 design has changed over the years, I'm aware they used to be the same plugs but the research I came up with found that on this car the front and rears are actually designed different and operate different. I double checked the adapters to make sure they were wired correctly, they were based on front wiring diagrams and rear O2 diagram. If I'm wrong then how does it work by simply plugging in actual front O2's versus rear? It's water under the bridge now, it works, customer is happy, I'm happy...except for the fact that the stock injectors are not cutting it...need bigger. I didn't realize this car still had stock injectors...