Service engine light
Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
Service engine light 
Just got my car running and put about 100 miles on the new build and my service engine light came on . I took it to a local autoparts to pull the codes and these came up.
I put new 02 sensors ac delco brand on this new build.
This is what i got on my 97ss
355 stock crank forged rods and pistons compression around 11.4
LE2 heads and cam, ported intake, new ngk plugs and msd wires., the good ones 😁.
Crs water pump
OBX long tubes and 3" ory into stock slp muffler
Deleted second set of o2 sensors
Yank 3600 on stock a4
Pcm for less tune
Listed mods just in case someone asked
Cars running a little rich even after its reached 160°
Appreciate any advice on how to resolve my engine light issue
Thanks in advance
TECH Resident
Joined: Jul 2007
Posts: 967
Likes: 53
From: Winter Haven FL
AC pressure is just telling you that you have a freon leak.
The O2 sensors not reading make me think that you plugged the new front sensors into the rear connectors. Either that or someone swapped the front and rear wiring to reach on long tube headers and you're going to have to swap the wires back at the pcm
The O2 sensors not reading make me think that you plugged the new front sensors into the rear connectors. Either that or someone swapped the front and rear wiring to reach on long tube headers and you're going to have to swap the wires back at the pcm
Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
AC pressure is just telling you that you have a freon leak.
The O2 sensors not reading make me think that you plugged the new front sensors into the rear connectors. Either that or someone swapped the front and rear wiring to reach on long tube headers and you're going to have to swap the wires back at the pcm
The O2 sensors not reading make me think that you plugged the new front sensors into the rear connectors. Either that or someone swapped the front and rear wiring to reach on long tube headers and you're going to have to swap the wires back at the pcm
And i believe there is no way to plug the front sensors into rear connections because the connection is different .
Ones kind of square and the other is like an oval connection
Well i have the oval connections hooked up.
Did i connect the wrong ones?
I was told the other ones with small square connectors would be deleted with the tune.
Thanks
Last edited by 97sswcubes; Mar 17, 2019 at 07:55 AM.
TECH Apprentice
Joined: Mar 2011
Posts: 324
Likes: 25
From: Waterford, MI
Both codes are for the upstream O2 sensors, Bank 1 and 2. Since both sensors are new and both sides are throwing a code for what seem to be a sensor related fault, not necessarily something air/fuel related, I'd almost wonder if it has something to do with the tune you got?? Is it possible the sensors got banged around at all at any point to where they may have been damaged? Do you have other known good sensors you can swap out to try?
Could it be the parameters in the tune are backwards, meaning front is rear, rear is front? Not sure how that works since I've never tuned a PCM myself, so I'm spitballing here.
Try resetting the PCM (battery disconnect) and see if they come back.
Edit: I don't think any of them have a 4 pin straight connector, all I'm seeing online is the 4 pin square connector for both upstream and downstream. They're all showing the same part number as well.
Could it be the parameters in the tune are backwards, meaning front is rear, rear is front? Not sure how that works since I've never tuned a PCM myself, so I'm spitballing here.
Try resetting the PCM (battery disconnect) and see if they come back.
Edit: I don't think any of them have a 4 pin straight connector, all I'm seeing online is the 4 pin square connector for both upstream and downstream. They're all showing the same part number as well.
Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
Both codes are for the upstream O2 sensors, Bank 1 and 2. Since both sensors are new and both sides are throwing a code for what seem to be a sensor related fault, not necessarily something air/fuel related, I'd almost wonder if it has something to do with the tune you got?? Is it possible the sensors got banged around at all at any point to where they may have been damaged? Do you have other known good sensors you can swap out to try?
Could it be the parameters in the tune are backwards, meaning front is rear, rear is front? Not sure how that works since I've never tuned a PCM myself, so I'm spitballing here.
Try resetting the PCM (battery disconnect) and see if they come back.
Edit: I don't think any of them have a 4 pin straight connector, all I'm seeing online is the 4 pin square connector for both upstream and downstream. They're all showing the same part number as well.
Could it be the parameters in the tune are backwards, meaning front is rear, rear is front? Not sure how that works since I've never tuned a PCM myself, so I'm spitballing here.
Try resetting the PCM (battery disconnect) and see if they come back.
Edit: I don't think any of them have a 4 pin straight connector, all I'm seeing online is the 4 pin square connector for both upstream and downstream. They're all showing the same part number as well.
The square connector 02 sensor is the one that i should have instead of the ones i have on there now? (straight 4 pin like in the picture above)
As some backup info
I had a header flange exhaust leak and was causing a bad misfire , car was running like crap.
Running really rich. Finally changed the header gasket and mis went away and was burning the gas clean.
But a few days ago it started running rich again but no misfire then check engine light came on.
Im thinking that exhaust leak might have come back even though i cant even pick it up by ear. Aslo gettin pretty bad fuel mileage.
So to clear things up when you mod an lt1 and strip off all emission components install long tubes no cats and get a mail order ecm tune
What 02 sensors are deleted? The square port connector or the straight 4 pin connector?
Thanks for the info as i work on my car and dont take my car to no shop.
Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
Hm, im confused. So what you are saying is i have hooked up the wrong o2 sensors?
The square connector 02 sensor is the one that i should have instead of the ones i have on there now? (straight 4 pin like in the picture above)
As some backup info
I had a header flange exhaust leak and was causing a bad misfire , car was running like crap.
Running really rich. Finally changed the header gasket and mis went away and was burning the gas clean.
But a few days ago it started running rich again but no misfire then check engine light came on.
Im thinking that exhaust leak might have come back even though i cant even pick it up by ear. Aslo gettin pretty bad fuel mileage.
So to clear things up when you mod an lt1 and strip off all emission components install long tubes no cats and get a mail order ecm tune
What 02 sensors are deleted? The square port connector or the straight 4 pin connector?
Thanks for the info as i work on my car and dont take my car to no shop.
The square connector 02 sensor is the one that i should have instead of the ones i have on there now? (straight 4 pin like in the picture above)
As some backup info
I had a header flange exhaust leak and was causing a bad misfire , car was running like crap.
Running really rich. Finally changed the header gasket and mis went away and was burning the gas clean.
But a few days ago it started running rich again but no misfire then check engine light came on.
Im thinking that exhaust leak might have come back even though i cant even pick it up by ear. Aslo gettin pretty bad fuel mileage.
So to clear things up when you mod an lt1 and strip off all emission components install long tubes no cats and get a mail order ecm tune
What 02 sensors are deleted? The square port connector or the straight 4 pin connector?
Thanks for the info as i work on my car and dont take my car to no shop.
I do have the correct 02 sensors on there.
Now to find out why im getting the codes and running rich.
LT1's had flat connectors for the front O2's, they changed it in 98. OBD2 LT1's had square connectors on the rear O2's.
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Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
Well, just like to post an update.
Today i took off the driver side header off again and checked the gasket..
Looks like it was leaking again. Im using fel-pro 1406
That last time i replaced the header gasket i used some copper rtv hoping it would help sealing between the flange and head. Well it didn't work.
So today after washing my truck, mowing the lawn i made some time to change out the gasket again.
This time i doubled the gasket.
Dont know if it's gona work im hoping it will
If someone's done this before and had positive results please chime in and let me know.
I took out the ecm fuse to reset it and driving the SS to work tomorrow see how it runs.
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Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
It might be. I actually bent that header a little when i was installing the engine. I accidentally lowered the engine too much at some point and the header leaned against the car and the tubes of the header bent towards the engine.
Weird part is it seems it only leaks from that one exhaust port as you can see in the pictures.
Weird part is it seems it only leaks from that one exhaust port as you can see in the pictures.
Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
Gona give it a few heat cycles and retightened it.
Is there such thing as too tight?
Stainless steel obx.
Thread Starter
Teching In
Joined: May 2018
Posts: 46
Likes: 1
Well i got an update.
I swapped out the noisy alternator for a new ac delco and i have to say it made a difference.
Cars exhaust sounds fuller and it reves very smooth without hesitation.
I guess the knock sensor was picking up noise from the old alternator.
How noisy? Guys at work would ask me if i had a supercharger....
I'll take it out for a drive this afternoon see how it handles.