Downstream 02 issue
Thread Starter
5th Gear
Joined: Jun 2025
Posts: 5
Likes: 0
Downstream 02 issue
Hello all,
I have a 2015 Stingray that I am having some issues with. I had headers and exhaust installed and all, upstream and downstream, O2 sensors were supposed to be installed due to emissions testing where I live. To make a long drawn out ridiculous story short I got out of the car found my Downstream O2s were missing and still in the factory exhaust. I attempted to install them and the pigtails were too short due to the location of the bungs in the new exhaust. Because I just needed to pass emissions I attempted to lengthen by soldering and splicing without using the proper wire or hear insulation. It worked I passed emissions however 3 miles down the road my connections melted away leaving a bigger problem.
When the wires burned up it shorted everything out. I replaced the 02 sensors and did a proper extension however only one of the two downstream are reading. I have replaced one fuse associated with the 02 sensors I cannot find any others.
help pointing me in the right direction of a solution woukd be appreciated
I have a 2015 Stingray that I am having some issues with. I had headers and exhaust installed and all, upstream and downstream, O2 sensors were supposed to be installed due to emissions testing where I live. To make a long drawn out ridiculous story short I got out of the car found my Downstream O2s were missing and still in the factory exhaust. I attempted to install them and the pigtails were too short due to the location of the bungs in the new exhaust. Because I just needed to pass emissions I attempted to lengthen by soldering and splicing without using the proper wire or hear insulation. It worked I passed emissions however 3 miles down the road my connections melted away leaving a bigger problem.
When the wires burned up it shorted everything out. I replaced the 02 sensors and did a proper extension however only one of the two downstream are reading. I have replaced one fuse associated with the 02 sensors I cannot find any others.
help pointing me in the right direction of a solution woukd be appreciated
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,433
Likes: 3,981
From: Cape Coral, Florida
The O2 sensors have 4 wires...2 for the sensor that reads the oxygen and the other 2 are for the heater circuit...if you have a scan tool or even a code reader when the engine is cold and the ignition is on you should see 450Mv's which is their bias voltage...what are you reading ??...if you see 450 the wiring is fine...if it is not disconnect the O2 sensor and now read the bias voltage...is it 450 or something else ???
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,433
Likes: 3,981
From: Cape Coral, Florida
The sensor signal wire is most likely shorted to power which is the power feed for the heater circuit...as mentioned disconnect the sensor and still see if it still reads 1.275 volts...that voltage is the max that the ECM can read as it will not read 12 volts......the violet/blue heater power feed is shorted to the violet/blue or violet/green depending which bank it is.
Last edited by C5 Diag; Jun 30, 2025 at 02:53 PM.
Thread Starter
5th Gear
Joined: Jun 2025
Posts: 5
Likes: 0
The sensor signal wire is most likely shorted to power which is the power feed for the heater circuit...as mentioned disconnect the sensor and still see if it still reads 1.275 volts...that voltage is the max that the ECM can read as it will not read 12 volts......the violet/blue heater power feed is shorted to the violet/blue or violet/green depending which bank it is.
are you saying to check the voltage at the plug once O2 is disconnected or to disconnect O2 and view live data ?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,433
Likes: 3,981
From: Cape Coral, Florida
If the O2 sensor is unplugged and you are seeing 1.275 volts with your scan tool the problem is in the wiring…let’s say you are seeing 1.275 volts with it plugged in and now you disconnect the sensor and now you are seeing 450 mv’s the problem is with the sensor and not the wiring.
Last edited by C5 Diag; Jul 5, 2025 at 09:52 AM.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,433
Likes: 3,981
From: Cape Coral, Florida
In that case you have the signal wire shorted to the heater power wire on both…with no sensor installed seeing 450 mv’s tells me the wiring is good.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,433
Likes: 3,981
From: Cape Coral, Florida
No, it most likely is a short to power and not ground so you wouldn’t check continuity to ground…with your scan tool hooked up and reading 1.275 volts remove fuse 36 (Eng O/S Pos fuse 15A) and you should see that voltage disappear…that fuse powers both downstream O2 heater circuits.