Aggravated and stressed
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1st Gear
Joined: Apr 2024
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Aggravated and stressed
Had a CEL pop up last weekend ran the code it was a bad O2 sensor. Took it to a shop and had it replaced. When I picked the car up on Friday and started it, it started misfiring and shaking and the CEL came back on service rear axle and stabilitrak. The code was a PO300. The shop owner said it’s nothing they did to it because they never raised the hood on the car. Any suggestions on what it could be? It’s a 2019 grand sport with 41,000 miles.
Pro
Joined: Oct 2008
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From: Central Va
Drifting
Joined: Mar 2022
Posts: 1,403
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From: Indiana
Just because you get a code for an O2 sensor does not mean the O2 sensor is bad. The code is telling you it is getting bad information from the O2 sensor. That could be faulty wiring, either on the sensor pigtail, the feed, or a number of other things. That isn't how OBD2 works.
Some years ago a good friend was flown to Colorado to diagnose a Lambo Hurrican the dealer could not fix. Kept throwing codes for throttle bodies. Dealer had hung two different sets of throttle body's hoping new parts would fix the issue. Numerous other parts totally several thousands of dollars. Within 45 minutes of hooking up diag equipment and doing a little old school poking around he found a short in the wiring harness under the engine cradle. That short was throwing codes for throttle bodies. Fixed a bare wire with a .25 cent connector and the problem was fixed.
The list goes on.
Some years ago a good friend was flown to Colorado to diagnose a Lambo Hurrican the dealer could not fix. Kept throwing codes for throttle bodies. Dealer had hung two different sets of throttle body's hoping new parts would fix the issue. Numerous other parts totally several thousands of dollars. Within 45 minutes of hooking up diag equipment and doing a little old school poking around he found a short in the wiring harness under the engine cradle. That short was throwing codes for throttle bodies. Fixed a bare wire with a .25 cent connector and the problem was fixed.
The list goes on.
Race Director
Joined: Apr 2000
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From: Texas
These cars seem to hate non-OEM sensors. Did they replace the sensor with AC Delco or another aftermarket brand? This board is littered with threads of people having this issue.
As for misfire codes, check to be sure all the plug wires are fully seated on the coils and on the plugs.
Another thing to check is that the wires for the new sensor were routed correctly. Unfortunately more than one "mechanic" has incorrectly wires and they get torched by the exhaust. Only takes a couple minutes for the exhaust to get hot enough to burn one or more of the wires.
As for misfire codes, check to be sure all the plug wires are fully seated on the coils and on the plugs.
Another thing to check is that the wires for the new sensor were routed correctly. Unfortunately more than one "mechanic" has incorrectly wires and they get torched by the exhaust. Only takes a couple minutes for the exhaust to get hot enough to burn one or more of the wires.
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How old is your battery? Most of those codes can be voltage related.
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First thing to check is the health of your car’s battery.
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