Battery Replacement Caused a P0303 Code... Is This Possible?
Thread Starter
4th Gear
Joined: Dec 2009
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From: Sarasota, FL
Battery Replacement Caused a P0303 Code... Is This Possible?
Hi there... I'm at a loss here... I haven't driven my 2001 Corvette for over two years. It has 69K miles on it...I would warm it up every two weeks and it would run and idle perfect! A couple of weeks ago the battery went dead and I decided to replace the battery with an Optima Yellow Top Deep Cycle battery. Again, the 'Vette was running perfect before replacing the old battery. Once I installed the new Optima and started it, I immediately noticed that the idle was all out of whack! I hooked up an OBDII reader which indicated a P0303 Code was the reason for the misfire on cylinder 3. Has anyone heard of this happening before? Any input would be greatly appreciated! I was told to go ahead and completely drain all current from the vehicle which would cause all the electrical components to RESET themselves to factory settings and then go ahead and connect the new battery again. All electrical components should boot up perfectly! I am going to attempt this in a few days...I would really like to hear what anyone else thinks about this... Thanks in advance... Stay safe... Rico
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Changing the battery shouldn’t throw a misfire DTC...the crankshaft sensor monitors misfires so maybe just a hiccup there !!...has the same tank of gas been in the car for 2 years or longer ???...I’d get rid of all that fuel and put Techron or BG44K in the tank...maybe a clogged injector but I’m only guessing..also by disconnecting the battery the PCM will have to do it’s “idle relearn”
...it may run crappy for a bit !!...the PCM has no “factory settings” per se !!
...it may run crappy for a bit !!...the PCM has no “factory settings” per se !!
Last edited by C5 Diag; May 3, 2021 at 10:43 PM.
Thread Starter
4th Gear
Joined: Dec 2009
Posts: 4
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From: Sarasota, FL
Thank you so much for your input! The gas in the tank has been well maintained and is up to par... The 'Vette is showroom in every way... Maybe it's just one heck of a coincidence that this cylinder 3 misfire happens to occur when I replace the battery, but it was strange. I'll start with the obvious, spark plug, wire, coil pack, etc... and see where that leads me... I'll post back and let you know... Thanks again Brother... Stay safe... Rico (Sarasota, FL)
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,633
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From: Cape Coral, Florida
If you’d want to bring your car by I can take a look at it !!
ps- always a good idea to include your location in your profile !!
ps- always a good idea to include your location in your profile !!
Last edited by C5 Diag; May 3, 2021 at 11:57 PM.
Thread Starter
4th Gear
Joined: Dec 2009
Posts: 4
Likes: 0
From: Sarasota, FL
Hey Brother... Thank you so much for the offer! I really don't want to drive it missing like this... I have a friend from one of the Corvette shops in Sarasota coming over to help me find the issue... He's been working on 'Vettes for over 30 years and he knows my 'Vette inside out... Hopefully he'll have no problem with this... Again, thank you so much! Maybe one day I'll drive down, with my wife, to Pioneer Pizza in Punta Gorda and we can have a couple of slices...my treat! Again, thank you so much! Stay safe... Rico
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,633
Likes: 4,079
From: Cape Coral, Florida
Would that be C&S Corvettes ??...not a problem but if he gets stumped give me a shout and we can put our heads together !!...fuel or ignition issues are pretty easy to diagnose using a scope but anything mechanical takes a little bit more work diagnostically speaking. Let us know what you find !!
Last edited by C5 Diag; May 4, 2021 at 02:53 PM.
1st Gear
Joined: Dec 2003
Posts: 1
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From: Walled Lake MI
Old Thread - same issue
Would that be C&S Corvettes ??...not a problem but if he gets stumped give me a shout and we can put our heads together !!...fuel or ignition issues are pretty easy to diagnose using a scope but anything mechanical takes a little bit more work diagnostically speaking. Let us know what you find !!
I know this is an old thread but I just got my 1999 convertible out of storage & got the same results when installing a new battery (DTC P0303). What was the final resolution? I hope it was simple. Thanks!
