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2010 Focus - random engine downshifting issue

123 Views 2 Replies 3 Participants Last post by  R.S.LOGAN
So ive been dealing with a really weird issue lately. At random points either while im driving or sometimes from the start of turning the ignition, my speedometer drops to 0mph and my RPM's shoot up. The car continues to drive it just pushes 5000 RPMs when I step on the gas going above 10 -20mph (granted the speed stays at 0 im just going off of feel). Today I changed the spark plugs and valve cover gaskets thinking its a misfire or leak issue but that didnt solve this problem. Something really weird happens alongside this phenomenon which is sometimes after its been in this weird downshifted mode for a bit, the wrench icon comes on and the car says im low on gas even though im not. And for a while to fix this weird problem I just had to turn the car off and on again but now its gotten to the point that that doesnt fix it half the time, I just have to wait for it to correct itself back to normal while im driving which usually always happens at some point. Something ive noticed when it punches back to normal is the doors all relock and then the speedometer shoots back up, so this is starting to feel like either a weird electrical issue or an issue with how the car is registering what gear its supposed to be in possibly? Also sometimes the check engine light comes on temporarily when this starts happening a bunch (this problem isnt consistent, sometimes it wont happen for a few days and other times it will happen everytime i turn the car on), today I did a check on the code for the check engine and it spit out the code "P0720 - OSS Sensor Circuit Malfunction" until we cleared the code, which now the check engine hasnt turned back on since. Also one last detail that may or may not be related to this is that I keep getting a message saying "Tire Pressure Sensor Fault" but this issue was happening a few days before that popped up. Im pretty broke at the moment and spent my last bit of money trying to replace the valve cover gaskets and spark plugs so im pretty desperate at this point to figure this out without needing to go to a shop possibly. So any insight into what might be causing this would be very helpful, thank you!
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Check all ground connections, battery connections AND condition FIRST. Battery should be holding a full charge and the alternator should be charging properly.
Assuming all that passes, sounds like a possible speed sensor issue, which goes along with the code you pulled. Check the plug connector on that for corrosion and broken wires.
Sometimes unplugging and re-plugging the connector a few times will temporarily resolve the problem.
Really needs scanned with Forscan to cover all modules / systems to avoid fitting possibly unneeded parts and subsequent costs
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