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Code P0300 P0301 P0302

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by andyg, Jan 1, 2020.

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  1. andyg

    andyg Junior Member

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    I left my 2008 Prius (215K miles) unused for a week before the Christmas holidays. When I started the car upon my return, there was an audible misfire for about 10 seconds and then the engine seemed to fire properly. I have a ScanGuage II attached and it showed me the codes P0300 P0301 P0302. I cleared the codes to see if the problem would occur again but everything seems ok thus far (I may have driven the car for 30 miles during the holidays since I first observed the codes). I drive 80 miles a day commuting to work and would like some advice from this forum on any preventive care I can do to prevent code p0300 again. I have changed sparks (oem NGK), both water pumps, coolant, Trans fluid and serpentine belt around 180K miles. I get over 50 MPG in summer and about 46 MPG in winter, in central Jersey. I am still running on the original hybrid and 12V batteries. I monitor both batteries when I drive and they seem to be holding up well. The hybrid battery maintains a charge around 60% while driving and the 12V hovers between 13 and 14 volts when driving. If changing the 12 volt is recommended, should I go for the Optima? My local dealer recommends another brand which seems a bit cheaper than the Optima. I forget the brand but the dealer says it is not OEM.
     
    #1 andyg, Jan 1, 2020
  2. RobertK

    RobertK Member

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    The fact that your 12V battery is holding between 13-14 volts indicates that the charging circuit is working. It does not give you any indication of the viability of the battery. My 2007 never shows less than 13.8V when in Ready mode, and goes over 14 when the battery is low.

    You are probably due for a 12V battery due to its age alone, but I don't think is is the cause of your misfire problem. I've had an Optima for 8 years and it is still holding 12.6 volts after sitting overnight and checking it with a multimeter before touching the car. Others on this forum have good luck with OEM, but I had to replace mine after 4 years. When I replace mine again I'll pick an AGM battery based on price, warranty, OEM fitment, and local availability.

    Since you recently replaced the spark plugs you should check the wiring connections to the coils on each plug. I would clear the codes and see if the condition occurs again. I would also check for water in the plug holes that might have gotten in there while the car was parked.
     
    #2 RobertK, Jan 1, 2020
  3. andyg

    andyg Junior Member

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    Thanks, I will check the wires. I normally park the car outside but had it parked inside my garage when I went out of town. I have cleared the codes and they have not appeared again, as yet.
     
    #3 andyg, Jan 1, 2020
  4. andyg

    andyg Junior Member

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    It's been a month since I cleared the codes P0300 P0301 P0302, and I haven't seen any error codes in my scanguage2 so far. I am averaging 47mpg which is my typical average every winter. Hopefully it means my wires are OK. I would still like to change my 12V battery given its age. Any recommendations please? My original still shows a steady 13.7V when running. I have not measured the voltage before turning the car on.
     
    #4 andyg, Feb 2, 2020
  5. eternalphoenix64

    eternalphoenix64 Junior Member

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    Five
    I would go with the Toyota battery, personally. But when I was looking for one, my local dealer was the cheapest of all the options. It was something around $250 after tax and all my other options were $300+ BEFORE tax.

    Fun things happen when a car has been sitting for a while. You may have a slight leak in a couple of the valve cover gasket grommets, or the coil heads. If water and/or oil get in the spark plug wells, they can interfere with the electrical signal for the spark plug causing a misfire. It's also possible for some leaking into the cylinder if the spark plugs aren't properly tightened.

    All that means is that when the car sits a long time or gets a heavy water dump from weather, it could cause misfires, and is generally not something to be concerned with if it doesn't come back in a short period of time.
     
    #5 eternalphoenix64, Feb 2, 2020
  6. andyg

    andyg Junior Member

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    #6 andyg, Feb 2, 2020
  7. andyg

    andyg Junior Member

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    Thanks ! Ironically, I park my car in the driveway rain or snow. This one time when I parked the car inside the garage and went out of town for a week, it acted up on my return. My local Pep Boys in NJ has "Optima Yellowtop Prius Deep Cycle Car Battery, Group Size DS46B24R" for $238. Has anyone had issues with this Optima on a Gen II? I have yet to check with my local dealer. If I can give my friendly local auto store my business, I'd like to try the Optima.
     
    #7 andyg, Feb 2, 2020
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