2010 Prius with possible clogged EGR

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Newpriusowner91, Jun 26, 2026.

  1. Newpriusowner91

    Newpriusowner91 New Member

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    Vehicle:
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    II
    Hi all, I’m a new Prius owner as of last week. I bought it used from a small independent owned dealership. 2010 Prius with 186k miles on it. Second day of owning it the check engine light popped on. Went to auto zone and the code P0401 popped up. I contacted a few mechanics near me and both had no desire to clean the EGR or even look at it! I found a mechanic literally 2 minutes from my house who said he does do EGR cleanings and repairs and to drop the car off on Monday.

    I’m obviously worried what this will cost me. Google and a few Reddit peeps told me to clean it the range is $600-900 and a full repair is $1500 average. I’m not too happy but I love this car! I’ve only had it a week and I love it, I’m getting 44 miles to the gallon ( I drive around town that’s about it) I haven’t taken it in the highway yet because I’m worried about this EGR or whatever it could be causing the engine light to pop on.

    If the EGR is the reason for the light should I get it cleaned every 50k miles? I hope to keep this car for years. I have it paid off so at least whatever goes wrong I can fix and not worry about making monthly payments for a car that is old with a lot of miles on it.
     
    #1 Newpriusowner91, Jun 26, 2026
    bisco likes this.
  2. bisco

    bisco cookie crumbler

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    congrats and welcome! no warranty from the seller? you'll need a code reader for the engine light, could be as simple as a loose gas cap
     
    #2 bisco, Jun 26, 2026
  3. ChapmanF

    ChapmanF Senior Member

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    Two conditions can contribute to low EGR flow and a P0401 code: clogging, and a rutted ski jump in the valve actuator. You might have either one or both. Whoever looks should check for both.

    Of course, the extra-simple causes are also worth checking, like something just plain stuck, or an issue in the electrical circuit (which would give P0403 if obvious enough for the car to detect it).
     
    #3 ChapmanF, Jun 26, 2026
  4. 20113rdgen

    20113rdgen New Member

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    Second day? The guy trading it in likely scammed the dealer, who went on to scam you (deliberately or not)

    90% of the time you are better off cleaning it yourself to save the money. Only tricky(nightmare) part is the egr cooler bolts
     
    #4 20113rdgen, Jul 2, 2026 at 8:07 AM
    CR94 likes this.
  5. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Vehicle:
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    Model:
    Touring
    One bolt in particular. More accurately, one nut-on-stud, highlighted in yellow:

    upload_2026-7-3_8-52-56.png

    Make it easier on yourself, remove that nut, and the associated stud, in advance of the main job. It can be done without any other disassembly, and both the nut and stud can be left off permanently. This has the side benefit, of allowing the two studs at the rear of the cooler to remain installed, which in turn helps retain the rear gasket as you pull the cooler out, and retains/aligns the gasket during subsequent reinstall.

    At that same prelim nut/stud removal, it's good to "dress rehearsal" the similar nut/stud combo going through the EGR valve, and the bolt at the top EGR cooler bracket: remove them, add a thin/uniform skin of anti-seize (work into the threads with an old toothbrush or similar), and reinstall, slightly shy of torque value.

    Also, on the day of the main job, before doing anything else, drain two quarts (or litres) from the radiator bottom spigot, into a clean container (pour it back into reservoir when done). This'll drop the coolant level below the EGR components, avoid virtually all spill when cooler coolant lines are pulled off.

    Also, there's no need to disconnect throttle body coolant lines; the throttle body can be lifted off with them attached, tied to the inverter wiring harness.

    Then, no nightmares.
     
    #5 Mendel Leisk, Jul 3, 2026 at 12:03 PM
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