Check Engine + VSC = Code P0420

Asked by Feb 16, 2016 at 07:20 AM about the 2004 Toyota Highlander Base V6 AWD

Question type: Maintenance & Repair

I recently purchased this car, and today the check
engine light and VSC came on. I had Advance Auto
scan it and it came up with P0420. What are some
troubleshooting steps I can do before taking it in to
possibly replace the exhaust or cat? Other possible
reasons for this?

2 Answers

10,960

It wouldn't hurt to test fuel pressure to make sure you don't have leaky fuel injectors. unburned fuel can cause this problem too. also, the o2 sensors can be tested. It might not hurt to have the exhaust inspected and "sniffed " by a good muffler shop. this could give you a better picture of what is going on.

10,960

as far as the vsc code, you are going to need a more extensive scan than the little code reader that the auto parts stores use. It wouldn't hurt to have a quality shop scan it with their professional equipment. they can read "live data". this means that they can assess while the engine is running and give a good pic of all systems while they are operating.

Your Answer

Add photo

Related Questions

  • What causes check engine and VSC lights to come on? 106 answers

    what causes vsc+check engine light to come on together

    2005 Toyota Highlander

    -

    Maintenance & Repair

  • check engine VSC code for 2005 Highland 2 answers

    codes P0420 and P0430 indicated. I was told to add Sea Foam when I filled up with gas. will this help or what should be done.

    2005 Toyota Highlander Limited V6 AWD

    -

    Maintenance & Repair

  • p0420 code and stalling 5 answers

    When I first bought this car a year ago I had a light come on for p0171 for lean condition, so this is what I have done. I changed the o2 sensor before the catalytic because this is what I was told...

    2004 Toyota Celica GTS

    -

    Maintenance & Repair

  • p0420 Code is back after replacing CAT 4 answers

    About 5 months ago at 140K miles I had the downstream CAT replaced with an aftermarket one because of the P420 Code. The check engine light went away. 3 Months ago at 143,700 miles I had the flex ...

    2001 Toyota Camry LE

    -

    Maintenance & Repair

  • Camry 2001 P0420 check engine light issues 2 answers

    Does anyone has a fix for Camry 2001 P0420 check engine light issues? I did replace Front sensors ie: A/F ratio O2 sensors Toyota Brand, did replave Front CAT, and still has CEL on??? Thank you,

    2001 Toyota Camry LE

    -

    General

Search Toyota Highlander Questions

Toyota Highlander Experts

#1 Wendy Tucker
Wendy Tucker
Reputation 4,010
#2 Tom Demyan
Tom Demyan
Reputation 3,780
#3 Shawntele Lewis
Shawntele Lewis
Reputation 2,400
View All

Related Models For Sale

Used Honda Pilot
341 Great Deals out of 20,719 listings starting at $2,199
Used Toyota 4Runner
253 Great Deals out of 20,378 listings starting at $1,995
Used Toyota RAV4
591 Great Deals out of 69,049 listings starting at $2,350
Used Acura MDX
227 Great Deals out of 18,359 listings starting at $1,500
Used Nissan Pathfinder
266 Great Deals out of 21,931 listings starting at $2,250
Used Toyota Sienna
224 Great Deals out of 29,771 listings starting at $1,331
Used Toyota Camry
834 Great Deals out of 89,150 listings starting at $950
Used Honda CR-V
768 Great Deals out of 58,582 listings starting at $900
Used Ford Explorer
800 Great Deals out of 74,739 listings starting at $750
Used Toyota Sequoia
158 Great Deals out of 5,638 listings starting at $1,995
Used Jeep Grand Cherokee
1,005 Great Deals out of 73,106 listings starting at $950
Used Toyota Tacoma
500 Great Deals out of 38,896 listings starting at $2,900

Used Cars For Sale

2017 Toyota Highlander For Sale
14,300 listings starting at $27,488
2016 Toyota Highlander For Sale
26 Great Deals out of 1,241 listings starting at $23,985
2015 Toyota Highlander For Sale
42 Great Deals out of 1,746 listings starting at $20,435
2014 Toyota Highlander For Sale
32 Great Deals out of 1,294 listings starting at $18,000
2013 Toyota Highlander For Sale
70 Great Deals out of 1,538 listings starting at $12,995