Hi all, First post. I have a 2001 Prius with about 175K miles on it. I was headed to the beach this past Tuesday and had an oil change done right before I left. The trip here from NC to Myrtle Beach was about 200 miles. On the way back today, after I stopped to fill up on gas the 'check engine' light came on for the rest of the trip back home. I went tonight to Autozone and got back all the codes that are in the subject line above. My question is...Is it possible that all of those codes are somehow the result of my recent oil change? (Oil overflow?, etc.) I've been doing some searching in the archives for those codes and oil/fluid changes appear to be a possibility with all of them. Just a little background, I've already had the hybrid battery replaced in this car a little more than a year ago. I've had no more warning lights come on since that time until today. Thanks to anyone who can offer some insights! Jeremy
1. I doubt that an oil change would cause a misfire (the P030x DTC) problem but it is easy enough for you to check the engine oil level. 2. When was the last time you had the iridium spark plugs changed? The service interval is 60K miles for Classic. 3. DTC P0420 means a failed catalytic converter which at your odometer reading is certainly plausible.
Hi folks, I would like to resurrect an old thread if I may. My car is past due inspection and I can't get the CEL to cooperate with me this time around. My main code is p0420 (it always pops up first) followed by p0440, 0441, 0446. Couple of questions... I am aware that a p0420 points to the catalytic converter - my Prius is an '01 that has more than 200K miles and the CC has never been replaced. I've read different things online about trying other things before a last resort of replacing the CC. Does anyone concur with this and have any suggestions? My nightmare scenario is replacing the CC and not having it do a thing for the CEL. Also, what is the thought on aftermarket CCs for the Prius? My main concern is being able to pass inspections. I've had the p0420 code for a couple of years now and have noticed a 4-5 mpg drop in gas mileage (from ~ 52 mpg in summer to ~ 47-48 mpg) so nothing really significant performance wise. Finally, is there any chance that the evap codes (0400s) are related to the 0420 code? Again, going back to trying to pass inspection, if I could get my evap monitor to show ready I wouldn't have to worry about my catalyst monitor. Any help would be appreciated! Jeremy
As stated in the previous post, it could be O2 sensors telling your car the cat is bad. I faced the same dilemma recently with my old car. My research showed quite a few aftermarket cats are only good for a couple years of inspection before they don't perform well enough. Magnaflow was rated pretty well out of the bunch from what I could gather. OEM is obviously best, but big $$.
Bob, I have a scanner but am having difficulty using it anywhere other than plugged into the car. Can you tell me what I'm looking for when it comes to the O2 sensors? I will try to monitor it while driving...
I'm in the same predicament with my 01 classic needing to pass emissions test. Local tech showed me on the scanner how the downstream O2 sensor is indicating weak CC. I've already replaced both O2 sensors (and cleaned the throttle body, replaced 12v battery, air filter, iridium spark plugs, MAF sensor (for other recent DTCs)) As for the CC, have you found a reasonable resolution? I mean who wants to spend a grand on exhaust for a 13 y/o car that is now prone to mechanical issues? ... other than the fact that it sips gas. Anyway, I'm trying to decide to go with OEM or aftermarket CC. Any info would be appreciated.
I think you should have an exhaust system shop install an aftermarket catalytic converter but that will require some welding. The original cc will have to be cut off and the replacement welded in, so that the HCAC valve which is upstream from the cc can be retained. The HCAC valve is one reason why the correct Toyota catalytic converter is so expensive, since both are included in the one assembly. Don't expect the aftermarket cc to last very long, but what do you expect for ~$300.
Roy from canada -- here is info from my service manual: P0420 Catalyst System Efficiency Below Threshold (Bank 1) _ Gas leakage on exhaust system _ Open or short in heated oxygen sensor circuit _ Heated oxygen sensor _ Three–way catalytic converter _ _ P0440 Evaporative Emission Control System Malfunction _ Hose or tube cracked, hole, damaged or loose seal _ Fuel tank cap incorrectly installed _ Fuel tank cap cracked or damaged _Vacuum hose cracked, hole, blocked,damaged or disconnected _ Fuel tank cracked, hole or damaged _ Charcoal canister cracked, hole or damaged _ Open or short in vapor pressure sensor circuit _Vapor pressure sensor _ Fuel tank over fill check valve cracked or damaged _ECM _ _ P0441 Evaporative Emission Control System Incorrect Purge Flow _Vacuum hose cracked, hole, blocked damaged or disconnected _ Open or short in vapor pressure sensor circuit _Vapor pressure sensor _ Open or short in VSV circuit for EVAP VSV for EVAP
Roy from canada - More info on po 420 DTC P0420 Catalyst System Efficiency Below Threshold CIRCUIT DESCRIPTION The ECM compares the waveform of the oxygen sensor located before the catalyst with the waveform of the oxygen sensor located behind the catalyst to determine whether or not catalyst performance has deteriorated. Air–fuel ratio feedback compensation keeps the waveform of the oxygen sensor before the catalyst repeatedly changing back and forth from rich to lean. If the catalyst is functioning normally, the waveform of the oxygen sensor behind the catalyst switches back and forth between rich and lean much more slowly than the waveform of the oxygen sensor before the catalyst. But when both waveforms change at a similar rate, it indicates that catalyst performance has deteriorated
Thanks Patrick and Roy for your replies and info. It's unfortunate that I had installed a inexpensive salvage exhaust (from a guy I know, rust free, 03, low miles) to resolve the P1436 issue, but I'm still getting P0420 for the cat. 2 bad cats? Hmmm. It's possible. This may be beating a dead horse (or dead cat), but my understanding so far is that there're many variables concerning these emissions DTCs. Considering that I've already replaced the O2 sensors with OEMs, should I assume that a waveform comparison of the O2 sensors and a heat test of the cat are sufficient to conclude that the cause of P0420 is indeed a bad cat? Can a Toyota shop conduct any other diagnostics other than those above? Just checking before I go into installing a new aftermarket cat, which from what I understand may not keep the CEL away for long. I'm also considering selling this classic b/c my Gen II is so much more reliable and that is where I need to head from here. BTW, I'm posting my 01 repair record on your Classic Prius Repairs survey thread. Tom
Yes, if you have newly installed oxygen sensors the only other check I can think of is to hook up an oscilloscope to see that the upstream O2 sensor shows a rapid voltage fluctuation (which corresponds to the engine ECU operating in a feedback mode, continually varying the air/fuel ratio a bit rich then a bit lean.) The downstream O2 sensor should show relatively constant voltage which indicates the cc is doing its job. If you also see rapid voltage fluctuations from the downstream sensor then that is evidence the cc has failed. The above assumes that you've driven at freeway speeds 20 miles or so to make sure the engine and the cc are fully warmed up.
If you buy the mini vic techstream $30 from the internet and a old computer with 32 bit xt installed you can view the oxygen sensor readings as you drive as well as the mass air function readings. If you do that I can give you readings from one of my 2001 prius cars to compare. This may be of some help. Roy from canada
I replaced both o2 sensors and the MAF (mass air flow sensor) on one of my cars and the 420 code did not come back. You can but the MAF on the internet for under $30 (chinese made). I bought 3 and replaced the MAF sensors on all 3 cars (2 were working OK) and they perform as good as the originals.
Will any tech actually take the time to drive 20 mins on the freeway? The local tech did this while idling after I drove only 10 mins to the shop and it sat cooling for a while. He said he saw enough fluctuation in the d/s O2 sensor to indicate the cc is not working properly. Then checked the heat coming from the cc with a... lazor(?) That is it, for $74.
[QUOTE="royfrontenac, post: 2013441, member: 120862 I replaced both o2 sensors and the MAF (mass air flow sensor) on one of my cars and the 420 code did not come back.[/QUOTE] Thanks. I did replace the MAF sensor recently for the P0171 and it didn't come back, but 0420 did.
I am not a mechanic, just a handyman with a garage so my help is limited to my repairs on my cars. I purchased the techstream software and cable off the internet and it allows me to see o2 readings as well as many other functions on the car. It sounds like you have replaced both o2 sensors and the MAF sensor the same as I did and still have the problem. Cannot be of much more help at this time. Roy
Update: With both O2 sensors already installed, and cat. converter (CC) proving inefficient, I purchased an Eastern Echo II 40544 direct fit CC and had it mounted and welded on the output pipe. After clearing the code, completing the "drive cycle", ensuring the "ready state", with no further CEL, I passed the emissions test 23 Jun 14. Praise the Lord! Thanks to all who helped me out here too - I'm grateful for all of you. BTW, I learned in the process that the sooner one resolves emissions problems (DTC's) upstream (air/fuel/electrical issues), the better chance of preventing damage downstream (O2 sensor and CC).
