Hi everyone, I just got off the phone with a muffler shop and need to get some "informed" opinions about what to do for my '01 Prius. My prius has been putting out codes of p0420, p0440, p0441, and p0446 for a while. I have a code reader and when I would reset the CEL, these codes would come back like clockwork. The last couple of weeks I had to do some driving in the mountains (in the cold) and noticed (what I believed) to be the catalytic converter getting worse -- getting louder going up hills, a new type of "whining" sound when I first started out at high speeds that would go away after a couple of minutes. Finally, over the weekend the car was driving fine for ~100 miles on the interstate. When I stopped to pick someone up (never turned off the engine), a couple of miles down the interstate after we left, the car started hesitating and not wanting to accelerate...also the CEL started flashing. I pulled off the next exit and got some gas since I was very low, but the symptoms stayed. I was able to get back to the car of the person I had met and left my car for a few hours. When I cranked it back up, it started shuttering and shaking and was not going to be driven anymore. My original thought was something with the 0440 EVAP codes, but my tow truck guy said that sounded like the catalytic converter and since I've had a 0420 code for the longest time, I had it towed to a local muffler shop. The CC has never been replaced and the car has more than 250K miles on it. So I know the CC is way past due to go bad. Is this enough information for anyone to give an educated guess? Do the symptoms I gave suggest a clogged CC? I can tell the muffler shop is scared to death of a hybrid and so they're not much help. He's saying he doesn't think replacing the catalytic converter is going to do the trick. I need to know what's going to get the car at least drivable again to further diagnose. Thanks much! Jeremy
When the CEL was blinking what codes came up? In my experience with a blinking CEL it is a multiple miss fire. That could be anything from ignition to vacuum leak. How fast would the P0420 come back after resetting? TomK
The p0420 would come back pretty quickly -- usually couldn't drive more than 40-50 miles without it coming back. My code reader would let me know when the systems would be ready for inspection and the catalyst would never go to "OK" before the CEL came back on. Usually when driving on the highway, the 0420 would show pending first -- when driving in the city, the EVAP codes would show pending first. I'm going to have to go back to my car and check the codes to see what else came up. The muffler shop said there were about 12 codes showing (don't know if he was exaggerating or not). When I first noticed the misfire and pulled over to get gas, I hooked up my code reader and at that time it was still showing the same four codes (0420, 0440, 0441, 0446). I didn't check it after I got back to my car several hours later and should have. I've got so many thoughts/theories in my head right now. I was driving through constant rain on Saturday and I have had a 1-2 second shuddering from my car when I first start it up in the morning after a lot of rain the day/night before as well. I believe that would likely have to do with the EVAP codes. But like I said, 1-2 seconds after startup and then everything is normal. It did have a similar episode a few months back where it really shuddered on startup (~5 seconds), hesitated on me down my neighborhood road, then as I accelerated on to a main road a lot of hesitation for a few moments before going back to normal again. Nothing ever like that again until this weekend when the shaking was so much I knew I shouldn't even drive it.
We would need to know the current DTC being logged. If the engine is missing so badly, that implies an ignition or fuel injection issue. It is possible that a clogged catalytic converter will substantially impair engine performance. So it wouldn't hurt to replace it, but the muffler shop tech may be correct in stating that is not likely to be the only significant issue that needs attention.
The shaking/shuddering combined with the blinking MIL give a strong suggestion of pretty bad misfiring, which is hard on everything (and by sending unburned fuel out the exhaust, it will eventually destroy your catalytic converter even if it's not dead yet). The official catalytic converter is not a cheap part (but it's not a ripoff either, it's very well made in stainless steel and lasts a crazy long time if not mistreated and you keep the HCAC valve lubed). So if it were me I'd start looking for the misfire causes and hope to maybe fix an underlying problem in time to save the converter. There was one code about the converter efficiency (determined from O2 readings, but those could be way off because of the misfiring). There were a lot of codes about the evap system. Fuel and ignition problems can cause misfiring but so could the wrong amount of air getting in, which a faulty evap system might do, so those codes might be worth following up. Evap systems are pretty strange beasts to diagnose - I'm happy I haven't had to. This writeup probably helps a lot though. -Chap
Or alternatively, as it seems the car detects evap leaks in part by looking at HC in exhaust, those codes could also be secondary to misfiring from another cause. Spark plugs are the easiest check, then injectors. If you turn out to have an injector issue I do have a set of 4 reconditioned and performance tested. Another PriusChatter needed a set in a hurry, so he bought an already reconditioned set, then we sent the old set for reconditioning after. They came out just fine. -Chap
The car reads 7 codes now -- the same four (0420, 0440, 0441, 0446) plus 3 misfire codes (0300, 0302, 0304). The muffler shop where I took it is not going to be of any help. Basically don't want to do work on hybrid cars. They think the misfire is from the normal sources (plugs, ignition coil, etc.). I think it has something to do with the previous 4 codes, just not sure whether catalyst or evap. Looking around online it seems a clogged cat CAN cause a misfire. Can't remember about the evap codes -- I'll have to check on that. Some good news is that starting it up today it seems like I can drive it somewhere else. Today it started up fine, idled smooth for about 5 secs., then starting idling rough. I'm thinking about getting it somewhere tomorrow that can do a smoke test to check the evap. Thanks for all the responses. Please if anyone has any more thoughts, do share. This is a great forum! Jeremy Also...does anyone know if a backpressure test can be done for the cat? The muffler shop told me they could not get to in front of the cat to do the test.
I think you should start by buying a set of four NGK or Denso iridium spark plugs (as specified in the owners manual) and replace the plugs. Also, clean and inspect the spark igniters. If you see any burn marks or cracking in the plastic body, or any corrosion on the electrical contacts, replace the igniter. Since you indicated that this problem came up after heavy rain, be alert for any moisture in the spark plug wells, especially cylinders 2 and 4 (cylinder 1 is closest to the passenger-side fender.) If you see evidence of water, that will show you that the cylinder head is being exposed to water. This can happen if rain water drips from the engine compartment cowl, down onto the engine. After you've replaced the spark plugs and inspected/reinstalled the igniters, disconnect the 12V battery for a few minutes, then reconnect. The purpose of that is to clear any existing DTC. After you've made the Prius READY, see if the engine runs smoothly. If it does not and the check engine light comes on again, see what the new DTC are. If you get the same P0302 and P0304 codes, try swapping the igniters for cylinders 1 and 2, disconnect the 12V battery again, then reconnect. See if P0302 has become P0301. If yes, then you will know the igniter that you just moved from cylinder 2 to cylinder 1 is defective. Do a similar swap for the igniters in cylinders 3 and 4 to see if P0304 becomes P0303.
That would be a cheap start. May try that tomorrow. I will say that the mechanic at the muffler shop who was originally thinking along those lines as well -- when I started it up he heard how rough the idling was and commented, "That doesn't sound good." That made me think he thought it was something more as well. He thought the engine was knocking enough to where it may be starved on oil, but oil was fine. Then it became, "You need to sell this car and buy you a gas car." So that shows you what I was working with.
It's as likely to go the other way ... misfires constantly pumping live gasoline down into the cat will eventually melt the honeycomb into a solid gob, and then you will have a clogged cat. BTDT (fortunately not in this car, but an older one where the cat was less money). I hope following Patrick's advice might get to the bottom of the misfire problem before that happens. -Chap
Update: The car was taken to another shop yesterday morning and I called in this morning. Sounds like they have been doing what was suggested above to get the car going again -- changed plugs, coils, etc. They say it is running better (have been able to take it on the highway), but still a misfire so they are going to do a check on injectors. I guess this is looking like a separate issue from my previous codes...
Sounds like it is on the mend. When you get a chance, read the sticky about ownership. It was also meant as a guide to the skills and tools to make NHW11 ownership more predictable and happy. You had already figured out the first mechanic 'had an agenda.' Knowledge is the best antidote to a dummy mechanic. Bob Wilson
