New(ish) Member with Codes

Hello out there, this is my first post on TW but have been enjoying and learning from this site for years. It’s been the first place i go to trouble shoot or research most anything for my truck. Kudos and thanks to all of you who have shared your wealth of knowledge and experiences. For someone like me that doesn’t have lots of mechanical experience or knowledge, but is motivated to research and not afraid to get a greasy, this site and it’s members have help me more than i can accurately describe.
All that being said, my ‘03 SR5 3.4L V6 has reached 175k now and is showing more signs of its age. It’s mainly my work vehicle and doesn’t look to pretty but has always fired right up and ran with no problems. Not the case anymore. Did the plugs & wires , fixed a vacuum leak at the air box, a week later it started spitting codes at me and runs with a slightly rough idle until it warms up and is driven a half mile or so. My boss told me he thinks that CAT CONVRTR is getting plugged but dealership parts guy told me that’s almost never the case, cat is designed to last a much more than 175k. Although my truck does idle a lot, especially in the winter. Ran some CATACLEAN through the system, cleaned the MAF , and a couple hundred miles later the check engine light turned off and seemed to have solved the problem. Also started running 91 octane non-ethanol fuel and it seemed to like that. Light has came back on and turned off twice now and yesterday going up a steep hill it started chugging a bit and almost acting like it was running out of fuel. Has a half tank of gas. On the way home, no issues.
Have ran a scan yet today, bought a BlueDriver obd2 scanner, but the codes i’ve seen previously are : PO300 - random/multi cyl misfire, PO303 & PO304, PO102 - MAF/VAF low input, PO113 - IAT sensor high input, PO420 - Cat. Conv. Sys. Bank 1 efficiency below threshold, PO446 - EVAP system vent control circuit malfunction, also have some CO ABS codes but i know what that stuff is from.
So, I’ve search this and other sites and found a broad spectrum of suggestions and solutions to a wide variety of problems related to some of these codes. The problem is there is a limited budget for me to get this figured out and running out of time before the cold weather really sets in. Trying to avoid paying $95/hr to figure this out, knowing that i can do the work myself once i know what the real problem is. Can’t afford to start throwing parts at it.
Thank you for all the wisdom and info you’ve shared that has helped me in the past, if there are any offerings of advice and/or wisdom for my most recent and most complicated case of busted taco syndrome i will again be indebted those wiser and more mechanically inclined than i may ever be.
Sincerely, Chuck D.

 

@BngdUpTaco’03

You'll get a lot less info you can't use if you go ahead and list some more maintenance history, like have you ever changed fuel filter, do you ever run injector cleaner, fuel pump ever been replaced or pressure tested, throttle body been cleaned, O2 sensors still original...? At 175,000 a lot of routine maintenance is overdue if it hasn't been done.

 

You need the specific error codes that the truck is throwing now. Disconnect battery or pull efi fuse under the hood to clear existing codes. Then as they come up as you drive, relay them here.

 

Ok thanks Wsdir. Cruiser, didn’t get the other home projects finished in time to check the current codes today but will be on that first thing in the a.m.
As far as the maintenance that’s been done, the schedule was followed totally until about 75k. Gotta check to see the details of that. But don’t recall a fuel filter ever being since i quit going to the dealership for everything. A week prior to the issues starting i ran a bottle of dry gas with injector cleaner, occasionally would use some of that Lucas product that comes in the little bottle, fuel pump never replaced or pressure tested, haven’t cleaned throttle body yet, downstream O2 sensor was replaced at approx 125k, always use Mobil 1 oil and every other change substitute in some Marvel Mystery. ... can’t think of any other useful info to mention. Though there’s gotta be something I’m missing.

 

Which plugs & which wires did you replace with? If Denso & NGK , then you need to look at coil packs, fuel injectors, fuel filter, fuel pump.

 

Good question about the plugs and wires. Had the mechanic do it while it was in getting the a/c recharged. He works on Tacomas all the time so I’d be surprised if he wasn’t aware of how finicky they can be. Did check the codes again this wknd and the PO303 and PO446 were back as confirmed and the PO442 was back as pending. Time to swap around the coil packs i guess and see if the misfire code changes cylinders. Had this truck since it was delivered from the factory and had no serious or challenging issues. Oil changes, timing belt, air filters, fluid film. The basics is all its ever asked for, i suppose its earned its keep and the right to make further demands.

 

Ok, P303 is obviously misfire in cylinder 3. Yes , switch coil packs and reset codes. if it comes up 303 again good chance it is bad injector. P0446, you should inspect gas cap. If that looks fine, it could be purge valve on evap system. The P0442 means leak in evap system which I think in turn can set a p0446 code too if I am correct. Also, clean that throttle body and clean your mass air flow sensor. Have you ever replaced your upstream sensor?

 

If your not sure on fuel filter, get that changed too. I did fuel filter, plugs, wires, cleaned throttle body and Maf and replace both o2 sensors and the truck runs like it did when I bought it new in 03. But your po446, po442 is definitely issue with evap system.

 

Ok. Thanks djohn, and all who have chimed in. Feel much better already having some educated opinions on where to start and with which parts. Turns out our mechanic didn’t use the recommended wires. Kinda surprised considering his rep and our previous experience with him. Had dealership do the timing belt a while back and they said ‘we almost never need to change plug wires, they rarely wear out’ . Phooey on me for falling for the service dept b.s. The parts guys there are great but service reps are. ... well, you know.
Can’t help but wonder about that charcoal canister as well. I certainly over filled more than once prior to knowing about the canister and what its job was. Looks like i’ll be creeping up on $1000 even without buying a Toyota cat.
Hope it doesn’t turn out to be that .

 

Forgot to mention on your P0420 code. I had it on mine and I believe it was the rear o2 sensor. It had a hole around the base of the port, nice little exhaust leak. I would check your sensor when running truck to see if you have any leaking around it. Another reason I ruled out cats, i used a infrared temp gun on the cats when truck warmed up. Make sure you point it on cats and not heat shields. The rear of the cats should be 100 degrees or so hotter then the front of cats. Mine checked out fine. I ended up getting a walker cat back system and installed new oxygen sensor.

I would first get the misfire codes solved and change fuel filter if never done. The chugging up hill could be from misfires. But if you solve them and change fuel filter, use your obd2 scanner and take a look at your fuel trims while truck is running. (STFT) for short & (LTFT) for long. you will see + & - negative readings. both long & short should be close to 0 as possible but -10 to +10 is the range. Anything higher or lower on either is saying there is a issue. High positive points to vacuum leak and low negative points to low fuel pressure or bad MAF. Good luck!

 

Thanks again dj! All the info is a huge help. Since you mentioned it i suppose i’ll Post up all the live data i got from the first time i used the obd2 scanner. Fuel trims seem ok but maybe it’ll shed some light for one of you that’s smarter than i am.

MAF rate = 0.5 lb/min ; 14.5-16.5 degree cyl#1 timing advance ; STFT bank 1 = 00-1.6% ;
LTFT bank 1 = -0.8%
Also got some equivalence ratios but i have no idea what they mean.
0.9996-1.0 wide range O2 - bank 1 - sensor 1
3.29-3.3 volts - wide range 02 - b1 - s1

99.2% O2 - bank 1 - sensor 2
0.720 volts O2 - b1 -s2

I get the gist of the fuel trim stuff but the O2 sensor numbers are leagues over my head and understanding.

Again, thanks to all of you for your help!
Without TW’s member’s and their wisdom =
With TW member’s sharing their knowledge =

 

The most important thing to remember !!

It is not just the sensor or part it is the complete circuit wires and ECM.

Seems a bunch of problems all at once .

Best of Luck

 

Fuel trims look normal. I assume that was at idle? Should get a reading too under load. About 2,500 rpms. The bank 1 sensor is your air/fuel sensor in front of your first cat. Bank 2 behind your last cat before muffler. I don't remember the normal readings for those. I will plug my scanner in and get a reading on them to compare to yours. Ok, did a scan. your numbers for MAF, B1 , B2 all are similar to mine. So, misfires and evap codes should fix your issues. Your welcome!!!

 

ECM ... ?? Wyoming, don’t like the sounds (Ching Ching) of that!
Hoping you mean it all works together and not that its all got some issues. At some point i’ve Gotta put a cap on the budget for this 15+ yr old vehicle.
Yes, Thanks djohn!! If my info is in the same ballpark as yours is i’m Gonna ass’u’me that my cat and O2 sensors aren’t in any dire need of being replaced. Which is a big relief considering the cost of a quality cat and the corroded nuts on the O2s.
For the evap stuff i’m Gonna replace the valves and hoses under the hood and cross my fingers that i don’t need to do the charcoal canister.
For the misfire and rough idle stuff i’m Starting with a fuel filter and throttle body cleansing, already swapped the #3 & 5 coil packs and waiting for enough cycles for codes to show up. Mechanic did use NGK plugs, but wires are not Denso or NGK. Hoping thru elimination i solve it without getting into injectors and compression issues. Don’t know i’ve got the time or the tools for that.

 

Let me correct my wording on the sensors. Bank 1 is the passenger side and the sensors are bank 1, sensor 1 & bank 1, sensor 2. Sensor 1 is air/fuel sensor sensor in front of your first cat and sensor 2 is your oxygen sensor behind your last cat. I will say, my PO420 was fixed by replacing the oxygen sensor that had a exhaust leak around it. I think it's important to check the temps of your cats like I mentioned in post above. Some tips on saving money on anything you need. Do you shop Amazon, Ebay ? What about a local Advance auto parts? The key with Advance is to have a online account and most times on Fri, Sat, Sun you can get 25% discounts buying online then picking up in store. I got both sensors on Ebay. You have to watch though. Many selling these Denso air/fuel sensors for 39.99 but they are knock offs and don't work. I was able to find a seller that had a true Denso air/fuel sensor and got it for $80 v.s $114 on Amazon and $179 at advance. I think the seller of the air/fuel sensor has some left. I got the walker cat back system through advance for around $135 after the 25% off. That included the intermediate pipe too that has the port for o2 sensor. Rock auto was cheaper but the shipping took it to about $180

 

Plug wires should be fine. Denso, NGK plugs...perfect! The sensors are the other area to stick to Denso

 

Crossing my fingers that i don’t have to buy any O2 sensors, but if so i will certainly stick with the Denso/Toyota parts. Found a small exhaust leak south of the cats and o2s , gonna seal it up and hope it makes a difference. Also gonna take the advice and put temp gun on the cats. Hope i can get a good angle on the top of the upstream cat. No heat shield on the downstream one. If i have to replace the upstream cat i’ll probably go with the Bosal, it’s a bit pricey ($400ish) but if it gets me 20 or 30k more miles than the MagnaFlow i’ll go for it. I’ve probably over researched but from what others are saying the economy priced parts are gonna last about 2-3 yrs and then need to be done again.
Did get the evap valves under the hood changed. Next is the fuel filter, as soon as i can get a 19mm flare wrench. Why Toyota, why must you use a size that is so uncommon and isn’t readily available at the parts or hardware stores. Probably just order it, what’s another 20 bucks at this point.
Been 2 days and still no lights or codes since i switched the coil packs around. Don’t know if that’s good or bad, time will tell i guess.

 

Well, the PO303 code is back. Checked the plug and all seems ok there. Next step is the injector i think. A bit out of my comfort zone, i guess its time to broaden it.

 

OK, do you have a multimeter you can test with? https://youtu.be/yFv5IWdANGs

 

Or you can just go ahead and change it out. Doesn't really look like a difficult job.
https://youtu.be/EHhYTQYMzl4