i finally got around to having my o2 sensor pre cat replaced today. cleared the cel, and been driving around, everything's groovy. tonight i stop at a red light and the cel comes back on. something about the catalytic converter now. but the thing i don't get is that it is getting pretty good gas mileage consistently. always 18.5 in city and 19+ on highway. do you think its worth getting some work done to the cat converter or should i just try to overlook the cel light? or pull the dang cel bulb?? 97 sr5 auto 3.4 4x4 with 275+K. thanks in advance

 

If it's P0420, then get yourself a replacement high flow cat.
A quick search on that code will yeild good info for replacement cats.

 

Go to toyota dealership and get it scan for code(s). If it's P0172 or P0171, I can't remember, that could be a MAF. Good luck.

 

What code are you getting?

If it is your post cat O2 sensor, you can get another sensor... but that's spendy.

There is a cheap box that can be made that will feed the ECM the correct signal for this 2nd O2 and eliminate your code forever. Since the 2nd O2 only checks the cats performance, the always correct signal isn't cheating or causing the motor to run incorrectly based on false information.

I built this box for under $10 to get rid of a pesky PO420 that kept popping my CEL after my swap.

Details can be found towards the bottom of this page:
https://www.yotatech.com/forums/f160...5/index10.html

 

Good work around on the rear O2 sensor! Basically it fools the ECU into thinking the cats are working amazingly well (ie it shows very lean.....but since the rear O2 only checks the condition of the cat, you don't suffer any fuel/driveability problems either) You wouldn't want to bypass the heater on the O2 because 12w is alot of power to dissipate so as long as your rear O2's heater circuit works, you should leave it connected. You also can't just disconnect it because the ECU will also throw a code for that.

I believe someone was also able to run 2 high flow cats inline and solve the P0420 code as well.
A single high flow cat is not enough to lower the emissions to what the ECU on a cali spec vehicle expects to see in operation.

 

great info guys. i appreciate it. i'm going to give it another look this weekend.

 

well that would be just great, b/c my maf is the "old" type. i took a picture and posted it on here and evidently is isn't the normal one that is on most 97 SR5 4x4's. I looked it over, and it's not the type that you can take apart to clean (found out after i bought the cleaning fluid for it). So i'm stuck if its maf.

 

You can clean those 96-98 MAF types too.

Here's a good thread on that:
http://4runners.org/writeups/throttle/index.html

http://www.ultimateyota.com/index.ph...6&topic=1033.0

 

that is a great thread MTL! you the man! thanks

 

Funny, I'm dealing with the same thing right now. Had a code for the front 02 sensor (P0130?), which I knew was going on the fritz a few years ago, but the CEL had not come on since then. Anyway, changed out the front 02, drove about 75 miles and CEL came on again. This time P0171. Cleaned the MAF (again) as well as cleaned and adjusted the intake tube & clamps. CEL came on again. Haven't checked the code yet this time. Annoying.

 

I've had the P0420 in the last few months. I've cleaned the MAF - twice. Replaced plugs (it was time) as well as other maintenance. The light would return pretty regularly. I went ahead and purchased new sensors (120k miles) - probably time for the front one anyway. Well, the CEL hasn't come back on since. I did not replace the sensors yet... waiting for the CEL to return.. I think my truck has a mind of its own!!

 

111db... if you make it out this Sunday I'll bring my OBDII scanner which connect to the laptop. Might get some more information of your code.

The catch is I saved some pennies and didn't get a universal scanner, but one for the protocol of my '96. I can't tell for sure, but there is a 50/50 chance Toyota changed the protocol in '97 and my scanner won't read you vehicle... it might be worth a shot though.

 

Cool, I'd like to see if it works. I just haven't had time to go through all the FSM troubleshooting steps for it yet.

 

If you can hook up to your 96 then it will work on a 97 for sure. Toyota (along with everyone else) switched to the OBD II standard in the 1996 model year. Now within OBD II there are 3 basic protocols: SAE J1850 VPW, ISO 9141 and SAE J1850 PWM, but to the best of my knowledge, Toyota only uses the ISO 9141 protocol. So your scanner, even if it only supported 1 Toyota protocol, should be enough to read all model years 1996 and newer. Only a newer reader will also have the CAN protocol support (which isn't on any Toyota trucks until 2005), but that's a whole different can of worms.

 

just had the code cleared at autozone. sure enough it is a P0420 that keeps tripping the cel. given that, do you think that cleaning the maf and intake would be a waste of time (in terms of clearing up the cel), and i should focus my attention on getting a high flow cat?

 

i just went ahead and cleaned the maf and the throttle body. you guys should have seen the inside of that beast with my mileage! the black hole for sure. i didn't have a camera with me or i would have posted pics. i hope to see some improvements on throttle response soon.

 

go for the high flow cats, theyre a lot cheaper than oem cats anyway arent they? my buddy has the same code on his mustang and thats what he was told to do is to get high flow cats...

 

What CATs would anyone recommend with a truck that has Cali emissions?

 

Update: Swapped airbox and installed a new 99-02 MAF. Cleared codes. CEL came on at the stoplight again, this time P0171, P0130, P0133.

I have a brand new URD front 02 Sensor and new OEM MAF.
Frustrating.

 

no joke jon. i was sick of that light on my white one so i got rid of it (it was up there in miles anyway). i'm pretty sure mine was cat related.