[Crackhour]

My first ever Toyota. 03 Highlander 3.0L 192k miles...OUCH!!! For its age and mileage it looks and rides great. But surely you can't buy a vehicle this old with this many miles and not have a code or two. I bought this it because I was in a situation where I needed a car asap to get to work. I uploaded a diagnostic report from OBDfusion. I'm definitely willing to invest a few dollars to keep this car running but not going to go all out. Any DIYers out there willing to chime in some advice on what I have here. Much appreciated.

 

[underthehood51]

Pay special heed to oil consumption if the engine has not had a steady diet of quality synthetic oils in it's life or improperly followed change intervals. Timing belt, water pump, front crankshaft and cam seals along with tensioner and idler. Maybe spark plugs. The 3.0 is a sweet engine but problematic for sludge and oil burning. Look for my posts re oil consumption and how I "cured" it.

 

[Crackhour]

Duly noted. Thanks for the heads up. At moment dealing with the P0420 single code.

 

[C R]

If you have no exhaust leaks, Probably is the Bank 1 cat, which is against the firewall. However, the monitor completed. So it looks marginal. If you just need to get past smog, you might be able to replace the upstream sensor and get it to clear after a drive cycle. For this, use the Denso part. Aftermarket parts usually give marginal performance to start with. There are a few less likely things to check too. Fuel trim is dialed back so the sensor sees a rich mix, which could be the sensor. You can try replacing plugs, cleaning the MAF and PCV, and checking the ECT sensor and air filter.
If the sensor doesn’t clear it long enough to pass smog then you probably need to replace the cat on that side.

I see that the evap monitor did not complete. So you have a problem there too but has not set a code yet.

Do you need to pass a smog check or did you just want to fix it? What state?

 

[Crackhour]

Western PA. Like I said it rides nice. I’ll put some money into repairs just don’t want to go all out is all. What you mentioned so far seem to be a DIY. I have a buddy with a garage. We’ll replace some of the aforementioned parts you mentioned. Stickers good til October. I’ll likely have that cat replaced by then. Hey I appreciate your honest feedback. You guys are great.

 

[Mgeorge]

If replacing the cat is not in the budget or the value of the car doesn't justify an expensive cat replacement try using O2 sensor extenders. They are easily available on amazon and cost only about $10 to $20. They won't fix the po420 code but will hide it from the computer and keep that light off. I've had mine in for over 2 years and they work great. You will need one straight one and one right angle one for clearance against the firewall on the rear o2 sensor.
Of course, try some of the previously mentioned maintenance items first to make sure.

 

[Crackhour]

That’s good advice. I’ll look into that. Not due for inspection till October so the Cat can wait unless I’m mistaken. I’m already in the planning stages of replacing oxygen sensors on the Bank 1. PCV. spark plugs and likely fuel injectors since I’ll be down in there anyway. I think there’s a knock sensor down there also

 

[Mgeorge]

If you're looking to hold on to some of your money, try just replacing the one upstream A\F sensor as C R suggests along with those other things you've mentioned. I wouldn't mess with the injectors though, I really haven't heard of this engine having problems with them. Mine have 272,000 miles on them and no issues, btw. The knock sensor is under the lower intake manifold. Change it if you want but that's extra work and more money. If you do change it get the harness too.
Hayabusafalcon has a good writeup on replacing sparkplugs without removing the intake manifold at all if you're interested, I think it's in the sticky section.

 

[C R]

If replacing the cat is not in the budget or the value of the car doesn't justify an expensive cat replacement try using O2 sensor extenders. They are easily available on amazon and cost only about $10 to $20. They won't fix the po420 code but will hide it from the computer and keep that light off. I've had mine in for over 2 years and they work great. You will need one straight one and one right angle one for clearance against the firewall on the rear o2 sensor.
Of course, try some of the previously mentioned maintenance items first to make sure.

Just be aware that it would be considered emissions tampering to use the extenders. I’m not sure what the penalties would be in PA if the smog guy spotted it. A lot of states don’t take it well.
A cat efficiency code does not indicate a condition which will damage the engine UNLESS it indicates a clogged cat that is generating back pressure, which can cause poor performance and damage in some engines. There is a vacuum gauge screening test to check it. It is in the Haynes manual and on Youtube

 

[Crackhour]

I gave the thought to fuel injectors since I’d be down there. But i hear your point. My diagnostic is showing rich but no code

 

[Crackhour]

Just to be clear. The A/F sensor (upstream) I’m looking for is the one directly in front of engine across from radiator. You pop the hood open looking down directly at it?

 

[C R]

Double check your code, but I believe it was bank 1. Unfortunately Bank 1 is at the back. Not as easy.

 

[Crackhour]

It’s bank 1 but two sensors are on bank 1. I thought b1s1 be upstream and b1s2 be downstream behind the cat. Confusing

 

[Crackhour]

I found it. Just a reminder this my first ever Toyota. And truth told, seems a lot easier to work on than a BMW

 

[C R]

There are two bank 1 sensors. Upstream B1S1 on the manifold before the bank 1 cat and downstream B1S2 after the cat.

 

[Crackhour]

Thanks. I found it. Online pricing the sensor. Autozone have it for $187. 234-9009 part #

 

[Crackhour]

I haven't done anything with that p0240 code yet. I still have time til the October state inspection plus this Covid-19 tightened up my pockets so to speak. In the meantime I been fiddling around underneath looking along that exhaust pipe. Put some CRC on the MAF. All the hoses are fine and tight between the air box and throttle body.

 

[Hoosier Daddy]

I just recently adopted an '03 Limited HL with very similar miles to yours, Crackhour, so I can relate to your post. Paid $3k for the car, and so far have put about $600 into it, with timing belt, all fluids, various cosmetic issues, small repairs, drive belts, thermostat, new stereo, etc. Still need to fix an exhaust leak between the rear manifold and cat, but that will be cheap. For less than $3700, this car should turn out to be rock solid, reliable, and looking good.

I just pulled my bank 1 upstream sensor yesterday when investigating my exhaust leak. Not too hard with the car on ramps, but it did require the special O2 sensor socket set that the auto part stores loan out.

Crackhour, I'm wondering why you are looking at plugs, knock sensors, and injectors, if your goal is just to drive it on the cheap. All those items are expensive and require a lot of work (and throw in extra $$ for intake gasket and knock sensor wiring to do it right), so I'm not sure I'd go there unless at least one of them definitely needed to be done. Do you know if/when plugs were done previously? They should be due every 120k miles.

FWIW, my fuel trims look similar to yours, IIRC.

 

[Crackhour]

This car definitely rides nice for the mileage. Very quiet. As far as what's been done to it before I bought it no idea except the oil was changed 2100 or miles ago. I did replace the dinosaur with my Kenwood from a previous car. Now regarding that P0420 code. That cat is part of a Y shape exhaust down there. I priced them and the prices range cheap to expensive. Getting the flanges cut out and having a bridge welded in is a cheap fix BUT would if the cat really is bad, ya know?

 

[Hoosier Daddy]

If it were me, I'd do the Eastern Catalytic or Walker cat/Ypipe from Rock Auto, for about $250.

Between a Carfax and registering on Toyota Owners (link - Welcome to Toyota Owners ) you can probably find a great deal of your car's service history.