1999 T4R trouble code HELP PLEASE?

[SgtAbn]

I have a 1999 T4R Limited 3.4L V-6 and I am hoping someone can give me some guidance on how to solve the following check engine light codes please.
PO171- “Fuel System too lean bank 1” this code has been tripping my check engine light for some time, I’ve replaced the “bank 1” O2 sensor with a OEM one and I still have the same code that keeps popping up. I also replaced the spark plugs and wires. Every time I clear the code it comes back. A mechanic told me even though I am not getting a trouble code for the rear (bank 2) O2 sensor; sometimes you have to change them both at the same time?
PO120- “TPS “A” circuit problem”
PO420- “Cat efficiency below threshold bank 1”
The above 3 codes are what came up the last time I scanned them a couple of days ago. The local garage told me they recommended replacing both O2 sensors at the same time even though I already replaced the front (bank1) one and replacing the MAS (Mass Airflow Sensor) along with replacing the throttle position sensor all at the same time.

Below are the codes that chronically keep coming back at random but not every time:
PO401- “Exhaust gas recirculation flow insufficient”
PO100- “Mass or volume airflow circuit”
PO101- “Mass or volume airflow circuit range performance”
PO110- “Intake air temp sensor 1 circuit”

Anybody have this happen to a 3rd gen T4R? Any advice is appreciated…

 

[SgtAbn]

I cleaned the MAF, but my problem still exists..

 

[gamefreakgc]

Yikes, that's a lot all at once.

I would check for a vacuum leak with a can of MAF/carb cleaner and spray it on every hose end and your intake boot. Completely rule that out before going. You'll know if you find a leak since the idle will rise up as the cleaner finds its way into your engine. Might be the issue since I see a P0171 code on your list, a good place to start and very easy. Basically every major sensor in your engine and exhaust is tripping a code.

If not vacuum leak, I'd visually inspect the wiring to make sure nothing is severed or damaged. Has you ECU ever been contaminated with water?

Oh hey, look my file decided up upload. If you don't have the FSM this will help, hit CTRL+F and type in your code for quick searching.

 

[SgtAbn]

Thanks GameFreak, that was a good suggestion. I tried did a vacume test using the method you described and came up with nothing. So then I replaced the TPS (Throttle Position Sensor) and the MAS (Mass Air Flow Sensor) and so far my check engine light has not come back on..

 

[gamefreakgc]

I hope that's all it was then, those two sensors are pretty easy to replace. Time will tell if that cures all your problems you've had.

 

[ILRunner98]

How does one get an egr code for a 3.4L 5VZ? LOL

 

[gamefreakgc]

Some 5VZ-FE's I believe actually do have an EGR. Only the California emissions models, which seem to be pretty uncommon. They also have two catalytic converters.

My 5VZ-FE that's spent its whole life in California does not have an EGR though.

 

[TheDurk]

Some 5VZ-FE's I believe actually do have an EGR. Only the California emissions models, which seem to be pretty uncommon. They also have two catalytic converters.

My 5VZ-FE that's spent its whole life in California does not have an EGR though.

No 3G 4Runners with the 5VZ-FE had an EGR. I looked and the only 5VZ-FE's I could find were on OBDI vehicles, which means 1995 and earlier, such as the T100.

For those that have wondered what those funky dead-end line fittings on top of the V6 throttle body do, that's where the EGR ties in, if there is one.

 

[gamefreakgc]

No 3G 4Runners with the 5VZ-FE had an EGR. I looked and the only 5VZ-FE's I could find were on OBDI vehicles, which means 1995 and earlier, such as the T100.

For those that have wondered what those funky dead-end line fittings on top of the V6 throttle body do, that's where the EGR ties in, if there is one.

Ahh, that would explain it. I've heard a couple of people were unable to install the URD/TRD 7th injector kits because it had an EGR, but they must have either had T100's or a donor engine.