Please advise for stall Problem Codes P0172 & P0175 - banks to rich?
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2001LC
SILVER Star
Fuel pressure regulator (FRP) can be affected by temperature, this makes detecting difficult. This is often indicated by varying MPG. Sitting for prolonged periods of time and rust (from water in fuel) can develop in or on needles FPR and fuel injectors.
They are very easy to replace and and cost ~$100. The little (4" long) fuel hose coming off it is $20 OEM.
While checking for vacuum leaks don't forget, duel line coming off VAN pump (power steering pump)
They are very easy to replace and and cost ~$100. The little (4" long) fuel hose coming off it is $20 OEM.
While checking for vacuum leaks don't forget, duel line coming off VAN pump (power steering pump)
2001LC
SILVER Star
Check also for vacuum leaks at PCV valve & grommet and both hoses.
98-02 PCV valve fits in a grommet seen here in background
98-02 PCV valve fits in a grommet seen here in background
How I interpret your readings is that when your truck is running normal that is when it is running rich and this is your pending fault code. When the fault is present you are running lean and the ECM is trying to pump fuel in. So either you are running out of fuel or a sensor is saying you are lean. Your fuel trims prove this, your LTFT are rich whilst your STFT are lean when your fault is present. It could be as simple as your fuel pump cutting out, your FPR playing up or MAF sensor etc. What I can’t get my head around is your O2 sensor reading all being 0v. This why I asked to check ECM connectors, but still confusing. Unless it is internal to ECM, Or it is your code reader..
- Thread starter
- #25
My check engine light has never came on. The only reason I was able to pull these codes was because it started stalling in my driveway. So I was able to hook up my code reader quickly.
99% of the time, the LX 470 runs perfectly. Then all of a sudden it stalls the other 1%. After 1 - 5 times restarting (over a period of 1 - 30 seconds total) it will continue to stall, it will continue to restart and then all of sudden on some random restart it run perfectly again for another 100+ miles plus.
This is why the Toyota dealership says they can not recreate the problem.
99% of the time, the LX 470 runs perfectly. Then all of a sudden it stalls the other 1%. After 1 - 5 times restarting (over a period of 1 - 30 seconds total) it will continue to stall, it will continue to restart and then all of sudden on some random restart it run perfectly again for another 100+ miles plus.
This is why the Toyota dealership says they can not recreate the problem.
The fault codes are pending, this is because it is seeing a rich mixture but not high enough or for not long enough, this is on your LTFT that they are a negative number when your running good so there is some compensation going on.
I will ignore your Code Reader readings and guess Fuel pump or fuel delivery issue.
Drive around with your rear seat up and expose the pump, put a test light on or multimeter and see if you can find any abnormalities. Pump cuts out, Pump noisy, lose feed or ground etc. Remove the pump and inspect fuel condition as in water in the tank or other contaminant.
I will ignore your Code Reader readings and guess Fuel pump or fuel delivery issue.
Drive around with your rear seat up and expose the pump, put a test light on or multimeter and see if you can find any abnormalities. Pump cuts out, Pump noisy, lose feed or ground etc. Remove the pump and inspect fuel condition as in water in the tank or other contaminant.
Keep an eye on the brightness of your test lamp or voltage on your multimeter. If you put a test lamp across the battery first then you will know how bright it is expected to be. This will check for any voltage drop from the relay, wiring etc.
- Thread starter
- #28
I would like to thank everyone for your suggestions & I think my dealership might have found my problem.
They kept my 2001 LX for about 2 weeks & it finally stalled on them. They said the Mass Air Flow sensor was slow to respond.
They replaced it with a new MAF & I have driven it some this weekend. So far, it seems to be doing great! A little more power & not shifting gears as often.
I wanted to update this thread in case it helps anyone in the future.
They kept my 2001 LX for about 2 weeks & it finally stalled on them. They said the Mass Air Flow sensor was slow to respond.
They replaced it with a new MAF & I have driven it some this weekend. So far, it seems to be doing great! A little more power & not shifting gears as often.
I wanted to update this thread in case it helps anyone in the future.
2001LC
SILVER Star
Good info, thanks you for updating.
- Thread starter
- #30
I just wanted to update this thread for anyone in the future with the same problem.
It has been roughly 6 months since my dealer changed out my MAF and it hasn't at all in the past 6 months! It drives just like a brand new SUV!
It has been roughly 6 months since my dealer changed out my MAF and it hasn't at all in the past 6 months! It drives just like a brand new SUV!
- Thread starter
- #31
Another update: After a year, the 2001 LX is still driving like it is brand new! Safe to say now that the slow to respond MAF sensor was my problem.
THANK YOU for providing a detailed description of the issue along with the fix and updates. I just had the same thing happening to me on my 02 LX, the book gives a host of things to check for but based on your experience I just started with the MAF and all is well so far. You saved me from a potentially long and painful diagnosis due to the inconsistency of it acting up. Thanks!
- Thread starter
- #33
I am glad that I could help!
Mine has been perfect after putting in a new Toyota brand MAF (Btw, I have heard bad stories about people using part's houses brand MAF so I would only buy a MAF from Toyota.)
I never trust electronics to the house brand, only OE. I've got one on order, in the mean time I did try to clean the one I have now. It's original with 240k on it, definitely had never been cleaned/replaced. It's a little better but still acting up. Hopefully the new MAF settles the issue, otherwise I'll keep working down the list of probables.
Howd it go?
New MAF solved the problem. I sold the LX a while back but I never had issues with it after the MAF.
Thanks for thr quick response!
I’ll revive this old thread to provide another data point. I got P0172 and P0175 on my 06 LC (230k mi), except I didn’t have any stalling problems for 3-4 months. In fact the engine ran perfectly despite getting these codes. I’d clean the MAF and clear the codes, they’d pop back up in 50 miles or so. Repeat for months.
It finally stalled once about 4 months after getting the codes initially, and started right back up and drove as if it never happened, smooth idle, drove fine. New OEM MAF installed, 150+ miles later no resurgence of codes or stalling.
It finally stalled once about 4 months after getting the codes initially, and started right back up and drove as if it never happened, smooth idle, drove fine. New OEM MAF installed, 150+ miles later no resurgence of codes or stalling.
I've been chasing down my stalling issue for like 2 years now. It happens about once every 3-4 months so it's impossible to recreate and never gave any codes. I just got these P0172 and P0175 codes today and it led me to this thread, which I'd not found previously to my knowledge. I replaced my MAF about 5 years ago with a unit from Partsouq, but I'm about to replace it again and cross my fingers with an updated part number version from a US supplier. Please work...
How you're replacing with OEM MAF. Good luck.
Also why don't all of you check what is your fuel pump pressure sending out. It might help your narrow down your problems.
You can jerry rig a part that would get this info for you.
