P0171 help
Thread Starter
Pit Crew
Joined: Jun 2021
Posts: 138
Likes: 32
From: FL
P0171 help
hey all, work I've done recently:
-Replaced both VVT solenoids.
-Replaced the wire harness on bank 2 (the connector piece was covered in oil, that's now on my to do list to find the issue)
-Replaced all 8 spark plugs
-Replaced ignition coil on spark plug 2
When I replaced the wire harness (for the passenger side VVT solenoid), it solved my P1354 code on bank 2. After that I was running with no codes at all. Engine running good. Now tonight I drive home, and as soon as I pull in the engine light comes back on. P0171. P0171 is bank 1, I have not touched bank 1 other than to replace the solenoid recently.
Why would P0171 (bank 1 issue) only start after I fixed the issue with bank 2? Never seen this code before
My next step is replacing the MAF sensor, just waiting for it to arrive. What else should I look out for?
Additional relevant info- car is in limp mode. Doesn't really rev above 3000 rpms. I will note though once I fixed P1354 my car has been running so much smoother, and the engine feels like it's getting more power to it when I accelerate. Just still not going past 3000 rpm
thanks for any advice
-Replaced both VVT solenoids.
-Replaced the wire harness on bank 2 (the connector piece was covered in oil, that's now on my to do list to find the issue)
-Replaced all 8 spark plugs
-Replaced ignition coil on spark plug 2
When I replaced the wire harness (for the passenger side VVT solenoid), it solved my P1354 code on bank 2. After that I was running with no codes at all. Engine running good. Now tonight I drive home, and as soon as I pull in the engine light comes back on. P0171. P0171 is bank 1, I have not touched bank 1 other than to replace the solenoid recently.
Why would P0171 (bank 1 issue) only start after I fixed the issue with bank 2? Never seen this code before
My next step is replacing the MAF sensor, just waiting for it to arrive. What else should I look out for?
Additional relevant info- car is in limp mode. Doesn't really rev above 3000 rpms. I will note though once I fixed P1354 my car has been running so much smoother, and the engine feels like it's getting more power to it when I accelerate. Just still not going past 3000 rpm
thanks for any advice
Last edited by teaa; Dec 5, 2021 at 09:56 PM.
Instructor
Joined: Dec 2015
Posts: 878
Likes: 232
From: Arizona
The new MAF may fix it. That code is for lean mixture on bank 1 and has nothing to do with the vvt solenoids. Could also be a vacuum leak or a dead fuel injector. That code won't put the engine in limp mode so you may have other issues as well.
Pole Position
Joined: Sep 2018
Posts: 265
Likes: 72
From: New South Wales
P0171 is too lean bank 1
The computer thinks it ir running too lean according to how much air it 'thinks' is getting into the engine.
Too lean can be cause by a few things...
- Maf (is the sensor reading correctly? I note you have a new one on the way... Is it from a good source like a legit toyota parts supplier or a denso from Rock Auto? Ie not ebay fakes)
- Air leaks from old hard brittle vacuum hoses (this is very likely - when was the last time these were refreshed, including pcv and grommet)
- O2 sensor 1 reading strangely lean (need to see the graph for behaviour)
- Air leak in the exhaust between engine and O2 sensor (unlikely but you may hear it)
- Blocked injectors on one side (unlikely)
Start with the first 2 on the list. Maf and vacuum hoses. It's remarkable how often it is one or both of those things. If it's not those two then lets get a data from the engine to see whats happening to the sensors
The computer thinks it ir running too lean according to how much air it 'thinks' is getting into the engine.
Too lean can be cause by a few things...
- Maf (is the sensor reading correctly? I note you have a new one on the way... Is it from a good source like a legit toyota parts supplier or a denso from Rock Auto? Ie not ebay fakes)
- Air leaks from old hard brittle vacuum hoses (this is very likely - when was the last time these were refreshed, including pcv and grommet)
- O2 sensor 1 reading strangely lean (need to see the graph for behaviour)
- Air leak in the exhaust between engine and O2 sensor (unlikely but you may hear it)
- Blocked injectors on one side (unlikely)
Start with the first 2 on the list. Maf and vacuum hoses. It's remarkable how often it is one or both of those things. If it's not those two then lets get a data from the engine to see whats happening to the sensors
Thread Starter
Pit Crew
Joined: Jun 2021
Posts: 138
Likes: 32
From: FL
P0171 is too lean bank 1
The computer thinks it ir running too lean according to how much air it 'thinks' is getting into the engine.
Too lean can be cause by a few things...
- Maf (is the sensor reading correctly? I note you have a new one on the way... Is it from a good source like a legit toyota parts supplier or a denso from Rock Auto? Ie not ebay fakes)
- Air leaks from old hard brittle vacuum hoses (this is very likely - when was the last time these were refreshed, including pcv and grommet)
- O2 sensor 1 reading strangely lean (need to see the graph for behaviour)
- Air leak in the exhaust between engine and O2 sensor (unlikely but you may hear it)
- Blocked injectors on one side (unlikely)
Start with the first 2 on the list. Maf and vacuum hoses. It's remarkable how often it is one or both of those things. If it's not those two then lets get a data from the engine to see whats happening to the sensors
The computer thinks it ir running too lean according to how much air it 'thinks' is getting into the engine.
Too lean can be cause by a few things...
- Maf (is the sensor reading correctly? I note you have a new one on the way... Is it from a good source like a legit toyota parts supplier or a denso from Rock Auto? Ie not ebay fakes)
- Air leaks from old hard brittle vacuum hoses (this is very likely - when was the last time these were refreshed, including pcv and grommet)
- O2 sensor 1 reading strangely lean (need to see the graph for behaviour)
- Air leak in the exhaust between engine and O2 sensor (unlikely but you may hear it)
- Blocked injectors on one side (unlikely)
Start with the first 2 on the list. Maf and vacuum hoses. It's remarkable how often it is one or both of those things. If it's not those two then lets get a data from the engine to see whats happening to the sensors
I have already had a few wires and hoses replaced in the engine bay. There were some cracked ones here and there. From what i can see all visible hoses now are fine. Im not sure about ones deeper in the engine.
I’m not sure when the pcv was replaced last. Will do that next as well.
thanks for this, its useful info. I’ll get back with more after the maf replacement
Thread Starter
Pit Crew
Joined: Jun 2021
Posts: 138
Likes: 32
From: FL
Originally Posted by 911LE;[url=tel:11176882
11176882]The new MAF may fix it. That code is for lean mixture on bank 1 and has nothing to do with the vvt solenoids. Could also be a vacuum leak or a dead fuel injector. That code won't put the engine in limp mode so you may have other issues as well.
hopefully I can catch a break with the MAF sensor
Thread Starter
Pit Crew
Joined: Jun 2021
Posts: 138
Likes: 32
From: FL
couple months. The car drives fine, even into high speeds, it just doesnt rev above 3000. Most of the time I didn’t even have any engine lights at all. (Until recently)
I drive the car very light considering, I don’t push it hard. Really lost for the solution lol. Hoping one of these repairs eventually does it
I drive the car very light considering, I don’t push it hard. Really lost for the solution lol. Hoping one of these repairs eventually does it
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Pole Position
Joined: Sep 2018
Posts: 265
Likes: 72
From: New South Wales
I don't think we have found the root cause yet. Which means if the cats are fried and if replaced, any new cats will have similar early expensive demise from whatever is causing the main problem
Again all this is speculation on possibility without data to back it up. It could also just be the maf. Or a blocked fuel supply,.Or faulty O2 sensor. Or a faulty throttle body sensor or motor.or.or.or... Recording some obd sensor data would help narrow down what is actually occurring.
At least once the new MAF is in (which may very well fix it) we can then rule out the maf. And the vacuum hoses have been replaced so we can eliminate unmetered air.
Thread Starter
Pit Crew
Joined: Jun 2021
Posts: 138
Likes: 32
From: FL
MAF just arrived today. I installed it, the engine starts up fine, sounds better than the hesitated startup I was having before the new MAF. The engine codes (P0171 and P0174) have both been cleared and so far have not come back.
In terms of revving, in neutral it seems to rev the same as when driving. It still does not go above 3000. I did get it to pass 3000 slightly (maybe 3400) when I stepped on the pedal hard, but it's still not revving like it should.
Here's my data from my OBD2: Hopefully this suffices, this is just a cheap scanner from amazon
I apologize for the photos being out of order. Imgur did me dirty. There are currently no engine codes on.
https://imgur.com/a/En3wvLT
edit: both codes returned. P0171 and p0174
In terms of revving, in neutral it seems to rev the same as when driving. It still does not go above 3000. I did get it to pass 3000 slightly (maybe 3400) when I stepped on the pedal hard, but it's still not revving like it should.
Here's my data from my OBD2: Hopefully this suffices, this is just a cheap scanner from amazon
I apologize for the photos being out of order. Imgur did me dirty. There are currently no engine codes on.
https://imgur.com/a/En3wvLT
edit: both codes returned. P0171 and p0174
Last edited by teaa; Dec 11, 2021 at 02:17 PM.
Pole Position
Joined: Sep 2018
Posts: 265
Likes: 72
From: New South Wales
What code reading set up are you using? I presume the moto 69033. Do you have any others? Are you able to data log with it? Or view the O2 sensor data as a graph?
Last edited by Aus430; Dec 11, 2021 at 04:46 PM.
Thread Starter
Pit Crew
Joined: Jun 2021
Posts: 138
Likes: 32
From: FL
if you mean log it to a memory card no this scanner doesnt offer that.
not able to view the o2 sensors as a graph, only the raw data itself
Can you recommend any budget scanners that allow me to do all that?
Pole Position
Joined: Sep 2018
Posts: 265
Likes: 72
From: New South Wales
What's the bluetooth one? Like an ELm327 style dongle? If so thats perfect
Install the ap 'car scanner' on your phone. It's free with ads or a couple of bucks for non ads version. It will allow you to configure 'dashboards' and will data log your trips if the app is running and connected.
The dash to configure is one that shows sensors:
Throttle position sensor
Maf
Engine temp
Speed
Rpm
All 4 O2 sensors
Ltft for both banks
Ignition timing
Record a 15-30 minute trip, one where the call for 3000rpm thing is happening so we can see what the computer is doing and how the sensors are responding
Disconnect for the car exit the app, go back into the app then you can see you data file recorded there.
Install the ap 'car scanner' on your phone. It's free with ads or a couple of bucks for non ads version. It will allow you to configure 'dashboards' and will data log your trips if the app is running and connected.
The dash to configure is one that shows sensors:
Throttle position sensor
Maf
Engine temp
Speed
Rpm
All 4 O2 sensors
Ltft for both banks
Ignition timing
Record a 15-30 minute trip, one where the call for 3000rpm thing is happening so we can see what the computer is doing and how the sensors are responding
Disconnect for the car exit the app, go back into the app then you can see you data file recorded there.