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Discussion Starter · #1 ·
I’ve had my 2012 since about August 2020. The first time that outside temps got down to around 15 F, my engine threw these codes. P0172 and P0175, System too rich bank 1 and 2. The car ran perfectly, and the CEL went out on its own the next day. Since then it’s been coming on and off over and over. Much less when it’s above 10F or so, and a lot more now that we’re in the -20’s or more. My mechanic says he doesn’t think it’s the O2 sensors because it’s usually both banks complaining.

He wants to start with changing the purge valve.

Does anyone have any experience with this or have a better idea of a place to start troubleshooting?
 

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I’ve had my 2012 since about August 2020. The first time that outside temps got down to around 15 F, my engine threw these codes. P0172 and P0175, System too rich bank 1 and 2. The car ran perfectly, and the CEL went out on its own the next day. Since then it’s been coming on and off over and over. Much less when it’s above 10F or so, and a lot more now that we’re in the -20’s or more. My mechanic says he doesn’t think it’s the O2 sensors because it’s usually both banks complaining.

He wants to start with changing the purge valve.

Does anyone have any experience with this or have a better idea of a place to start troubleshooting?
Make sure the air filter is clean.
Clean the Mass Airflow Sensor (MAF), remove the MAF sensor, then using CRC Electronic Cleaner or MAF Cleaner, spray a few short bursts directly into the electrodes. Let condensation dry thoroughly. Reinstall.
Make sure the air intake hose is cracked free and clamps are tight.
 

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Check the coolant temp sensor readings before a cold start and then fully warmed up.
 

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I’ve had my 2012 since about August 2020. The first time that outside temps got down to around 15 F, my engine threw these codes. P0172 and P0175, System too rich bank 1 and 2. The car ran perfectly, and the CEL went out on its own the next day. Since then it’s been coming on and off over and over. Much less when it’s above 10F or so, and a lot more now that we’re in the -20’s or more. My mechanic says he doesn’t think it’s the O2 sensors because it’s usually both banks complaining.

He wants to start with changing the purge valve.

Does anyone have any experience with this or have a better idea of a place to start troubleshooting?
If it's the purge valve and it's stuck partially or fully open you'd probably have a hard time starting the engine after a tank fill up and notice a rough running engine for a few minutes after. You can temporarily clamp off either hose to/from it and see if the codes reappear. If anything, very cold weather would reduce fuel evaporation so there would be less fumes to purge in the canister.

Temperature does affect the Mass Air Flow sensor. There's a small heater in it that sends a signal to the computer to adjust the amount of fuel depending on how much the air passing by it cools the heater's wire. The more throttle, the more air passes the wire cooling it more which triggers more fuel. Very cold air will also cool the wire. The system is temperature compensated but it's not foolproof and if the wire is dirty it can send false readings. MAF spray can cleaners are easy to find and use.

Speaking of temperature, when the engine starts up, more fuel is provided to keep the mixture rich due to lower volitility, condensation, denser O2 levels, etc. If your thermostat is stuck open, the engine will take much longer to reach operating temperature which keeps the mixture rich. Open the radiator cap when the engine is cold before it's started for the day and make sure there is no coolant flowing right after startup. If you see movement before the engine warms up, replace the thermostat.

Make sure your mechanic checks the MAP (Manifold Absolute Presssure) sensor. If it's sending too high a reading the computer will compensate for the higher pressure with more fuel. Unlike the MAF, the MAP does also take into account the incoming air's actual temperature and engine rpm, so it is temperature sensitive and like any electronic gizmo can fail.

The MAF, MAP and throttle position sensor all give the ECU information on how much fuel the engine needs to have the ideal 14:1 mixture. 2 out of 3 isn't good enough and will throw the CEL warning. The freeze frame data should steer you or your mechanic to unusual readings and where they're coming from. But the MAF and MAP are likely culprits when the air temp is very cold, IMO.

Also check the air filter and make sure the infrastructure and flexible tubing have no leaks. Also check vacuum hoses for leaks.
 

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Discussion Starter · #5 ·
Thank you all so much for your replies, I'll look at these items and let you all know how it goes.
 

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Could be a dead bug, butterfly wing blocking the MAF. I'd clean that first and see if it fixes it. Every one should own a can....
144941
 

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Discussion Starter · #8 ·
Could be a dead bug, butterfly wing blocking the MAF. I'd clean that first and see if it fixes it. Every one should own a can....
Dumb question.... I have googled the MAS and know where it is now and what it looks like. For cleaning it, just set it on a paper towel and hose it down with the spray? Or only spray into the electrical connectors where the plug goes? Or just the sensor area where it inserts into the hose?
 

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Dumb question.... I have googled the MAS and know where it is now and what it looks like. For cleaning it, just set it on a paper towel and hose it down with the spray? Or only spray into the electrical connectors where the plug goes? Or just the sensor area where it inserts into the hose?
No soaking.
You can spray the conectior and the electrodes that are visible. Just trying to knock the dust off the electrodes. I use the little red straw that comes with the can.
Condensation will form if sprayed a lot. Let dry thoroughly.
 

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Could be a dead bug, butterfly wing blocking the MAF. I'd clean that first and see if it fixes it. Every one should own a can....
View attachment 144941
Hopefully he will find the rest of the bug in the air filter.

This is, hands down, the absolute best electronic cleaner I have ever used. It's especially good at cleaning contacts really well when low voltage signals need to get through plus it leaves behind a protective coating. Don't know yet what the effect of the coating is on the MAF wire but I'll know soon. Best for connectors or any slide contact. Little pricey but well worth it. Amazon carries it.
144942
 

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Hopefully he will find the rest of the bug in the air filter.

This is, hands down, the absolute best electronic cleaner I have ever used. It's especially good at cleaning contacts really well when low voltage signals need to get through plus it leaves behind a protective coating. Don't know yet what the effect of the coating is on the MAF wire but I'll know soon. Best for connectors or any slide contact. Little pricey but well worth it. Amazon carries it.
View attachment 144942
CRC Electronic Cleaner drys with no residue. You would not want any film or protective coating on this sensor. The CRC MAF Cleaner is more expensive but I've never had issues using the CRC Electronic Cleaner on my MAFs.
 

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CRC Electronic Cleaner drys with no residue. You would not want any film or protective coating on this sensor. The CRC MAF Cleaner is more expensive but I've never had issues using the CRC Electronic Cleaner on my MAFs.
So far so good. I think the MAF reads current through the heater wire (or voltage drop) which is a function of temperature which the thin (molecule thin) protective coating doesn't affect. Oxidation is a far better insulator. (both electrical and temp) I'll confess if I have issues with it.

CRC makes a lot of different cleaners ... I wonder what the diff is between the electrical cleaner and MAF cleaner? I read the MDS list different ingredients.

Here's a twin pack that includes MAF and Throttle body cleaner that doesn't cost much. They also sell two hand cleaners ... one for the left and one for the right. Don't even think about asking what happens if you mix them up. It's not pretty.


144946
 

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Discussion Starter · #13 ·
Make sure the air filter is clean.
Clean the Mass Airflow Sensor (MAF), remove the MAF sensor, then using CRC Electronic Cleaner or MAF Cleaner, spray a few short bursts directly into the electrodes. Let condensation dry thoroughly. Reinstall.
Make sure the air intake hose is cracked free and clamps are tight.
So I made a discovery while doing your list above. When I bought the car in Aug I replaced the air filter. The filter box has 4 screws, 2 close to the side of the car and 2 close to the engine. Well not only did I somehow not fasten the 2 down by the engine, at all, but the filter box cover was actually resting on/pinching a cable that runs right by, I think it's some winterization power cords in some split loom. So bottom part of the cover not fastened closed, AND propped open a bit.

I felt real dumb when I discovered that!

The filter was a bit dirty so I replaced it, got the box cover back on securely, and tightened ALL 4 screws down this time. I'm heading out in a bit to see what happens with the CEL.
 

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Don't feel bad. We all learn from our mistakes. By posting your findings, it helps others too. Thanks!👍👍👍
 

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Hopefully he will find the rest of the bug in the air filter.

This is, hands down, the absolute best electronic cleaner I have ever used. It's especially good at cleaning contacts really well when low voltage signals need to get through plus it leaves behind a protective coating. Don't know yet what the effect of the coating is on the MAF wire but I'll know soon. Best for connectors or any slide contact. Little pricey but well worth it. Amazon carries it.
View attachment 144942
I've used Caig products for 40 years in electronics and automotive contact applications. Deoxit is spectacular...for its intended purpose. As a cleaner for MAF or MAP, NO. The coating it leaves on the MAF sense wires is a no-no, as it will thermally insulate the cold wire and get cooked on the hot wire. Best to use contact cleaner or purpose formulated MAF sensor cleaner. Some have used brake cleaner (any variety) with success and without sensor damage. Best NOT to use carb or throttle body cleaner, as these are really caustic and can pit the coating on the sense wire type sensors, changing the calibration somewhat. If the sense wires were really dirty to begin with, any cleaner is likely to improve sensor performance , but may not restore factory calibration and sensitivity.
 

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I've used Caig products for 40 years in electronics and automotive contact applications. Deoxit is spectacular...for its intended purpose. As a cleaner for MAF or MAP, NO. The coating it leaves on the MAF sense wires is a no-no, as it will thermally insulate the cold wire and get cooked on the hot wire. Best to use contact cleaner or purpose formulated MAF sensor cleaner. Some have used brake cleaner (any variety) with success and without sensor damage. Best NOT to use carb or throttle body cleaner, as these are really caustic and can pit the coating on the sense wire type sensors, changing the calibration somewhat. If the sense wires were really dirty to begin with, any cleaner is likely to improve sensor performance , but may not restore factory calibration and sensitivity.
Thanks, the CRC MAF cleaner just arrived from Walmart so I'll spritz some of it on the greasy hot wire and see what happens. I ordered some parts to do 105k maintenance and that is among the group of parts on the way such as the PCV valve, EGR valve and gasket, MAF, MAP, and the VTEC solenoid. Everything is working so I'm going to take it slow replacing things so I know which new part caused the problem. haha.. Based on some strange problems posted here lately, replacing stuff around the engine bay is like that game Operation, if you touch the wrong thing, bend the wrong harness, move the wrong connector ... bzzzzzz ... it's Chistmas tree time!
 

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So ...like a good listener, I heeded my Piloteer brotheren and got some CRC MAF cleaner and blew off the MAF. Gave it a good dowsing to remove any traces of the caig cleaner previously used. I'll let it dry off for a while and put it back in and see how many lights and DTCs I can trigger.

 

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Nice sensory video :) So the outside of the MAF doesn't really need much cleaning, other than an external temp sensor. Use the pipette and forward, then back flush through the rectangular holes, thus flushing cleaner across the sense wires.
 

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So ...like a good listener, I heeded my Piloteer brotheren and got some CRC MAF cleaner and blew off the MAF. Gave it a good dowsing to remove any traces of the caig cleaner previously used. I'll let it dry off for a while and put it back in and see how many lights and DTCs I can trigger.

Nice sensory video :) So the outside of the MAF doesn't really need much cleaning, other than an external temp sensor. Use the pipette and forward, then back flush through the rectangular holes, thus flushing cleaner across the sense wires.
Yes, the idea is to knock the dust off those electrodes you can see in those openings. I'd use the little red straw to direct a couple of shots straight in there.
 

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Yes, the idea is to knock the dust off those electrodes you can see in those openings. I'd use the little red straw to direct a couple of shots straight in there.
When I realized how thin (fragile) some of the wires are (needed a jeweler's loop to see them) I decided not to use the little red straw for rear of either touching them or putting too much concentrated pressure/spray on them.
Notice how thin the wire and leads are (red arrows) compared to a standard 1/4 watt component lead (green arrow).

I'm pretty sure I got them clean keeping 6" back with a full fan spray and dowsing the heck out of them. They didn't look dusty or dirty to begin with.

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