CEL Code P0172: Help Needed
#21
Originally Posted by drjohnson36
Originally Posted by SCIONOSIS
Originally Posted by drjohnson36
If the water temp sensor was fried, the temp gauge on the dash would stay at the bottom. I'm sure he would've noticed that if it was the problem.
Also... the A/F ratio runs rich at startup because the O2 sensors are too cold to operate, so the engine runs on an open loop (rich). Once they heat up, the sensors are able to function, and the engine starts closed loop operation (relies on sensor readings to adjust A/F ratio). As far as I'm aware, water temperature should have almost nothing to do with A/F ratio.
As for the OP's problem... definitely check for leaks around your intake. Either listen for a hissing, or spray soapy water and look for bubbles. If there are no leaks, check the MAF first, then check the O2. A funky A/F ratio could be caused by either, and either one will throw the same code you've described. BUT, if the sensors were defective, you'd also see other codes. I'm convinced it's a leak somewhere.
Also... the A/F ratio runs rich at startup because the O2 sensors are too cold to operate, so the engine runs on an open loop (rich). Once they heat up, the sensors are able to function, and the engine starts closed loop operation (relies on sensor readings to adjust A/F ratio). As far as I'm aware, water temperature should have almost nothing to do with A/F ratio.
As for the OP's problem... definitely check for leaks around your intake. Either listen for a hissing, or spray soapy water and look for bubbles. If there are no leaks, check the MAF first, then check the O2. A funky A/F ratio could be caused by either, and either one will throw the same code you've described. BUT, if the sensors were defective, you'd also see other codes. I'm convinced it's a leak somewhere.
I doubt it would be a vacuum leak cuz if it were, he'd have dtc P0171 (fuel system too lean). Ofcoarse, intake vacuum leaks introduces more air into the mixture creating a lean condition.
I've not seen a single car on any kind of fuel injection that relies on the water temp sensor to determine closed/open loop. The reason your exhaust smells like fuel when you start your car up early in the morning is cuz the O2 sensor is cold, and won't work until it hits at least 400 degrees. The water temp sensor shouldn't have a thing to do with the system. Old carbureted engines used a choke to cause the engine to run rich because cold fuel doesn't vaporize as easily as warm fuel (for inherently obvious reasons). The rich mixture allowed the engine to burn until it heated up, after which a thermostat would release the choke, causing a more lean A/F ratio. Fuel injected engines don't have this problem with vaporization because the fuel is atomized by the injector nozzle.
Also someone said something about the K&N. I had a buddy who fried his MAF cuz a little oil got on the sensor. Definitely check that.
As for the second part, I do agree that fuel vaporizes at the injector. But, for the ECU to be able to go into closed loop, it has to know engine temps thru the CTS first. So yeah, CTS signal is vital information for the engine to operate efficiently in its environment.
#22
Originally Posted by drjohnson36
As for the OP's problem... definitely check for leaks around your intake. Either listen for a hissing, or spray soapy water and look for bubbles.
There is a primitive way to check for leaks in your intake. This is to take a propane torch and blow propane (not a flame) around the intake. If the rpm's jump or dip, you found your leak. I don't recommend doing this though.
#23
Alright so I pulled out the MAF and the bulb inside it is partially amber and the rest is black?
Did the oil cake itself onto it, or is the MAF fried? Either would that be the problem?
________
Did the oil cake itself onto it, or is the MAF fried? Either would that be the problem?
________
Last edited by MR_LUV; 04-09-2019 at 01:43 PM. Reason: Awarded 10 Year Badge
#24
^ That bulb color is normal. However, the bulb part of the MAF sensor is not the only thing you would clean. If you look down the hollow chamber next to the bulb with a flashlight, you'll see another element of the sensor. I believe that part of the sensor is what determines air temperature, density, and humidity. Like one other guy said, clean that other element you did not see with sparing amounts of brake cleaner. It's not recommended to do so, but it doesn't hurt to see if it will correct the problem if it's just a dirty MAF sensor. Brake cleaner evaporates quickly, but when you spray inside the chamber with a straw attached to the spray nozzle, be careful that you don't poke the element with the straw. Also, spray inside the chamber with the opening facing the ground. That way the grime washes out the sensor. If this does not correct your problem with a different filter, I recommend you take it to a certified mechanic in your local area. They'll do a complete test and inspection of other components related to that DTC P0172.
Don't forget to follow up here once your problem is fixed.
Don't forget to follow up here once your problem is fixed.
#27
P0172
Hey, so what was the actual problem you had, and how did you solve it. I'm having a similar problem with Code P0172, car doesn't die but does seem to hesitate and stutter a bit at around 3000rpm.
Also feels like lost a bit of power. Car was running fine until I took off the intake to clean the throttle, after that it started to act weird and the code came on.
Any help would be greatly appreciated.
_____
Also feels like lost a bit of power. Car was running fine until I took off the intake to clean the throttle, after that it started to act weird and the code came on.
Any help would be greatly appreciated.
_____
Last edited by MR_LUV; 04-09-2019 at 02:29 PM.
#28
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Hey, so what was the actual problem you had, and how did you solve it. I'm having a similar problem with Code P0172, car doesn't die but does seem to hesitate and stutter a bit at around 3000rpm.
Also feels like lost a bit of power. Car was running fine until I took off the intake to clean the throttle, after that it started to act weird and the code came on. Any help would be greatly appreciated.
Also feels like lost a bit of power. Car was running fine until I took off the intake to clean the throttle, after that it started to act weird and the code came on. Any help would be greatly appreciated.
I would read > Page 1, Post 7 by toyoguy27 Dated 10-08-2008, 07:00 PM ▲▲ LOOK UP! ▲▲ to page 1
I am not a Tech, but according to his Profile (Click on his User Name) he says he is a Toyota Master Technician, so I would lend credence to what he said:
He says that "Code P0172 is a MAF problem. And you should Reset your ECU by disconnection the POS and NEG of the battery and touch then together about 30 sec and then reconnect."
It's possible when you took off the Intake, you might have accidentally contaminated the MAF Sensor. Try Cleaning your MAF Sensor and Resetting your ECU to relearn.
How to Detect and Clean a Faulty Mass Airflow Sensor
No Guarantee, but worth a try.
MR LUV
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Last edited by MR_LUV; 04-12-2019 at 03:20 AM.
#29
P0172
Thanks for the reply, i actually did take out the MAF sensor and cleaned it with mfa cleaner, put it back on and drove to work the next morning, light still came on. Disconnected the battery during lunch for a minute or two but didn't touch the pos and neg terminals together. Should i try it again and is that safe to do?
#30
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Thanks for the reply, I actually did take out the MAF sensor and cleaned it with MAF cleaner, put it back on and drove to work the next morning, light still came on. Disconnected the battery during lunch for a minute or two but didn't touch the Pos and Neg terminals together.
Should I try it again and is that safe to do?
Should I try it again and is that safe to do?
Go4shoped in Post # 18 says "Do not touch the terminals together". "Just take the negative terminal off, and try to start the car."
toyoguy27 in his Profile says he is a Toyota Master Technician. So there is No Consensus on whether that is Safe or Not.
Perhaps, it's Safer to wait until someone else chimes in on the Subject and see if anyone else has experience the same problem?
And use the Infinite Scroll to Review the Related Threads Below. And also try using:
Sticky How To Advanced Search SL (Scion Life)
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Last edited by MR_LUV; 04-10-2019 at 02:04 AM.
#32
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That's all I can find on the Code P0172.
I would Concentrate on the Possible Causes, One by One, as a Process of Elimination.
Hope it Helps,
MR LUV
Last edited by MR_LUV; 04-09-2019 at 07:26 PM.
#35
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See> Post # 22 by Go4shoped Dated 10-10-2008, 09:59 AM
▲▲ LOOK UP! ▲▲
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Last edited by MR_LUV; 04-12-2019 at 03:19 AM.
#37
P0172
I didn't use brake cleaner, i specifically stated that i used maf sensor cleaner. Anyways i maneged to fix the problem by just unscrewing the air intake and putting it back to getting making sure everything was tight, also had to cut the end of one of the hoses that leads to the intake from the throttle because it was kind of cracked from one end. The. I disconnected the battery for a couple of hours to reset the ECU and the car is running normal again with no code.
#38
ok, my bad...some one in this post said they did...thought it was you...sorry...glad you worked it out...had the same thing with the cracked, rotted vac hose myself...probably the same one...little short one with a 90 degree bend that is hard to see behind the switch mounted to the intake tube behind the maf sensor??? i fixed it once, then replaced all of them suckas
#40
Took me two gas caps, a cap gasket and a few pulled hairs before I found it...my crack was on the back side where you needed a mirror to see it...I looked at that little biaaatch, and all the other what 2hoses in the entire system, several times before the mirror showed me the defect
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