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Learning, Sharing, and Teaching => Do it Yourself Discussion! => Topic started by: catccc on January 26, 2016, 02:54:36 PM

Title: Mass Air Flow Sensor Replaced - Check engine light still on! - updated!
Post by: catccc on January 26, 2016, 02:54:36 PM
The check engine light came on last week in my 2005 Toyota Matrix. I took it to a shop, and they diagnosed that the MAF Sensor was broken. They wanted $307 for the repair. I declined and asked just to pay for the diagnosis. The told me it was $65, but when I picked up my car, they told me I owed them nothing. So I took my car, got the part for $80 online and replaced it. Two screws and a cable, 5 minutes. (There was a huge range in cost of the part online, from mid $20s to $140s, I went somewhere in the middle, a well reviewed part on Amazon.)

I was told it takes a while for the car's computer to "learn" the new part, or calculate the gas/air mixture, so I shouldn't expect the check engine light to go off right away. Well, it's been a couple days and maybe 50 miles now, and the light is still on. Any ideas on how much time I should give it? It feels like it is running better (no more rough idle, better acceleration) but I'm just worried that it should have turned off already.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: forward on January 26, 2016, 04:20:32 PM

After you replaced the MAF did you clear the codes? You may want to try clearing the codes and then seeing if the CEL comes back. One time I read that it can take multiple (perhaps as many as 8) complete warm ups for a reset to occur on some emissions components - though I could be completely off on this.

I would try clearing the codes, see if it comes back. If it does, have the new code read and see if its the same error or a different one. Its possible they misdiagnosed it in the first place. If you get the codes you should be able to go to a vibe/corolla forum and see if someone can tell you what to do with that code. An auto parts store should be able to read the codes for you.

Good job on changing it out yourself.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: Spork on January 26, 2016, 04:24:57 PM

I'm also going to toss this out here...

First, as said, clear the codes.

If it comes back, then I'm going to suggest you check/replace the intake manifold gasket. This is a VERY common problem on these cars (and will fail again in 5 years or so). But it will only cost you about $3 to replace it.

These are a rubber manifold gasket and they just get compressed over time. It will create a leak and unmetered air enters the system. When this happens, it looks like a MAF failure, but it's just a leak.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: elcheapo on January 26, 2016, 04:30:16 PM
The check engine light came on last week in my 2005 Toyota Matrix. I took it to a shop, and they diagnosed that the MAF Sensor was broken. They wanted $307 for the repair. I declined and asked just to pay for the diagnosis. The told me it was $65, but when I picked up my car, they told me I owed them nothing. So I took my car, got the part for $80 online and replaced it. Two screws and a cable, 5 minutes. (There was a huge range in cost of the part online, from mid $20s to $140s, I went somewhere in the middle, a well reviewed part on Amazon.)

I was told it takes a while for the car's computer to "learn" the new part, or calculate the gas/air mixture, so I shouldn't expect the check engine light to go off right away. Well, it's been a couple days and maybe 50 miles now, and the light is still on. Any ideas on how much time I should give it? It feels like it is running better (no more rough idle, better acceleration) but I'm just worried that it should have turned off already.

I will tell you a good trick, when ever you get a check engine light, always and I mean always reset the codes 1st and drive around and see if it comes back on. There is a ton of times that its a false light or code in the computer. Sometimes sensors will jog crazy if you go through a big mud puddle or if you get a car detailed and they power wash your engine and get water in the spark plug tubes or if its freezing cold out a ton and I mean a ton of VW's get check engine lights. I have saved thousands upon thousands with just resetting the light and re drive testing it. About 75% of the time the light is a fluke ! Good Luck !
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: elcheapo on January 26, 2016, 04:31:43 PM

After you replaced the MAF did you clear the codes? You may want to try clearing the codes and then seeing if the CEL comes back. One time I read that it can take multiple (perhaps as many as 8) complete warm ups for a reset to occur on some emissions components - though I could be completely off on this.

I would try clearing the codes, see if it comes back. If it does, have the new code read and see if its the same error or a different one. Its possible they misdiagnosed it in the first place. If you get the codes you should be able to go to a vibe/corolla forum and see if someone can tell you what to do with that code. An auto parts store should be able to read the codes for you.

Good job on changing it out yourself.

Very good advice. I just basically told them the same thing.
Reset codes and re drive test and see if was just a fluke.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: kendallf on January 26, 2016, 07:04:32 PM
You can go to nearly any auto parts store and use an OBD-2 scanner to read and clear the codes on your car. Do that, write down what codes are there and then you can Google them to see common failure modes. Then as others have said, wait to see if a code comes back.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: lthenderson on January 27, 2016, 07:48:35 AM
Once you cleared the codes and if they come back, make sure you have an OEM MAF sensor. I've had lots of problems with non OEM stuff over the years when it comes to the emissions system. Different manufacturers have different warm up times for their components and if they take too long according to the computer, a fault code will be thrown. I've seen it with MAF and oxygen sensors. The latest example was replacing the spark plugs in my wife's vehicle as part of a general tune-up. The new plugs were compatible according to the manufacturer of the spark plug but I kept getting random cylinder misfire errors every few hundred miles or so. Eventually I bought OEM plugs and the problem went away.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: catccc on January 27, 2016, 09:13:59 AM
Thanks all for the advice (and the pat on the back!)

I will give it a full week of driving and see if it goes away on its own, if I can stand to wait. (Or maybe if I drive by an auto parts store, I'll see if they can check the code and clear it.)

If that doesn't work, I'll keep the manifold gasket in mind. I think I'm also waaay overdue for an air filter change, so I should probably pick up one of those, anyway.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: Janningc on January 27, 2016, 05:33:41 PM
A way to reset the entire system is to unhook the battery (negative first, then positive) and leave it unhooked for about 10 min. Longer will not hurt anything. This will reset most codes because you give the system the full amount of time to get rid of any load of power it has. I believe you said toyota so you shouldnt have to worry about re-coding any parts after you do this. FYI to Honda owners, if you try this you are going to need to have your radio code (found in the glovebox on the lefthand side outer, or in the maintenance manual but not always). I work in a collision shop and have found airbag codes and abs codes that a normal scanner cannot clear but this usually does the trick.
Good luck to you and with the cold driving conditions remember that even a 10 minute drive may not get your car up to operating temp, I have had to run cars for 30-60 minutes before the thermostat will open up.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: JordanOfGilead on January 29, 2016, 01:56:18 PM
Worst case, there are model specific forums for pretty much all cars. If nothing suggested here works, they might be able to give you a more in-depth solution to the problem.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: bradne on January 30, 2016, 09:17:30 PM
I will say that one of the best purchases I ever made was an OBD scanner from ebay that works with my smartphone through bluetooth. It pairs with an app (I use TORQUE), which is one of the very few apps I ever purchased. Since I live about 10 miles from the nearest auto parts store, I have been able to diagnose several vehicles (mine and neighbors) without having to go to town. Since diagnosing a problem is usually the hardest part of any auto repair it is money well spent. I probably have not paid a mechanic to work in my vehicles in about 10 years (If I had the scanner then I would not have done that one). The OBD scanner will read (and clear) codes. You can simply google the code and figure out what is wrong. I have probably used it about 10 times in the last couple of years. Diagnose, order the parts online and you can make repairs for a very small fraction of what a garage will charge you.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: daverobev on January 31, 2016, 03:42:44 PM
I will say that one of the best purchases I ever made was an OBD scanner from ebay that works with my smartphone through bluetooth. It pairs with an app (I use TORQUE), which is one of the very few apps I ever purchased. Since I live about 10 miles from the nearest auto parts store, I have been able to diagnose several vehicles (mine and neighbors) without having to go to town. Since diagnosing a problem is usually the hardest part of any auto repair it is money well spent. I probably have not paid a mechanic to work in my vehicles in about 10 years (If I had the scanner then I would not have done that one). The OBD scanner will read (and clear) codes. You can simply google the code and figure out what is wrong. I have probably used it about 10 times in the last couple of years. Diagnose, order the parts online and you can make repairs for a very small fraction of what a garage will charge you.

Agreed - any ELM 327 bluetooth one, any Android phone. Torque is excellent.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: moosieshorts on February 02, 2016, 12:32:48 PM
A way to reset the entire system is to unhook the battery (negative first, then positive) and leave it unhooked for about 10 min. Longer will not hurt anything. This will reset most codes because you give the system the full amount of time to get rid of any load of power it has. I believe you said toyota so you shouldnt have to worry about re-coding any parts after you do this. FYI to Honda owners, if you try this you are going to need to have your radio code (found in the glovebox on the lefthand side outer, or in the maintenance manual but not always). I work in a collision shop and have found airbag codes and abs codes that a normal scanner cannot clear but this usually does the trick.
Good luck to you and with the cold driving conditions remember that even a 10 minute drive may not get your car up to operating temp, I have had to run cars for 30-60 minutes before the thermostat will open up.

This is how I cleared my code after replacing an evap system part. The trick after clearing the code is that different vehicles have different "drive cycles" that reset the monitoring systems in order for them to measure things properly again, so it's possible that even after driving a while the issue remains without the light coming back on to tell you (although from the sound of it your vehicle is fixed). Some systems are really specific, like a cold start in a specific temperature range. I found this out when I got a "not ready" status on an emissions test. You'll eventually get through the drive cycle with normal driving but if it's cold where you are it might be almost spring before you're in the right temperature range. Someone please correct me if I'm wrong, I was trying to figure this stuff out after a long day.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: Making Cookies on February 08, 2016, 10:53:14 AM
I will say that one of the best purchases I ever made was an OBD scanner from ebay that works with my smartphone through bluetooth. It pairs with an app (I use TORQUE), which is one of the very few apps I ever purchased. Since I live about 10 miles from the nearest auto parts store, I have been able to diagnose several vehicles (mine and neighbors) without having to go to town. Since diagnosing a problem is usually the hardest part of any auto repair it is money well spent. I probably have not paid a mechanic to work in my vehicles in about 10 years (If I had the scanner then I would not have done that one). The OBD scanner will read (and clear) codes. You can simply google the code and figure out what is wrong. I have probably used it about 10 times in the last couple of years. Diagnose, order the parts online and you can make repairs for a very small fraction of what a garage will charge you.

I'll second that. Same dongle, same app, same good results.
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on!
Post by: catccc on February 19, 2016, 12:15:22 PM
Update!

So the light was on for weeks. I hadn't gotten around to getting the code read (I really don't want to own a thing I can borrow for free, despite recommendations from many here...)

Finally after work Wednesday I got the chance. I was going to go to Autozone, have the code read and the light turned off, and then pick up something at the grocery store. But I couldn't turn into the autozone b/c oncoming traffic was stopped and blocking my turn. So instead I went to the grocery store first. Then when i got back in the car to drive to autozone, the light was off.

It took waaay longer than I expected. It was about a month of driving, maybe 500 miles, but the light is finally off on it's own. I'm really grateful b/c if I had them read the code and turn it off first, I'd spend weeks worrying about it turning back on and wondering if I'd really resolved the problem.

Thanks all for your help!
Title: Re: Mass Air Flow Sensor Replaced - Check engine light still on! - updated!
Post by: Making Cookies on March 05, 2016, 01:36:56 PM
FWIW I think the car's computer has a long term memory of past faults to help with troubleshooting. The light goes off but the computer remembers what that fault was.

My Chevy ran out of gas the other day (non-functional gas gauge, usually lasts 399 miles, thsi time lasted 265 miles). While it stumbled down the street before it stalled it tripped the CEL with a misfire code. Refueled, and a few days of driving it reset the light automagically.