Three common problems and fixes for the 2001 Corolla
This post is intended for those who have only basic tools and knowledge. Obviously, you need a scan tool to get the trouble codes, if you don't have one, get one, it will quickly pay for itself.
Here's what Carfax says about the '01 Corolla:
Quote:
|
Occasional problems on this vehicle are failures of the Mass Air Flow (MAF) Sensor, Canister Closed Vacuum Switching Valve and Pressure Sensor Vacuum Switching Valve. Problems with the MAF Sensor, Canister Closed Vacuum Switching Valve and the Pressure Sensor Vacuum Switching Valve can cause the Check Engine Light to illuminate. On some vehicles, the MAF Sensor can be cleaned, and does not need replacement. The cost to replace the Canister Closed Vacuum Switching Valve is estimated at $44.18 for parts and $45.50 for labor. The cost to replace the Pressure Sensor Vacuum Switching Valve is estimated at $75.68 for parts and $65 for labor. The cost to replace the MAF Sensor is estimated at $151.10 for parts and $58.50 for labor. All prices are estimates based on $65 per flat rate hour and do not include diagnostic time or any applicable sales tax.
|
Somehow I think the above repairs would be more expensive in the real world. If anyone had these done by a dealer, I'd be curious to know what it cost, just to see how much money I saved.
I have had both the VSV problem and the MAF problem (occurred at separate times). Below is how to fix them. These are very common problems for this vintage of Corolla and other Toyotas that use the same technology.
Vacuum Switching Valve (VSV) - Codes P0440, P0441, P0446
There are two VSVs. One is up at the air cleaner (according to my dealer this one almost never fails) the other one (the one that does fail - wouldn't you know it) is down underneath the car beside the gas tank, and adjacent to the charcoal canister. Presumably it fails because it is more exposed to splash from the road. One clue that it is a problematic VSV is that the above 3 codes appear at the same time. This problem does not affect vehicle driveability, although it might be a problem when you go for your emissions test. Replacing this valve is not hard but it is uncomfortable because you're lying on your back looking up at the VSV (unless of course you have a hoist - which I don't) and dirt is falling on your face. You just have to pull off a short (few inches) length of tubing which obstructs access to the VSV. This tube is not clamped, you just pull it off, it is a larger diameter with a small tube branching off. Once you have pulled that off, you have a better view of the VSV. It is held by one Phillips screw, which is hard to get at. You would need a right-angle screwdriver; I don't, so I just managed to get it off by grabbing it with a pair of pliers, and turning it bit by bit. Narrow vice-grips would be good too. Feel free to do much cursing while attempting to remove screw. When the screw is removed, undo the electrical connector, and pull off the two tubes from the valve. Out with the bad, and in with the good. In my opinion the VSV is held quite firmly by the attached hoses and electrical connector. I didn't try to get that screw back in, it is just not worth the effort. You could use a cable tie to secure the VSV quite well. Reset your CEL and congratulate yourself.
Mass Air Flow (MAF) - Code P0171 (system running too lean)
This also does not affect driveability (unless you're an aggressive type) and you might find your fuel economy actually improves (I did). I presume Toyota designers had their reasons for not having this as a normal operating condition. Anyway this problem is very easy to fix. The MAF determines how much air for combustion is being sucked in by your engine at any given moment, which is important for setting the appropriate fuel-air ratio. What happens is that over time, the sensing elements in the MAF get coated with black goo from all the air that is going through them. It is located under the hood and is installed on the intake air filter housing. Undo the electrical connector, and it is removed from the air filter housing by uncrewing two Phillips screws. Very simple, takes 5 minutes. There are two sensing elements, one is in plain view, the other is concealed in an air channel and much smaller. You can see the smaller one by looking down the channel. It looks like a small bead suspended by two wires. Just spray a solvent on them to clean them off. You will see the black goo visibly get washed away. I used disc brake cleaner, which is just isopropyl alcohol with a propellant. Do not use WD-40 or similar lubricating products because they leave an oily residue. Put it back in, reconnect the electrical, reset the CEL, and you're done!
Here is a photo of the MAF. It's for a Tacoma/4Runner but as I said, the technology is the same (the sensor is identical).
So far I haven't had the third common problem mentioned above (Pressure Sensor Vacuum Switching Valve), I imagine it's a similar process to the VSV replacement, since it is located right beside the VSV.
Linear Mode
