CEL concern.

[detroit202]

CEL concern.

Ok people I searched its hard to search for MAS problems cuz you guys call it a bunch of different things MAS, MAF, mass airflow etc

heres my story

My CEL came on last month I did a scan and came up with

"fuel trim malfunction"

I disconnected the battery it was off for a few days then came back on I waited a couple more days and it turned off on its own.

2 weeks ago the CEL came on again I did not scan the car this time and went ahead and ordered a MAS from BMA auto parts in cali for like 290 last night.

After two weeks of staring at my CEL looking all ghetto low and behold my CEL light was OFF this morning after two straight weeks of being on.

So my MAS is coming in a couple days...

Should I wait for the CEL to come back on and rescan it? Or should I just install the new MAS

Ive had the car since 60,000 miles and now have 108,000 and never changed the MAS or know if its been done

Thanks for your replies ..

[Rocky]

Change MAS and reset the light by unplugging the battery so that you clear the codes and the car will be forced to relearn.


The MAS will sometimes trigger the light and sometimes it will not. It's finnicky but for sure you need to change the MAS.

[detroit202]

thanks i dident know about unpulgging the battery again after you change the mass..

should i install it first ... start the car then unplug the battery after

or just have the battery unplugged while i change it?

and do i need any special torx drivers or anything or is it just clips

thanks again

[Rocky]

Just install the MAS then unplug the battery. Becareful, you might have to reprogram your power windows and for sure keep the stereo code handy cause you'll need to re-enter that. There is an active thread about the windows.

All you need if i remember correctly is a screwdriver to loosen the clamp on one side..the other side is held on by these flip clips you can unclip with your hand. 2 min job....literally.

Good luck.

[detroit202]

thanks and for those who ever disconnect their battery sometimes the sunroof too needs to be reset it will open but not close you need to hold it in the up position (i think) for like 10 seconds. if thats not it there are only two more positions to try..

[SLAMMED_C]

if your replacing the MAS, you need to check lambda percentages.. closer to 0% is best.. or stayin near 0%.. say climbing up to 3 or 4% max (either going positive or negative)
if the lambda is very high.. like over 10%, maybe even as high as 15-20% you will need to check for a few things.. it can still possibly be the MAS at this point and 9 times out of 10 it is the MAS, check for vacuum leaks.. also leaking intake gaskets can cause lambda to rise.
check MAS kg/h flow.. depending on engine it will vary..
4: 8-16 kg/h (dont quote me on this one.. I cant remember off hand exactly)
6: 10-20 kg/h (normally sit at around 10-12 kg/h)
8: 10-20 kg/h (normally sit at around 10-12 kg/h)
(these flow rates are at idle)
sometimes they will sit at 8 kg/h (in 6or 8 applictaions), or drop to 8 kg/h after a light press on the throttle, if it dives down to 8kg/h for any length of time it can cause a fault and you will need to replace the MAS. for the 4 banger it may drop to 6 kg/h.
You WILL need to reset self adaptation after the replacement of the MAS, in order to recheck the values to see if the problem has been fixed.

normally for a MAS problem you will get a code of PO170, PO173.. so I dont think your problem is related to the MAS.. by the sounds of the code.. being fuel trim, I would think either fuel computer or O2 sensor.. something along those lines, but again wierder things have happened.. could be the mas still.
any rough idle?

[detroit202]

thanks,

my code was p0171 just doing a google seach i found on a toyota site that

the oxygen sensor and the Mass Air Flow Sensor (MAF) are common suspect items with this error.

so if its not my MAS ill replace the O2 sensor.. as well its only around $80 i think i found this too the order of things you should check when you get this code..my lazy ass hasent even opened the hood to see if maybe the hose is lose or something..oh well at least the MAS is towards the top of the list.. my CEL has been off for 2 days now on top of it..

Trouble Area
P0171
Air Induction System Leak
Injector Blockage
Mass Air Flow Meter
Engine Coolant Temperature Sensor
Fuel Pressure
Gas Leakage from the Exhaust System
Open or Short in the Oxygen Sensor or associated wiring
Oxygen Sensor Defective
Engine Control Unit