Hi Guys,

My 99 Z28 is due for a smog check, and the check engine light has been on for a while (yeah i know...) well anyway, the shop was nice enough to inform me that it will not pass with that light on, and they checked the code for me for free. it shows a MAF (Mass Airflow sensor) fault. of course I checked all the wiring and made sure everything to the MAF is connected securely... logic tells me i will need to replace the MAF and i should be able to successfully reset the check engine and get this smog going...

Has anyone else experienced this before, and maybe have some pointers on what might be serviceable on the MAF to at least get the thing through smog?

Thanks guys!

Joe

 

have you tried clearing the code to see if it comes back? once the code is tripped, it stays in the computer till it is erased.

clear it and if it comes back there is a problem. if not it was just a glitch

usually when the maf goes bad the car runs poorly

 

That is worth a shot! Can you tell me the steps to clear the code? if it is just a matter of removing the battery terminals, then that is not the issue, that has been done..

thanks!

 

Go to an Autozone or any parts stores, they usually offer free computer scans. Just have them clear the code with a scan tool, thats the right way.

 

You can clear the code(s) by resetting the PCM, but if you're going to have an inspection quick have someone just read/erase it. If it comes back on after a few cold starts post the code. If you already reset the PCM by removing the battery cables/fuses you'll need to put some miles on the car to make sure all the readiness tests are done, see www.obdii.com/drivecycle.html

 

Check the condition of the MAF. The wire inside can get gunked up esp if you are using a k&f filter using a little brack cleaner usually does the trickif it's ddirty.

 

I reset the code, but came right back. the wierd thing is, the car runs GREAT... the idle is perfectly smooth, and acceleration is excelent, never misses a beat. if my MAF is truly bad, wouldnt I be having all kinds of issues??

I dont want to order a new MAF if that isnt going to fix the problem... what do you guys suggest I do from here?

 

I had that happen to me. It ended up being that one of the prongs where the wire plugs into the MAF was bent. I bent it back up and made sure it went into the plug. Reset the code and all was well.

 

I'll try that tonight.

Last night i reset the ECM codes, and went for a drive in the hills for about an hour, i was stoked, the light didnt come back on!! I came home, parked the car, went inside to open the garage, as i'm pulling the car in... BLINK! the SES light comes back on... DOH!

I'll try your suggestion when I get home

How to reset ECM codes:
turn the key to on, but don't start the car
pull the IGN ECM and PWR ECM fuses (one is in each of the two fuse boxes under the hood)
wait about 30 seconds, replace the fuse, remove the key, and start the car. the SES light will be off, and the codes are cleared.

 

or pull the battery terminal for 10 mins or so.


what code exactly does it show? give us the number and maybe we can give a better answer.

 

my neighbor has a ODBII scanner, so i'm going to find out tonight... i'll post the code

 

got the error codes:

P0418 - "Secondary AIR injection system - relay malfunction"
P0412 - "Secondary AIR injection system valve malfunction"

I found that the 25A fuse for the air pump had blown (good news.. maybe...!) I didnt have a 25, but i had a 20A, popped that in, and it blew right away. i'm going to pick up a pack of fuses tomorrow, i'm going to try a 30A... if that blows, there is definately an issue, it is drawing too much current. if not, i'll put the correct 25A in, see how that goes. Does that sound about right?

If my air pump is in fact bad, what the HELL is that, and where can I find it?? This is not a component I'm familiar with!!

thanks again guys...

 

Thats weird I had that same problem replaced the fuse, and it hasn't blown that fuse since. anyways good luck.

 

see now that pisses me off...

my suggestion is to not go to THAT shop again

talk about a wild goose chase. now the way you describe the light coming on, and how it didin't that one time...makes sense. my car use to do the same thing (with the light) after i pulled the AIR pump off when i put headers in.

the air pump is the emissions provision that feeds air to the cats during warm up. it is located inside the fender well in front of the driver side tire, kiindda under the headlight. and the hoses from it run over each of th valve covers and down into flanges off the front of each exhaust manifold.

it is a commonly removed part when headers are installed, so you should be able to find one on the net if the pump is bad.

 

JFI - don't know if the 99's are different, but my AIR PUMP fuse is a 30 AMP - and sets P0412 on the second cold start with it removed.