MAF check engine light and transmission help

[heeroyuy01195]

I hope this is in the right spot but here goes, a few days ago I had my car in the shop to have the clutch changed due to grinding going from 3rd to 2nd gear. When I received the car there was a knocking noise when I moved off, pulled the car apart and found that my Transmission mount was the problem. During the process of removing the battery and the tray to inspect and reinstalling it, I picked up a check engine light (nothing related to the intake was removed aside from cable ties). The OBD reader said it was an issue with the MAF (or at least that's what the mechanic told me it said). He couldn't clear the code and recommended I just pull the negative terminal for a bit to reset the car. I did that and I still have the CEL. When the car starts it will hesitate a bit, sputter, then finally start up. While driving there is virtually no power when trying to accelerate.

I pulled the car apart on my own to check if anything might have been forgotten during reassembly but everything checks out and i still have a CEL. I removed the MAF to take a look if it might have been damaged but it looks fine (I can't recall but is the side facing the filter supposed to be slightly black?). I can't think of anything else to check. I reinstalled the stock intake (which seems to delay the check engine light from coming on for a bit) but that didn't stop it. The car's been sitting for about an hour without the negative on now, going to check it tomorrow to see if it goes away. Any other ideas? Anything I should check that I might have missed?

On a side note, the car still grinds from 3rd to 2nd. Changed to a Competition Clutch (stage 1) and Royal Purple transmission fluid, any thoughts on this matter? Thanks in advanced!

[CTScott]

Knowing the actual code would help a lot, but seeing as it comes back so quickly, it may be a damaged wire, as opposed to a bad sensor. Follow the MAF wiring as far as you can and check for anyplace where is may have been pinched during the tranny pull.

[CrankyOldMan]

As far as the grinding goes, if it's only in 2-3 then it may be a worn synchro ring on that side of the hub. Only way to fix that is to pull the gearbox and open it up. Opening it is pretty easy if you have the right tools, as is changing the non-fixed gears. Putting it back together is a different story, and I haven't tried that yet.

[heeroyuy01195]

Thanks for the heads up Scott, I'll look for damaged/loose wires tomorrow when the suns out. As far as the code goes, I'll have to see if I can get my hands on my cousin's code reader.

[heeroyuy01195]

Cranky, I was thinking the same thing but I didn't want to accept it lol. I've never worked on transmissions before so that'll have to wait until I can get someone more experienced to do it with/for me. Thanks for the advice!

[nightstalker]

I had same problem with maf but turned out the sensor got fried due to sand storm after passing threw az. I had to replace it but you should try cleaning it first if the wire arent pinched.

[heeroyuy01195]

nightstalker, do you have any recommendations on what to clean the MAF with? Thanks!

[nightstalker]

Mass airflow cleaner from autozone. Costs bout $6 to $8 cant remember how much I payed

[goliath1812]

CRC Mass Air Flow cleaner

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Mass-Air-Flow-Sensor-Cleaner-CRC_7070079-P_N3232_T%7CGRP2030C_____

[heeroyuy01195]

Cleaned the MAF sensor and it didn't help. Also checked all the wires and they seem to be in good order. I managed to get the code that it's throwing, P0103. According to the reader it says it's an issue with my MAF sensor. Any thoughts?

[CTScott]

P0103 is Mass or Volume Air Flow Circuit High Input. Unfortunately, because of the bridge arrangement within the sensor, a Circuit High Input and a Circuit Low Input will give the same results, so you can't tell whether the sensor is open or shorted.

If you look at page 91 of the "Engine Control" section of the service manual, it shows how to check for continuity between the ECM connector and the MAF connector. Doing so will verify if the issue is a wire issue or sensor issue.

The service manual can be downloaded from Micro Image:

http://www.microimageonline.com/forums/showthread.php/4232-YARIS-FILES

[heeroyuy01195]

P0103 is Mass or Volume Air Flow Circuit High Input. Unfortunately, because of the bridge arrangement within the sensor, a Circuit High Input and a Circuit Low Input will give the same results, so you can't tell whether the sensor is open or shorted.

If you look at page 91 of the "Engine Control" section of the service manual, it shows how to check for continuity between the ECM connector and the MAF connector. Doing so will verify if the issue is a wire issue or sensor issue.

The service manual can be downloaded from Micro Image:

http://www.microimageonline.com/forums/showthread.php/4232-YARIS-FILES

With both the C20 and C26 connectors disconnected as per the manual, my multimeter read stayed fixed at 1 for every test point. (The multimeter stays at 1 while not connected to anything during resistance checks so I'm assuming that it did not read any resistance?)

With the C20 ECM connector CONNECTED and the C26 MAF connector DISCONNECTED I got these values:
Check for Short
15.22k ohm

Check for Open
75.3K ohm

The check for open seems crazy high compared to what was stated in the manual.

[CTScott]

With both the C20 and C26 connectors disconnected as per the manual, my multimeter read stayed fixed at 1 for every test point. (The multimeter stays at 1 while not connected to anything during resistance checks so I'm assuming that it did not read any resistance?)

With the C20 ECM connector CONNECTED and the C26 MAF connector DISCONNECTED I got these values:
Check for Short
15.22k ohm

Check for Open
75.3K ohm

The check for open seems crazy high compared to what was stated in the manual.


With the connectors disconnected, you should be measuring from the ECM connector to the MAF connector for each signal wire. Is that what you were doing when your meter showed the open circuit indication?

[heeroyuy01195]

Yes I did that but I'm going to try checking again in the morning when there's some day light out and an extra pair of hands. Should I have the battery disconnected or connected when checking?

[CTScott]

Yes I did that but I'm going to try checking again in the morning when there's some day light out and an extra pair of hands. Should I have the battery disconnected or connected when checking?

When pulling the ECM connector it is not a bad idea to pull the battery.

[heeroyuy01195]

My leads on my multimeter were too thick to make contact with the ECM connector and I must not have noticed it last night. Anyways, I just redid everything and here's what I got:

Check for open:
C26-3 to C20-118 = 0.2 to 0.6 ohms
C26-2 to C20-116 = 0.3 ohm

Check for short:
C26-3 to Ground = No Reading
C20-118 to Ground = No Reading

For the grounding point I used the one on the driver's side shock tower and the negative terminal that goes onto the battery. I'm guessing that my mechanic must have knocked a wire loose somewhere?

[CTScott]

My leads on my multimeter were too thick to make contact with the ECM connector and I must not have noticed it last night. Anyways, I just redid everything and here's what I got:

Check for open:
C26-3 to C20-118 = 0.2 to 0.6 ohms
C26-2 to C20-116 = 0.3 ohm

Check for short:
C26-3 to Ground = No Reading
C20-118 to Ground = No Reading

For the grounding point I used the one on the driver's side shock tower and the negative terminal that goes onto the battery. I'm guessing that my mechanic must have knocked a wire loose somewhere?

Your results verify that the wiring between the ECM and MAF are intact (and not shorted), so it does appear that your MAF is bad.

[heeroyuy01195]

Thanks Scott, but shouldn't I still be getting a resistance reading when testing between the ECM to ground and the MAF to ground? I just want to be sure before I get a new MAF sensor. Thanks for all of the help Scott, much appreciated!

[CTScott]

Thanks Scott, but shouldn't I still be getting a resistance reading when testing between the ECM to ground and the MAF to ground? I just want to be sure before I get a new MAF sensor. Thanks for all of the help Scott, much appreciated!

No. Those two signal wires should not show continuity to ground, otherwise they would be shorted.

[heeroyuy01195]

Okay thanks Scott, just wanted to double check. I saw in the manual on pg 91 that I was supposed to be reading 10k ohms or more between CT26-3 and ground or C20-118 and ground for the "check for short" so I thought there was supposed to be a connection there. Thanks for all the help!

[CTScott]

Okay thanks Scott, just wanted to double check. I saw in the manual on pg 91 that I was supposed to be reading 10k ohms or more between CT26-3 and ground or C20-118 and ground for the "check for short" so I thought there was supposed to be a connection there. Thanks for all the help!

By 10K or more, they are saying that there should not be a low resistance connection to ground, which would be a short.

[heeroyuy01195]

Yeah it just clicked in my head a little while ago what they were getting at lol. I'm not sure what I was thinking earlier; stupid me moment I guess.

[heeroyuy01195]

Swapped the MAF out yesterday morning, car runs like a champ again. Thanks so much for the help Scott!