PDA

View Full Version : Engine Code 24, bad afm?



Melchior
02-17-2007, 05:53 AM
Checked my codes today, got a code 24. What scares me about this of course is that the Intake air temperature sensor is integrated into the AFM. (st185)

Besides praying for a loose wire, is there any other checks I can run on the AFM itself, or any suggestions on how to possibly correct it?

Also, this may sound like an obvious questions, but what are the performance related signs of this? e.g. bogging, misfires, etc...?

UPDATE: Diagnosed the AFM as per factory specs, seems to check out okay (45 ohms open, 251 closed between terminals E2 and VS) However, between E2 and THA i get NO READING, and THA is i'm assuming related to the temperature sensor.

If possible, can anyone reference a known good AFM and see what readings they get on E2 and THA?



[/I]


http://farm1.static.flickr.com/142/392696438_c2a4add98e.jpg

alltracman78
02-17-2007, 01:11 PM
Readings vary according to temp.

2-3 Kohms @ 68*F
Resistance goes up as temp drops, and down as temp increases.

If you have no resistance, it's bad.

Melchior
02-17-2007, 05:14 PM
Yeah... I figured it's bad.

Is there *any* way to replace just the temp sensor in the afm itself? or is it to risky to bother.

alltracman78
02-18-2007, 11:31 AM
I would replace the whole thing.
There should be AFMs available here and there.
Any 90-93 ST185 [except the homologation ones, CS/RC/GrpA] will work.
I don't know if any others will or not.

Melchior
02-18-2007, 08:53 PM
Got my hands on an st165, i'll give it a try. Research seems to show it works, only difference is an extra signal that the 185 doesn't use. We'll see.

Melchior
04-29-2007, 02:36 AM
Car was re-assembled today; the new MAF also gives code 24, but it reads fine via a multimeter.

I'm officially stumped.


Other things the car does that might help in diagnosing;

Idle seeks between 800-1000 very rapidly all the time;
Died while being rev'd and as it died the exhaust was blue/white for the last second or so (lots of smoke)

Other than that and a known bad turbo, the engine is good. Starts easily, good compression, has new plugs/wires/dizzy... etc..



Ideas?

toyotatuner
04-29-2007, 02:53 AM
i have a question regarding our AFM...how important is the resistance it gives out? meaning optimally would we want it to be at top end of the spectrum?(given in the EWD)

thought about this after workin with my old one and was able to adjust to whatever resistance i wanted. just wondering if that has any affect at all. hopefully this makes sense. lol

Melchior
04-29-2007, 02:58 AM
Well, they aren't supposed to emmit one constant signal; they are supposed to report a range of signals and each point in the range corresponds to different data.

In the case of the IAT sensor for example, as stated above, if it's at 68*, it reads between 2-3kohms. If it's higher, it reads lower, so at like 80*, it would read between 1-2kohms, for example. If the temp is lower than 68*, it would read higher.

You don't want it to stay the same, and there is no "optimal" point, just as there is no optimal point on a thermometer, or your gas gauge. They're just tools for measuring a fixed range of data.

toyotatuner
04-29-2007, 02:58 AM
this maybe a dumb question...but since u say its been 're-assembled' have u messed with any of the wiring? could there be something missing? i know that the afm sends a direct signal to the TPS or recieves. check and make sure that is happening.

Melchior
04-29-2007, 02:59 AM
I didn't mean to say it was re-assembled, I was refering to me puting the car back together.

it hasn't been re-assembled.

Gary
04-29-2007, 03:42 AM
1. Reset the ECU and check for the error code again.
2. Check the continuity of the THA wire from AFM to ECU.
3. Check the THA wire if it is grounded.

Melchior
04-29-2007, 03:51 AM
1. Reset the ECU and check for the error code again.

It was reset when the new AFM went in (in fact, battery had been out for 3 months anyway...)

2. Check the continuity of the THA wire from AFM to ECU.
3. Check the THA wire if it is grounded.

Will do this now, thanks for the advice

Melchior
04-29-2007, 04:14 AM
Oh joy; car just stopped starting.


Sounds like no fuel to my ears; fuel pump makes noise when tested. Man, what a bad day for my car :(

Melchior
04-29-2007, 04:58 AM
OMG, what a freaking day.


Fixed/found all my problems


Car not starting: Wire to dizzy from coil was REALLY corroded at the dizzy end; However the wire itself is less than 5 months old, leading me to belive the owner who replace the wires got a shitty wire. Replaced it, car starts on the first crank, idle is dead on 900, doesn't seek anymore.

AFM/IAT code 24: No ground on THA. BLAAAAAAAH. Never had to find a ground problem before. Also, I noticed my gauge cluster doesn't light up all the sudden; I think there is a relation.

So, basically, my Original AFM was bad AND the THA wire doesn't have ground. I wonder if there is a relation here?


So yay! major problems gone.

andy
04-29-2007, 05:27 AM
yo man, check the tail fuse. Also make sure your parking lights still work. If they dont, its your tail fuse. We just went through this with my friends mr2

Gary
04-29-2007, 06:10 AM
So, basically, my Original AFM was bad AND the THA wire doesn't have ground. I wonder if there is a relation here?


So yay! major problems gone.
Actually, the THA wire should not ground.

Melchior
04-29-2007, 07:50 AM
Oh. So then i don' t have a problem there.

I'll pull the gauge cluster tommorow, maybe i just have a loose wire. Actaully come to think of it, the stereo wasn't illuminated either.

Oh, and my parking lights work fine, but i'm gonna check all fuses tommorow anyway

Melchior
05-10-2007, 02:15 AM
Just as a follow-up to this, and in case anyone ever needs to know;

The st165 AFM WILL work fine on an st185. No codes, runs fine, no problems.