Timberwolf

I had an SES light set earlier this morning which turned out to just be a fluke O2 heater circuit code. I cleared it and it never came back...but while I had the scanner on there I checked out all the sensors and the MAF was reading 0.0 gm/sec...and yes, the car was running.
Now, if the MAF were truly dead, I should have a MAF code showing, right? And also, wouldn't the A/F ratio be all screwy because the car woudn't know how much air was coming in, just how much was coming out (via the o2 sensors)? Seems like it would skew the heck out of the PE vs RPM tables....

thoughts? This is an OBD2 LT1 car by the way.

zlightning

It would use the map sensor if the maf died.

Timberwolf

but it would still throw a maf code, right?

Red on Red WS6

I think if the MAF sensor goes out it goes into speed density mode. That is why your AF is still ok, but yes you should get a code. Are you using Autotap? If so try closing the program and running it again. I notice sometimes of a couple of sensors hang up. I reset the program and all is good.

Timberwolf

Nope, it's a snap-on scanner I have at work.

Injuneer

Were you only checking it at idle? The PCM checks the rationallity of the MAF sensor reading to make sure its within 25% of a value table that reflects (I think) rpm and throttle position. I'm not sure if it makes that check while the engine is only idling. Might only make it when the engine is under some sort of load. If it makes the check and the MAF reading is too far from the table value it will set the code.

What you are seeing ( "0" ) would indicate the MAF +12V supply circuit was still OK, but that the sensor is not outputting the frequency signal. OBD-II has 4 different codes for 4 different MAF problems.

Timberwolf

ok, I need more help!

Still having problems with the 96Z. I don't get it. the thing ran excellent for the last 300 miles since I bought it... driving for hours at a time. Then all at once an electrical gremlin goes through it.

Last night, it ran like crap. Code said CKP circuit failure, and CKP 18x/24x circuit out of range. So I replaced the crank sensor today. started and idled fine. Took it for a spin and it had what felt like 4 cylinder power. Checked the scanner and the MAF was in fact reading...averaging around 250 gm/sec was all. Not 2 minutes later, the SES light was back on. This time it said "IC (injector control module) not toggling or grounded" and it set the two CKP codes again. I checked out the engine data, and not only is the MAF not readinging again (regardless of load or engine speed), but the MAP is showing a 0.0 reading as well. The o2s seems to be swinging well, though one seemed lazier than the others. Did I mention I had a code yesterday morning saying "o2 heater circuit failure" as well? I cleared that and it hasn't come back...but the other three or four codes have been showing back up religiously. On a whim I repklaced the MAP since it was the next cheapest part in line and it made no difference, still a zero reading.

So do you think the PCM has gone haywire? Maybe a loose ground somewhere or perhaps burnt power wire touching ground?
Even when there was no SES light showing today, the car ran like a 4 banger. Real slow! Trying to rev in park or neutral seemed like the motor was sluggish. It took way to long to sweep the tach, and it would stop at 5k.

I need some thoughts here from you folks. This thing ran like a champ, looks great, but now has a mystery electrical bug. I'm on the verge of trading it for something carbed.

Injuneer

Sounds like a bad ground. Very unlikely all those sensors and parts would fail simultaneously.

What code list are you using? Try the one on Shoebox's website.... it is LT1 specific.

Timberwolf

I wasn't comparing to any list...I was going by what the Snap-On Scan Tool told me. Codes were something like P0155, P0335 and p0335, and P1361.

Injuneer

The problem is that a scanner will contain "generic" code listings. Again, if you want the absolute correct code descriptions for your car, use Shoebox's list. They are similar, but they are not the same. But if you prefer to go with the Snap-On stuff, that's up to you.

Timberwolf

I checked shoebox's code list and they were the same basically, though slightly less specific then the snap-on descriptions.

Injuneer

OK.... if you want to argue about the codes, I don't have the time. Use yours.

Timberwolf

wow injuneer, what's wrong with you? I'm not arguing... just stating how I got the codes. why would I argue with you? I'm confused as to how or why you would be offended by what I said

For example, for the P0336 the snap on scanner said "CKP circuit 18x/24x out of range" and shoebox's site says " Crankshaft Position (CKP) sensor circuit performance"

Thus the reason I said the snap-on was more specific. I didn't know you would be offended because I didn't praise his list. I wasn't saying his list sucked or anything of the sort...

The first thing I said was I didn't use a list, I went by what the scanner said. So you suggested I compare notes, which I did. I then stated that I had compared them and that they were slightly less specific.

I guess I don't understand the hostility