Injuneer

Did you check the pink wire for +12V, when measured to the black/white ground wire in the MAF harness connector?

Don 97 SS

Injuneer, I did and I would sometimes get 12v and other times not. My results were inconsistent. Then, again, I would occasionally get a blown fuse one the one that is in line with my MAF and the O2 sensor that even more complicated diagnosis. I may have more than one problem. I may have a short in that front, right bank O2 wiring that is creating or perhaps contributing to my problem. Pinpointing the culprit has been frustrating.

firstlast

i fixed it i just ran a wire to my air system fuse port, because my air system isnt there anyways

97LT4SS

Two months later and I still no luck fixing my P0100 MAF code, car just sits. So, yesterday I borrowed an Actron scanner which monitors the MAF current while the motor is running. The voltage fluctuated between 12-11.5v but then dropped to 2.4v within 5 minutes. SES light came on, motor still ran but very rich. Then as usual motor died and I could not restart, turned over a couple of times but then the battery died.

My question is could a weak battery cause the sudden drop in volts? Was under the impression that the Alternator supplied power to the car while running, right?

Guess my next step is to replace the Pink wire with a new one from the ENG fuse to the MAF sensor. Would rather not splice into my wire harness but what other options do I have.

Does the Pink wire supply 12v to or from the PCM?

Injuneer

The pink wire from the fuse to the MAF harness connector supplies +12V to power the electronics in the MAF. It does not have anything to do with the PCM. The MAF sensor puts out a variable frequency signal to the PCM.

Power goes to the PCM on pink wires from the PCM IGN fuse. That wire, at least for the 95's shown in Shoebox's PCM wiring diagram, splits in the harness and supplies the MAF as well.

Not sure how a scanner can measure the "current" from the MAF, since its basically an A/C signal. You then quote the results in "volts", not amps, so I don't see the relation? Also don't see how a scanner connected to the PCM can read MAF voltage, since the only wire that goes from the MAF to the PCM is the yellow signal wire to pin B19, and that wire operates at 5V without the engine running, and is typically around 4.3V when the engine is running, with variations, since its really just a "carrier" for the variable frequency signal from the MAF.

What a scanner reads off the PCM is the "system" voltage, and if you had a failure of the pink wire from the PCM IGN fuse, before the split for the MAF, the MAF would die, and the PCM would cease to operate, since it can't run at 2.4V. Sounds like the problem is in the pink wire leaving the PCM IGN fuse, before it splits to the MAF and PCM.

97LT4SS

Fred,

Are you saying I should splice into the Pink wire after it leaves the PCM IGN fuse or instead splice into the Pink wire before it enters the MAF? I'm guessing it's the later, if so, can I run a wire directly from the battery to the Pink MAF wire or should I tap into another 12v source?

The scanner was reading between 11 & 12 volts from/to the MAF and then dropped to approximately 2.4 while the motor was running. I'm learning as I go so probably not wording the problem correctly. SES light came on, the motor stumbled and then died completely.

Thanks again for your help,
Eric

Don 97 SS

Wow, Injuneer, what a fine response to his question. I never cease to be amazed from your knowledge of LTxs.

Anyway, I justed wanted to jump back in to say that I think (and pray) I may have solved my P0100. After following this and other archived posts on this and related probems I began to examine my wiring harnesses. I discovered a burned through harness that was touching my SLP shorties on the pass. side. The contact was so far down I could barely see it. I am refering to one of the harnesses connected to the PCM and passing to the left of the AC and going down the wheel well by #4&6 exhaust tubes that it touched. The contact burned through heat shielding tape and loom and apparently some hot wire that grounded on the headers (I think). I believe but am not positive this accounted for the blown 20amp fuse that served the MAF, an O2 sensor, skip shift thingy, etc. I probably should research and determine exactly what wires are in this harness, but haven't thus far. Can anyone tell me what wires are in this harness? I'd like to know for sure what I repaired. The burned spot is almost impossible to see or for that matter access to repair from above. Since access was so difficult I had to used a Q-tip with a dab of RTV to cover the exposed wire and then recovered the harness area with a new sheet of alum coated heat shielding cloth mat.

I've driven it a few times and no P0100 and other codes I mention this fix because this harness is so vulnerable that others should check this location if you have a P0100 and an occasional blown fuse. In my case the wire's contact with the coated heaters was sporadic enough to make the short hard to find.

97LT4SS

Don, couldn't agree more...Fred knows his stuff, that's for sure. I know the harness and area you are referring too, there's about a 1/4 inch of clearance. I originally did not use Random Tech's cat extensions so the incorrect wires used to power the rear O2 sensor eventually melted causing the 20 amp ENG fuse to pop. I've had a problem with the MAF throwing code P0100 since the headers & cats were installed in 2003. Wonder if the improper wiring and subsequent melting of wires somehow permanently damaged my wiring harness. Don't see why since I've spliced in the correct harness and the O2 sensors have worked fine since 2003.

Not sure if Fred remembers but he also talked me thru my ENG fuse problem back in 2003. Think I'll inspect the harness you are referring to Don one more time.

Thanks,

Don 97 SS

http://shbox.com/1/harness.htm Shoebox has an incredibly great pic of the harness loom section that I referenced.

From this pic of a 95, that loom section carries the bank2S1 O2 sensor, the engine ground wires, starter hot wire and KS. If this harness is the same for 97s then I must have had a burned 02 wire that grounded on the header and shorted the fuse that had my MAF, hence the P0100 in my case

*Knock on wood* I haven't had a P0100 or any other DTCs since I fixed that burnt/shorted wire.

97LT4SS

Don, that's great news. I on the other hand have re-checked my wiring harness and came up with nothing. Gonna start my search for a reasonably priced new Granatelli MAF sensor and go from there. Not sure what else too do at this point because my original GM MAF will not even allow the engine to start.

Not sure what this says about technology, because in the 15 years I have owned my other Camaro, 1971 RS Z28 M22 w/4.10's it has never had a problem or left me stranded. Let's just say I'm not a fan of OBDII and the dreaded SES light.

Later

firstlast

if your car is tuned the granatelli isnt a good idea, the reason they make horsepower as a bolt on (for cars with no pcm work) is that they lie to the pcm telling it that more air is going through it, so your pcm will give it more fuel. if your car is tuned it will work but a better choice would be another gm one

Injuneer

Actually, the Granatelli works just the opposite. The stock LT1 tuning is too rich in power enrichment (PE/WOT) mode, typically setting a target A/F ratio of 11.8:1. The Granatelli is altered to report less than actual air flow at the top end, causing the PCM to supply less fuel and (if you are lucky) lean the PE mode A/F ratio out.

But.... doesn't matter how it works. The point is still valid... the Granatelli is a poor (and expensive) substitute for a good tune with a stock MAF sensor.

97LT4SS

I honestly do not remember when I installed the Granatelli, before or after the incorrect O2 wires were installed. Is it possible that I damaged my original GM MAF when I was blowing the 20A ENG fuse back in 2003? I might have installed the Granatelli after installing the correct rear O2 Extension for the Random Tech Cats.

Sounds like a good time to purchase a new GM MAF and then see where I'm at. Where or who would have the cheapest GM MAF?

Thanks for the help guys.