MAF & SES

[xlr8us]

I have been getting a SES light on my 2000 GP 3.8 for some time now. Had it scanned, and came up with "P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency". Changed the MAF sensor, drove it for 3 days (about 250 miles), light went out for a day. Came back on next day, and went out that night. Had it scanned again and came up with same code, and a "Coolant temp not reaching thermostat temp. I had the codes reset while the SES light was out, and it came back on after about 20 miles. Could I have gotten a bad MAF sensor? Or could something else be kicking this P0102 code?

BTW 102,000 miles... Thanx

[GTP Dad]

Anything is possible. The sensor should be guaranteed so take it back. They are very expensive and they should be willing to take it back or at least exchange it since you have a SES since you changed. You may also have a problem with you PCM that is not reading the MAF correctly but try changing the MAF again to see what happens.

It is also possible that something else is setting the code but it's doubtful.

[jay69dogg]

99 Grand Prix GT 3.8L 85,000 miles
I'm having the same issue. I installed a refurb MAF sensor yesterday. It was refurbed by CarDone. Ran the car for about 20 miles with no issues. When I started the car again, the RPM's fluctuate afrom 700 to 1500 then stabilize, then the SES came back on. The RPM's start to fluctuate again after I rev it. The fluctuating RPM's has been intermittent. I'm getting the P0102 code as well.

I've been measuring voltages on the MAF connector.
Connector disconnected from the MAF, yellow wire: 5V
Connector connected to the MAF, yellow wire: Had 2.62V, now 11.5V w/ the engine running
Connector connected to the MAF, yellow wire: 10.3V, key ON, engine off

I''m wonding if 2.6V on the yellow wire is normal. With it at 11.5V, the RPM's are fluctuating.
Chilton's talks about reading the MAF frequency using a scan tool. I don't have one so I tried reading it with a DMM. My DMM has a frequency counter function but I'm not picking anything up on the yellow wire. I' don't know if I can read the frequency this way.

Anyways, I'm interested to see what the normal voltages are on the MAF when it's connected. I'm wonding if I have a bad MAF or a wiring issue.

I also seen in Chilton's that the TPS could cause a MAF issue. They say it should read ~4.8V at full throttle, I'm only getting 4.11V. Could this be a possibility as well. Also, my car only has ~ 13.9V while running. Thats a little low.

[xlr8us]

Originally Posted by jay69dogg

99 Grand Prix GT 3.8L 85,000 miles
When I started the car again, the RPM's fluctuate afrom 700 to 1500 then stabilize, then the SES came back on. The RPM's start to fluctuate again after I rev it. The fluctuating RPM's has been intermittent.

I'm having the same fluctuation with the RPM's. Cruising at 55 to 60, let up to coast, and the RPM's go from 1500 to about 800 then back to 1500. This doesn't happen all the time. I have 8 more days to get this fixed for NYS inspection.

[GTP Dad]

I am sorry I don't know the voltages but I really think both of you need to take the MAF sensors back to where you got them and get new ones. Fluctuation in the rpm area is generally due to a problem with the MAF sensor. When they get dirty you can have this problem and when they go bad a similar problem develops. The possibility that both of you got bad sensors is not as remote as it may seem.

[xlr8us]

Well, I replaced my MAF again and the SES light is out. It's still bringing up the same code "P0102". We passed NYS inspection, but the car is running like CRAP! At any RPM, driving or stopped, the engine seems to just lose power. At idle it has stalled a few times, and accelerating or cruising it seems to buck. Do I have to disconnect the battery to reset things, or do I have another bad MAF? Or is this deeper that that?

[GTP Dad]

Are there any other codes in the computer. The bucking issue can be due to misfires that the computer is not registering or a bad injector. It could also indicated that there is a problem with the Crank or cam position sensor. I would look deeper into the problem, however, if you haven't changed plugs and wires lately that is where I would start. I would also disconnect the battery to reset everything to see if anything changes. The computer needs to learn that there is a new MAF in place and this should allow everything to reset to default. I hope this helps.

[xlr8us]

"P0102" is the only code I'm getting. Well, I disconnected the newest MAF and it seems to be running fine. I'll disconnect the battery and re-connect the MAF and see what happens. I think I got another bad MAF! BTW, the SES light is back on (before I disconnected the MAF)

[richtazz]

make sure you have the SES reset with a scan tool. The old school method of unhooking the battery doesn't work on OBD-II vehicles and your computer may still be bypassing the new sensor. Also, you may have a bad wire going to the MAF or a TPS out of range, which will confuse the computer as to what fuel adjustments need to be made.

[BNaylor]

An odb-ii PCM can be forced into re-learn mode and all DTCs cleared and MIL/SES light reset by disconnecting the positive connection to the battery and then holding ignition switch to engine start position for at least one minute. I've run ths procedure on numerous Grand Prixs, Regals and Olds Intrigues, etc. It's a modern day hot rodders trick.





Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[xlr8us]

Well after several weeks of diagnostics, it was determined that I not only got ONE bad MAF, but the SECOND one was bad also (only worse)!! Installed the third one and all is well again. Thanks for all the help and suggestions.