Not another P0102 code! Test your troubleshooting skills!

[Cheezer_Holio]

Different story here than most people so I guess I'm looking for some guidance.

I have a 2004 Impala SS 3800 SC with 108,000 miles. 100% factory stock, no major engine work ever conducted (T-stat, coolant flush, serpentine belt, regular oil changes and maintenance since new).

Driving 60mph road load when the car began to stumble. Vehicle would buck and surge during acceleration. No codes. Did not have time to diagnose and drove other vehicles for a couple months.

Last week drove the car about 10 miles until MIL illuminated with code P0102 MAF low frequency. Cleaned with CRC MAF cleaner - no change, verified ground on B terminal, battery voltage on C terminal, installed new Duralast MAF w/ battery disconnect - no change, cleaned air filter and honeycomb - no change, cleaned IAC valve - no change.

Now the odd part is that the MAF reports normal frequency between 2-3000 Hz and normal g/s while driving during closed loop and the vehicle runs fine (verified with OTC Genisys while driving). This leads me to believe the MAF sensor is ok. As soon as it warms up and goes closed loop the engine immediately begins to idle poorly and will stall. g/s mass air flow reported sometimes drops to 0 for exended periods and has spiked over 360 g/s during 40mph steady state road load.

Engine may stall if I touch the wiring harness correctly. I will begin further electrical tesing tomorrow (probing for wire breaks, bad connector). Any hints, tips, ideas? I would really like a wiring diagram for this circuit. Where is the ground, why is closed loop the determining factor? Are the odds better the Duralast part was junk or I have a wiring problem, or something else? What should I be chasing here? I HATE troubleshooting by throwing parts at it. Any help much appreciated.

[rustydogy]

po102 code maf low freq, Could be caused by low voltage to sensor too, By what ,and how you have trouble shooted ,I think you may have stumbled on the problem your self, You said by messing with wiring harness it would stumble and die check those wires , I think you will find a bad wire,i will look around on Alldata and see if I can find a wiring diagram for you, I think you get this part done then the closed loop thing will come in line

[Levithan9]

Ok, as a certified tech, let me give you some advise.

As you have a scanner capable to read live data, do this simple test:

Bring up Calculated Engine Load on the scanner

Bring up MAF Sensor g/ps

Take the car for a test drive. Turn off all loads...ac, blower motor, radio. From about 15mph, step on the gas...and don't let off until your about 60-70mph.

Then when you can, look at your 2 readings. Your Calc Eng Load should have gone to AT LEAST 85%, and your MAF g/ps should have gotten in the neighborhood if 152. Plus or minus 10% of that number is ok.

This test usually tells if the MAF is reading properly through all the shifts. A lot of times, I can see that the MAF won't go above what it should.

A easy way to check if a MAF sensor is reading good is to take the displacement of the engine .....which in your case is a 3.8L. Now, take 3.8 and times it by 40, which gives you 152. That's the ballpark figure your looking for the MAF to get to under a W.o.t operation.

Let me know what you get, and I'll help you as best I can.

[Cheezer_Holio]

Ok so I did some more testing starting with the load test. Again the car operated ok during open loop. I waited for closed loop and conducted the WOT run described earlier. I snapped some pictures of the recorded run. I maxed at 83% load (very close to your prediction) and the MAF varied from 0 g/s to 363 g/s during that time. You can see the progression of the run in the following images:







So I began to test for a break in the wire. I pierce probed the wires at the base of the connector and touched the wiring harness again to see what caused the readings to fluctuate. To my surprise the ground was always grounded and the 12V supply was always constant at 14.6 volts (unless the vehicle dipped to almost stall at which point I figure the alternator did not have enough RPM to make 14.6 volts).

My suspicion turned toward the MAF sensor itself because every time I touched the connector the car would die. I believe touching the wiring harness caused a slight pressure on the sensor and there is a short inside the sensor itself. And whenever I touch the sensor with my finger the output frequency fluctuates wildly (verified with DVOM on Hz setting). And I mean a very very light touch. If I barely rest a finger on the MAF sensor body the output signal immediately changes and the car surges and knocks. I am going to try an OEM sensor instead of the Duralast junk but the dealer wants $387 for the MAF, OUCH! Thanks for the help guys, I'll check back for any responses and follow up if the sensor fixed the issue.

[Cheezer_Holio]

***Update for anyone following this thread or maybe someone will find this in a search years down the road.***

I ordered a new GM Original Equipment Manufacturer AC Delco brand MAF sensor and installed it in about 5 minutes. Amazon.com carried the exact OEM part shipped to my door in two days for $200 less than the dealer wanted! Immediately at first startup the signal was perfect and the car drives great. The longest part of the whole ordeal was taping the original wire loom back on where I was probing for wiring shorts or breaks. Lesson to take from this post: Some things you should not cheap out on, MAF sensor is one things. And I shouldn't really say "cheap out" because the Amazon deal was less than AutoZone's Duralast part and it still was not the cheapest option (versus used part from a yard, other brands to try, factory rebuilds, etc). I would simply recommend getting a brand new OEM MAF if you really suspect it is your problem.

Thanks to everyone for the help and suggestions and good luck to anyone with this problem in the future.

[shorod]

Glad to hear you found the problem. Thanks for following up, that's much of what makes these forums work!

-Rod

[SleepyHead98]

Just looking at the graph of the MAF you can tell its bad. You can even tell if it is bad with a simple multimeter. The MAF volt output should change/vary exactly with the revs of the engine. More air needed(which is what MAF measures) should be more/less volts. They should change at the exact same ratio/speed. So if you slowly increase revs, the multimeter should slowly change with the revs on the MAF output volt.

[maxwedge]

Too add, I've gone thru 2 reman Cardone maf's in my 2003 Lesabre, all failed about in 1 year and were replaced on warrantee.