I made a very big mistake..

Hello all, I made a very big mistake. Against my better judgment, I threw parts at my car to fix a CEL that will NOT go away. I heard of ScannerDanner from an EricTheCarGuy video and watched a video of his regarding MAF sensors, specifically, Chevrolet MAF.

He said in that video not to just throw parts at a car..

Anyway, I got a P0102 code for 'low frequency' on my Innova 3100RS when I plugged it in when the CEL first appeared. Upon closer inspection of the pigtail, I noticed a small tear in one of the wires connecting to the harness. I put liquid electrical tape on it and the problem seemed to go away. Well it came back, so I spliced in a new pigtail I picked up from the junkyard. Code came back, so I put a new MAF sensor in, car seemed to drive REALLY well for approximately 25 minutes, I parked it and then went for a walk. Started it up about 30 minutes afterwards and waddya know, code reappeared! Only this time, car no longer drove as nicely as it did before. Now, it jerks and stutters once again when I try to shift gears, it sounds really nasty (think of what no muffler sounds like when in 1st gear) and I don't know what else to do. I'm assuming this has something to do with the electrical wiring, thing is, I don't know where to begin to look or what to look for to fix. Please help. 

Car is a 2007 Chevrolet Cobalt SS (naturally aspirated) manual transmission 2.4L Ecotec engine.

Hello. 

Could be a sensor (and circuit) which is good, but is measuring out of threshold.

Can you post some PID's ?  MAP, MAF, TPS; ECT. Also freeze frame for that code.

Hi there, sorry for the delayed response. I'm a very below average DIY'er, so please excuse any incorrect/irrelevant information I may relay to you.

MAP is 10 (inHg),
MAF is 0.19 lb/min,
TPS is 24.7%,
& ECT is 145 degrees F.

I did take photos of all the information relayed on the scan tool when I hit the freeze frame button, so if you'd like that, just let me know and I'll upload that as well.

Hi,

Maf reading looks low to me.

Yes. Please post the whole picture.

With a P0102 most likely you have a bad sensor ground. Test harness side of connector unplugged. Yellow wire is signal wire, should have 5v. Black is the ground, should have .1mv or less. Red is battery voltage. Do test with key on engine off KOEO.

here are the photos from the scanner 

Hi, thanks for the reply. I'm assuming for this, I need to use my multimeter, right? I'm a below average DIY'er and I've never really used a multimeter before, so please excuse my ignorance.

When I do this test, I need to plug my red lead into each of those ports on the harness, right? And where do I plug the black lead into? Is anywhere on the engine okay? Again I've never done this before, so please pardon my ignorance

Yes, use multimeter. Black probe to good ground on engine. Use red probe to test each wire. Do not push probe into female ends of connectors. Gently touch each end. Make sure multimeter is set to DC voltage setting. Test battery voltage first to make sure you're on right voltage setting. Touch red probe to battery positive. Should read 12v.
Now with KOEO test each wire of MAF harness side female connectors not male sensor side. I suspect you'll have 10v on the black ground wire. That's where the problem is. Where ever that ground wire connects to the engine or ground buss it's not making good contact. A wiring diagram is best to have if not you'll have to trace the wire back to it's connection. You put on a new pig tail are you sure you wired it correctly?

Where is a good ground point on the engine? Can I stick the black lead anywhere I want on the metal surface of the top? Also, with the Cobalts the battery is located in the trunk and not inside the engine bay.

I'm going to insert a paperclip into the back ends of the wires, not from the front where it connects to the MAF sensor. And from there, I'm going to attach alligator clips because my leads don't have very long terminals.. Is there anything else I need to know? Or do?

Also, I'm absolutely certain I spliced the harness in correctly. I crimped the new piece with butt connectors prior to cutting the old pigtail off, and then I deliberately made sure to connect each piece of wire correctly, first by stripping it and then crimping it, one at a time.

Any solid metal on engine.

I'm not a fan of paper clips but be careful not to damage connector.

If you have a good ground you'll have 12v on the red MAF wire.

There isn't a red MAF wire, there are five wires that supply power to the MAF sensor, they are (in order) tan wire, tan with a black stripe wire, black wire with a white stripe, pink wire with a black stripe and the yellow wire.

When I tested the black wire, I wasn't able to get a reading. It just flashed a minus sign next to the number values and didn't do anything. I really tried to wiggle the paperclip gently as well, still nothing. There were at least two wires that did not display anything similar to the black wire, the yellow wire on the end I think flashed a 4.95 reading, the tan wire on the opposite side I think flashed a 12.73 but unless I really wiggled the paperclip in there, it just flashed a 4.95. It was the three midddle wires that didn't seem to display any readings

5 wire is a MAF/IAT unit.
Yellow is MAF signal
Black/White is MAF ground
Pink/Black is 12v power
Tan/Black is IAT ground
Tan is IAT signal
IAT is an Intake Air Temperature sensor

MAF
Yellow = 5v
Bk/W = .1mv
Pk/Bk = 12v

Get a "T" pin from your wife. It's a sewing needle with a T head. Don't use the paper clip they are to big.

Hi guys.

Remember to post freeze data you mentioned.

Hi there, I did post pictures (8 in total) but it did not allow me to. I think the file size was too large. I'm going to manually enter in all the data, hope you don't mind. I can upload the photos one or two at a time if you'd like, I just don't want to clutter this thread up too much. Thanks again for your help

P0102
Mass Air Flow (MAF) Sensor
Circuit Low Frequency
DTC Severity 2 of 3

Fuel Sys 1 = OL

Fuel Sys 2 = N/A

Calc Load = 7.5%

ECT = 145 degrees F

STFT B1 = 0.0 (%)

LTFT B1 = 2.3 (%)

MAP = 10 (inHg)

Eng RPM = 1228

Veh Speed = 0 (mph)

Spark Adv = 3.0 (degrees symbol)

IAT = 82 (degrees F)

MAF = 0.19 (lb/min)

TPS = 24.7 (%)

Run Time = 3 (sec)

Command EVAP = 0.0 (%)

Fuel Level 23.5 (%)

Warm-up DTC Clr = 0

Clr Dist = 0 (miles)

EVAP_VP = 0.0 (InH2O)

BARO = 27 (inHg)

CAT Te 11 = 280 (degrees F)

ECU Volts = 14.343 (V)

LOAD Value = 18.4 (%)

EQ Ratio = 0.839

Rel TPS = 14.1 (%)

Ambient = 70 (degrees F)

TPS B = 24.7 (%)

ACC Pedal D = 20.4 (%)

ACC Pedal E = 10.2 (%)

Command TAC = 18.4 (%)

Your data indicates low MAF g/s. At .19lb/min that's 1.4 g/s. You should have at least 2.4 g/s or around .3lb/min at idle. If this reading was with your old MAF, it needs to be cleaned. With a new MAF, it's a wiring problem. You had wiring chaffing prior you may still have it on the ground wire.

The - on you multimeter is reverse polarity. If you meter is auto ranging you should have gotten a value.

You have to have the three values I gave you. If you don't have them you have a definite wiring problem.

Take some time and practice with your meter and always insure you have a good steady ground.

Post the values of you get them.

Hi, so I just measured the values again, and they are as follows

tan wire, I got a 4.94
tan with a black stripe, I got a consistent minus symbol
same with the black wire with white stripe, I got a consistent minus symbol
pink wire I got a 12.21
and yellow wire I got a 4.95

for all of these measurements, I stuck the black lead onto the metal surface of the engine, and I probed using the red lead, albeit this time, I used a T pin and I made sure I stuck it all the way in. I re measured again to see if I got consistent readings, and I did. Not sure if I did this correctly, I apologize if I didn't. I also don't have a very good multimeter, it's a $20 MasterCraft that I got from the local parts store while it was on sale.

The three wires you're most interested in are the MAF wires. Pink, Black with White and Yellow.

Good, you have power 12v on the pink and 5v on the yellow. You should have .1mv on the Black White. If your meter shows no voltage numbers and is flashing the - sign I believe on the MasterCraft that is saying no voltage. If the meter has a "mv" or "m" setting in the DC range, switch to that and see if you get anything.

If you have a test light, attach the test light lead to a 12v power source then touch the point of the tester to the tee pin on the black white wire. Your test light should light up. If not the black white ground wire is open and you need to find the break in the line. The ground is controlled by the engine computer. If the ground wire is good you may have a computer problem.
You can also test that ground by plugging the sensor back in, tee pin the black white ground wire, start the engine and see what reading you get.

I'm going to go test that again, this time using your advised setting. I'm assuming it's the 200m and not the 2000m, right?

I don't have a test light, do I need one? I do have one or more electrical shorts that are drawing power from somewhere in my car that I haven't fixed yet. I can find those with my multimeter, right? Or would it be a good investment to purchase a test light for that?

Use the 20 setting on the DC scale. I suspect you have up to 10v on that ground wire.

If you get a test light. Attach the lead to a good ground then touch the probe end to the black white ground. Do this instead of the reverse I told you earlier. If the test light lights up you have a short. You should have no more than .1mv on that ground.

When you're posting a photo from the chrome Browser, mobile version you only need to select go to editor if you don't see the word attachments in black box with red lettering. 

I've taken a screenshot to show how I do it from Android. Also don't worry about it "cluttering up thread space" as the saying a pictures worth a thousand words goes great here in this industry. 
Even photos of the wiring job work you did & the surrounding area are helpful. Sometimes more is better when it comes to information as it can be helpful in more than one way. 

if you have access to Amazon you can click on the links  

I'm going to add some photos to show you where to click and find a good or see what good test lights are out there. 
 The Lisle test light can be found or similar ones at auto parts stores  I like the OTC one as I have multiple ones in multiple boxes for various types of auto work I hate moving certain tools around box to box or bag to bag so I bought a few and have them in multiple storage locations. 

Also in the Amazon store there's clickable links that take you to T-Pins. I swear by T-Pins or sometimes if I don't have one handy I'll break the wiring adapter set out as I have alot of connector heads for various types, sizes, etc  How much you Want to spend on those connectors is limitless, literally! I purchased the KIT from AESwave.com. First 2 items in this link are great for wiring testing especially if you plan on getting into more DIY Auto, helping friends, learning more. Here's the direct link to scannerdanner's page on AESwave.com 

www.aeswave.com/cart.php?m=product_list&...tIds=&venID=&stream=


That was cool as I haven't used the new copy, paste function of this web forum since they redid it. 


 





 


Also checkout the Autoranging multimeters others mentioned as well. Sure it doesn't come overnight but with the satisfaction you'll get doing the work yourself not to mention the money you'll save on shop labor you'll come out money ahead. 

1 hour of shop labor saved can get you a decent test light, backprobes and a good Autoranging multimeter  

After you save a few more hours or even make some helping friends you can get a test lead kit which even has a resistance meter dial. Those come in handy for countless things