PO101 Mass air flow.

[Boomer]

Make

Chevy

Model

S-10

Year

2002

Miles

168,000

Engine

4.3

Guys I keep getting this code coming back. The top reported fix seems to be replacing the MAF sensor. The engine seems to run fine so I’m guessing the problem is the sensor. Since my scanner does live data, I figured I’d look at it and upload here so you experts can see if anything looks amiss. I hate throwing parts at things.

 

[grcauto]

I would need to see the trims, load, maf, tps and rpm together for a couple minutes.
You flashed through the trims in a couple seconds but I did see the LTFT were at 13 and 14 which means it's running lean.

 

[Boomer]

Understood. I'm not sure what file size can be uploaded here. I was at idle as I"m sure you figured out. 4 days ago, I had PO101, PO131, PO137, and PO151 (low voltage oxygen sensor circuit codes) I cleared the codes and those did not come back on with the exception of 101 today. The truck has been driven daily. My round trip for work is approximately 32 miles. I don't know if that stuff means anything to 101 coming back but, I didn't want to leave out the info. Unfortunately, I can't show all the data simultaneously. As you can see from the screen size.

 

[paulo57509]

PO101 - Have you tried cleaning your MAF sensor?

 

[Boomer]

PO101 - Have you tried cleaning your MAF sensor?

I have taken it out and cleaned it a couple of times with the cleaner spray you buy at Autozone. I haven't done it recently. I could try it again. I suppose that wouldn't hurt. It didn't look dirty when I did it before.

 

[NickD]

Another problem with these things, the PCM requires a start voltage of at least 8.5 volts so that its microcontroller gets a proper POR or power on reset. If not the program counter is not reset to zero randomly reads code that also was not properly reset. Another cause of this lower voltage, starter kicks on, and can get a surge current of close to 800-900 amperes. Problems can be a little corrosion on the battery terminals, grounds, ignition switch that drops an extra volt or two, or a partially sulfated battery.

Common cause of this is no battery caps on a so-called maintenance free battery, hate this marketing term, electrolyte still evaporates leaving the top of the plates bone dry. Bad for consumers, good for battery replacement sales.

Putting a scope with memory across the battery terminals shows if this voltage is dropping below 8.5 volts, won't find this in any shop manual, tell you to use an ohmmeter, good way to fry it.

Getting random codes periodically is a sign of an erratic POR. Most alternators are grounded via their frames and using the cheapest oxidizing aluminum they can find. Another cause of low voltage. Another problem is lack of electroplating connectors, instead of our good EPA helping to solve problems with the waste, banned it in the USA, and if this job is exported say to Mexico or China, really don't do a very good job. EPA never solves problems, just fines you or shuts you down.

 

[Boomer]

View attachment Aug 8 139.MOV
Ok, I cleaned the air filter and the MAF sensor. I used CRC brand MAF cleaner. I have now made 3 trips back and forth to work and the light came back, on the 3rd trip. I made a little longer recording. I wasn't sure how big of a file I could upload so I made 5 separate videos.
View attachment Aug 8 139.MOV

 

[NickD]

Besides the component as the cause of a problem can also be the connector, in particular the material used, before Nixon, one 35 buck ounce of gold could plate over 100 square feet, only metal known to man that is corrosive proof. So each male or female connector pin was just a tiny fraction of a cent.

Connectors are a convenience to make it easy to replace a component, but also a major cause of problems in particular what is called a dry circuit, lacks any kind of arcing current.

In your mass air flow sensor have two wires. one is exposed to incoming air, other, the reference is buried and protected. So any coating of the exposed wire acts as a thermal insulator to give false readings. This is one problem, other is the connector, all PCM voltages are a mere 5 volts and practically all are "dry" circuits.

Put in another way, if you want problems, we got problems. A spread female terminal in the connector or a tad of corrosion can be the problem for connectivity. Connectors have to be attached straight in, any angle can spread that female, and at times, this is not an easy task when you have to stand on your head to attach these.

Ha, my naive wife thought we were talking about sex when dealing with connectors, plumbers had the same problem.

 

[nickb2]

Ok, I cleaned the air filter and the MAF sensor.

Hmm, just a thought. Since I notice you cleaned the air filter, I must ask, a stock filter or not?

cuz I have seen a few of these "P" flow filters cause these problems. Put back stock intake and oem filter, mass air flow goes back to normal. There is a tune you can get to fool the ecm, but say goodbye to good gas mileage.

Anyways, that was just a thought. Another good way to fry a sensor with a "P" flow shyte is those Kn style wet filters, gunk up the sensor, and as I used to do, would clean the sensor with brake parts cleaner and then use shop air to dry it. Well, little did know back then, I just fried that sensor and caused repeat comeback just for this same example code.

If all connections and air intake back to stock assuming it is not doesn't fix it, you probably need a new MAF and plz dont buy the cheap ones, in this area of sensor, you want high end or OEM at least. My experience is 28 now going on 29 yrs in this field, and I say this alot, this is where you dont want to cheap out on. Point in case, had a camry in the other day. client didnt want to pay for oem maf.

Code kept coming back. Had another camry in lot, with a evap problem, was waiting a few days to get a canister for it. So i took the MAF off that car and put it in the clients car and sent him on his way. Funny thing is, client never came back. So now I had to explain to my boss why we had to buy a new toy MAF. Boss wasnt happy. I said I dont care. That is one client we dont need if he wont listen to head tech.

 

[nickb2]

As an after though, I have kept that maf sensor. So if I ever see that client, I will put back in his own MAF. He will come back again and again. SO I told my boss, hey, see, not so bad. Then boss rolled his eyes at me. He says gosh, you are incorrigible.

 

[NickD]

Yet another minor problem with these things is positive crankcase ventilation. Crap the bypasses the piston rings into the crankcase. In carb days the return of the PVC hose was into the base of the carburetor directly into the intake manifold.

But with fuel injectors, for whatever reason, the law makes insisted the PVC should be returned to the intake of the throttle body where this crap can build up on the throttle valve causing it to stick in particular with TBW, on the MAF sensor, face of the injectors, and also under the intake valves.

Would think if they had any brains, but definitely a shortage with the EPS would direct it into the catalytic converter where it wouldn't cause any internal image damage. Its also exponential in action, putting this crap back into the engine builds up on rings, causing more junk to form in the engine.

 

[Boomer]

Besides the component as the cause of a problem can also be the connector, in particular the material used, before Nixon, one 35 buck ounce of gold could plate over 100 square feet, only metal known to man that is corrosive proof. So each male or female connector pin was just a tiny fraction of a cent.

Connectors are a convenience to make it easy to replace a component, but also a major cause of problems in particular what is called a dry circuit, lacks any kind of arcing current.

In your mass air flow sensor have two wires. one is exposed to incoming air, other, the reference is buried and protected. So any coating of the exposed wire acts as a thermal insulator to give false readings. This is one problem, other is the connector, all PCM voltages are a mere 5 volts and practically all are "dry" circuits.

Put in another way, if you want problems, we got problems. A spread female terminal in the connector or a tad of corrosion can be the problem for connectivity. Connectors have to be attached straight in, any angle can spread that female, and at times, this is not an easy task when you have to stand on your head to attach these.

Ha, my naive wife thought we were talking about sex when dealing with connectors, plumbers had the same problem.

Looks ok here, NickD.

 

[Boomer]

Hmm, just a thought. Since I notice you cleaned the air filter, I must ask, a stock filter or not?

cuz I have seen a few of these "P" flow filters cause these problems. Put back stock intake and oem filter, mass air flow goes back to normal. There is a tune you can get to fool the ecm, but say goodbye to good gas mileage.

Anyways, that was just a thought. Another good way to fry a sensor with a "P" flow shyte is those Kn style wet filters, gunk up the sensor, and as I used to do, would clean the sensor with brake parts cleaner and then use shop air to dry it. Well, little did know back then, I just fried that sensor and caused repeat comeback just for this same example code.

If all connections and air intake back to stock assuming it is not doesn't fix it, you probably need a new MAF and plz dont buy the cheap ones, in this area of sensor, you want high end or OEM at least. My experience is 28 now going on 29 yrs in this field, and I say this alot, this is where you dont want to cheap out on. Point in case, had a camry in the other day. client didnt want to pay for oem maf.

Code kept coming back. Had another camry in lot, with a evap problem, was waiting a few days to get a canister for it. So i took the MAF off that car and put it in the clients car and sent him on his way. Funny thing is, client never came back. So now I had to explain to my boss why we had to buy a new toy MAF. Boss wasnt happy. I said I dont care. That is one client we dont need if he wont listen to head tech.

Hey Nick, yes buddy. Stock air cleaner. The filter I believe is a FRAM. The orange border on it. Nothing has been changed recently that would set off alarm bells. Thanks for the advice on the MAF should I need one. I'd like to test whatever I can before just replacing a part.

Did the video of live data help at all for any of you guys?

 

[billr]

I only looked at the first one. The ratio of "download" time to "view" time is too poor for me to want to look at the rest. If I use the MAP/rpm/IAT of the first one to calculate MAF, it does not correlate to what the PCM reports; but that means little as I am merely repeating the calcs the PCM does to set the code. You already knew the MAF reading is off, correct?

Do you have a meter to read frequency of the MAF signal?

 

[Boomer]

I only looked at the first one. The ratio of "download" time to "view" time is too poor for me to want to look at the rest. If I use the MAP/rpm/IAT of the first one to calculate MAF, it does not correlate to what the PCM reports; but that means little as I am merely repeating the calcs the PCM does to set the code. You already knew the MAF reading is off, correct?

Do you have a meter to read frequency of the MAF signal?

Thanks for the reply, Bill. Yes, I have a Fluke meter that will read frequency. Our power was out from the time I got home from work last night until sometime while I was at work today so, I didn't make it back here until tonight.

Yesterday (Monday) when I was driving to work, the SES light, went off. It has stayed off through todays trip home. I did NOT reset it after taking those videos. I wasn't expecting that. I guess time will tell if it comes back on.

I suppose the light coming on and the code setting indicates the MAF reading being off? I'm not a pro mechanic so, I am not familiar with doing those calculations in my head. I can still measure the frequency if you think I need to.