'02 Impala 3.4L, 209.4k : P0102 Won't Go Away!

Colt Hero

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#1
Make
Chevrolet
Model
Impala
Year
2002
Miles
209447
Bought this car brand new in June 2002. No accident history; service history: just oil changes, brake pads, rotors, and of course intake gaskets where I replaced everything in the path down to injector o-rings back at 104k miles (2007?)

So I've had this code for quite a long time (over a year). The (original factory) MAF sensor had been cleaned three times with the CRC cleaner, but the code came back each time. Checked it with the OBD-2 reader and it came up "0.0". Had 5V at the sensor, so I replaced the MAF sensor. Code came back 2 or 3 times, still read "0.0" on OBD-2, so I got away from it for a while. A few weeks ago, I pulled the battery cable off for about 4 hours. Yesterday I finally re-checked OBD-2, and now I'm seeing values on the MAF, but the code is still there.

See attached for three successive OBD-2 data captures on the way to work in the morning: 1st capture was on secondary road on way to Interstate. 2nd was while ON the Interstate, and 3rd was on secondary road on way to place of employment (you can tell by speed, rpm, and miles since DST, which I still haven't cleared).

Can anything be gleaned from these data captures? I'm thinking I could have a partially-obstructed, or intermittently-obstructed exhaust (which is all original from factory). I've notice some "holding back" of the engine power on the interstate at times. As I hold the pedal steady, the car *seems to* lose steam at times, leading to me having to press the pedal down harder. I don't *think* I'm imagining this. Engine has also been externally-leaking coolant at a rate that requires overflow tank refill about every 5-6 weeks. If any of that coolant is *also* going through the engine, then maybe it's been slowing killing my CAT? I noticed the leak last year sometime ... maybe it's been close to a year now?
 

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nickb2

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#2
Since I see you are able to get some sweet live data, can you change the MAF reading from lb/s to g/sec?

I would like to see what that says when you floor it. You should observe a rapid increase from 4grams to 130grams before second shift (1-2nd).

I don't know what type of scanner/code reader you are using, but if only choosing the MAF pid, may help increase the baud rate at which it will read.


It looks like a excel spread sheet, so I am assuming this was taken from a elm327 maybe to your laptop or smartphone? Yes? No? If you are, can you tell me which software you are using. I may help in choosing better baud rates, changing pid values and such.

Reading pounds per second is not as precise as grams per second, and the time frame from WOT from 1st to 2nd needs to be quick and precise.

If you are not getting the expected values @ WOT, expect a clogged or restricted intake duct or air filter or exhaust. I am assuming the air filter is new on this old impala?

Another thing to look at is for crossed harnesses with things that generate induction/magnetism. Such as motors, relays, solenoids or ignition wires/coils etc. Sometimes, a harness that is close too to the one that houses the MAF wiring may give interference and give a wrong reading.

These tips come from alldata, but just the other day, I had a Chevy express cube truck in. We had taken the trans out to get it sent for overhaul right after the new year. Truck came back this week with a stall only in reverse.

A shyter load of codes came out of that one, so dealt with them the best I could to protect a co-worker who had completely forgot to connect the two read Ho2's and had squeezed the main trans harness cuz it was routed wrong.

I told my boss none of this. That particular co-worker has made a few mistakes too many these past months, he would have been on my boss's wrong side again.

Anyways, called the trans guy up who rebuilt the thing. He mentioned on these trucks, it is easy to have the trans main harness too close to the alternator, and the magnetic fields will do that sometimes. Anyway, I had the truck for a few days. I rerouted the trans main harness to it's proper place on drivers side of trans, where as before, other co worker had squeezed right at the top of the trans and could not budge the harness as it was jammed in the trans tunnel, lowered the trans support to free it and relocate.

Direct hit had a few guy's saying that a clogged radiator, or cooler lines could also cause this scenario.

SO I flushed the cooler and radiator as this truck has a aux cooler.

Long story short. I will never know if I fixed it with the cooler flush, repluging the o2's, or relocating the harness, but something worked.

SO when someone tell's you magnetism can affect a sensor, you better belkieve that, cuz I see that often, and no wonder you see that also on troubleshooting charts like the following snapshot.

Screenshot (1).png
 

nickb2

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#3
To hit home this more,

Like I said, I assume that was the intention. I also check crank sensors with my soldering gun. Has just the right hz to trigger a response or influence a such sensor. When you soldering gun is humming, you got a great induction going on and you will see that in real time on the scanner when you approach the offending sensor with it. 60hz is enough to create a large enough variation that the ECM may pick that up and create a false code.
 

Colt Hero

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#4
Hey nickb2!

Good to hear from you again! I haven't been here in a while. I see they re-did the website. Looks really nice! Very colorful, and not like all the rest.

Funny you mention the g/s units. I *had* it that way because the numbers are larger, but then my temps were in Celcius, so I switched it back. But if you just do the straight conversion, 0.03 = 13.6, 0.07 = 31.75, and 0.06 = 27.22. I don't have the scanner in front of me right now, but that's about what the numbers were.

It's a Harbor Fake Centech OBD-2 Handheld. Bought it last year. Might be discontinued at HF. This looks like it (at Amazon):
https://www.amazon.com/dp/B00GKOQA3G/ref=psdc_15707381_t3_B00GKOM66G

I'll try re-capturing tonight on my ride home with just the MAF. I'll have to remember to try "flooring it" on the on-ramp to the Interstate. Never drive that way, and I'm not sure how the car with respond.

Air filter is relatively new. Maybe two years? I'd have to check my records when I get home. But it's clean, not oily or anything like that.

I don't think I've got a harness issue with interference. All the wires are routed just as originally from the factory, but I'll double-check anyway.

One other thing I forgot to mention: Fuel range per tank is down at least 10%. Used to get over 500 miles per tank. Now I'm getting about 450, and I could check my records at home, but I'm pretty sure it's been trending downward over the last year or so.
 

Colt Hero

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So I took it to a LONG interstate onramp that is almost never used, stopped, then floored it. OBD2 reader recorded over 1000 points, but I had to let off the Gas well before that. Numbers started at 49 g/s and steadily rose to 128.8 before I let off the pedal, but I don’t think that happened from 1st to 2nd gear. I guess I’d have to dump the data to the computer because I can’t see any time stamps on the handheld

And my trip odometer was at 430 miles when the low gas message appeared, so it appears my tank mileage is around 480, which is *still* down, but not terribly (maybe 40 miles?)
 

nickb2

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#6
Oh, I see,

https://www.amazon.com/dp/B00GKOQA3G/ref=psdc_15707381_t3_B00GKOM66G

The spread sheet I saw was a few freezes downloaded to your pc for proper use.

I recommend you alot for even knowing how to do that. That means you have a larger scale of understanding than the average DIYR in regards to a analytical thought process to having a permanent fix to a temporary solution.

.

At least the amazon thing reads ABS and freeze frame and some limited live data.

However, I do recommend a elm327 of sort sort as you progress with me in your car/truck woes. You can buy a few for 15$ on ebay, slap a few in your cars, pair them to your phone, PC, laptop, even a few 4cpu tablets make a heck of a scanner in android form.

This can all be done at the fraction of what that cent tech thing does. Not to knock what you bought, but you will need a better and more sophisticated car at some point. . It will be good if you got ahead of the tech before it is to expensive to buy once the lobbyists get their brown noses into that.
 
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Colt Hero

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Here's the process I went through when searching for a new OBD-2 Code reader:

I still have an old Actron handheld I bought in 2000. It's this one (#9035) Just reads codes:

https://www.ebay.com/p/Actron-OBDII.../1824747439?iid=272967584266&rt=nc&opts=opick

It still works, but they changed the OBD-2 protocol sometime around 2006, so it couldn't read my 2011 Equinox. So I *thought* I'd "upgrade" to a laptop program, thinking it would give me more capability. That brought me to the ELM327 chip - which is used by various vendors to build their particular hardware device that connects to your laptop (to transfer the data from the car's computer to your computer). And then these vendors may also have their own software program(s) that put the data up on various splashy-looking displays. But then, I discovered, you've also got the "knockoff" or "counterfeit" ELM327 chips out there that some vendors have chosen to build *their* hardware device around. In at least *one* case, a vendor (SCANTOOL?) claimed their device (which used the counterfeit chip, I believe), could read more data than all the rest (ie: MS-CAN, and SW-CAN). I would've bought this tool (MX?) had it not been for all the complaints regarding the wireless interface. But if you look at the *wired* options (OBDPro, OBD2AllinOne, etc.), they don't support MS-CAN/SW-CAN, some are not updatable, some use "their own" chip instead of the ELM, and at the end of the day, they're not providing any more data/information than what I could get from a handheld.

So I went back to Actron, which has about a THOUSAND models out there! They won't tell you what chip they use, some cannot download to a PC, some have ABS but not for your model, some say they won't even READ your model (or they only will up to an older model year and they can't say if you'll ever be able to upgrade it). It's just a circus.

I got disgusted and just went down to Harbor Fake and bought their best model (with ABS). Paid about $80. Done. I can read codes again. I can record data. Good enough. Tired of all the runaround with all the other vendors.

Bottom line: I think all these devices read pretty much the same set of data, and a LOT of it depends on what modules are actually IN your vehicle, anyway. You're going to pay $150 for any of them, and get no real additional benefit. If you want REAL capability, you're probably looking at spending $1000 or more, but what DIY'er can justify that?
 

nickb2

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#8
Well, sure looks like you did your homework. And best of all about that is, you made an informed choice on what type of tool you needed for your purposes.

I just this week, picked up from my old boss, an Autel MS908.

Very sweet bi-directional scanner. Employee discount so to speak, should be out 500$. But for a guy like me, this will be a great tool to make sideline money.
Bi-directional, reflashing capable scanners like that come at a hefty price, when you add all the upgrades and such.

I had it on here in the forums somewhere. A scanner for sale, but no one wanted it. SO I bought it. It will be a great tool to make a how to video in the section here that jordanr put on you tube. I will be making one soon also. Maybe when the snow melts.

The maxisys 908 is basically a samsung tablet on steroids. I've been working with it for 8months now, always have that thing in my hands. Very tuff for a chinese product. I was extremely skeptical at first using this, being it was chinese. But I must say, surpasses anything out there right now. The very expensive snap on versus (virus) just sits there even if it has a scope for it. That thing sicks large for the enormous price tag.

A moderate DIYer could find a used one like the one I bought from my work ofr the same price or maybe less depending on last upgrade.

Anyway, enough about me and scanners, It is after all, my job and my main hobby. A passion I guess you could call it.
 
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Colt Hero

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Good deal! Looks like a 75% off discount!

But someone on Amazon mentioned that there are Chinese 'knockoffs' of the USA Autel version that won't update after one year? Could that be why you're getting that big discount? Is it a Chinese 'knockoff', and how do you know?

Amazon write-up says it has "programming" capabilities. What exactly does that mean ... that you can change "parameters" from some kind of fixed menu, or that you can actually change the *logic* in, say, the ECM? I would doubt they'd allow you to change the physical program (and I would think it's encrypted anyway), as that would open the door to potential liability (at least until they discovered the factory program had been tampered with).

I know the "Tuner" people claim they're changing the physical program, and I've even seen some hardware products that, I *think* replace the ECM wholesale (for high-end vehicles like BMW), but if this is, in fact, going on then the warranty is certainly voided (unless these things are only being undertaken *after* the warranty period expires).

Have you ever been able to actually *see* the program logic in any of these onboard computers? I would think even a Tech at a dealership cannot *see* the program logic, only replace it wholesale with an "update"...
 

nickb2

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#10
To answer you chinese question, I really don't know if I would have got a knock off. All I know is that it was bought from the carquest parts representative. The updated version, the elite 908 came from same guy. So I do know that for the past three years the boss has had it, not update problems.

And no, the "logic" or should be say, "algorythm" cannot be seen with common dealership hardware.

mazon write-up says it has "programming" capabilities. What exactly does that mean ... that you can change "parameters" from some kind of fixed menu, or that you can actually change the *logic* in, say, the ECM?
Yes to this question, the 908, whatever it's form, can reflash certain cars without a j2534 interface. That would include BMW, Volks, toyota and a few others.

As for some europe models, ecu can be modified with code. The launch software helps you do that. The autel also has a section for such events you need to modify a line or two of code. This can be done with the VAG tool. The Autel has a VAG emulator which in essence is a VAG.