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Old 05-01-2014, 07:27 PM   #1
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Help reading Scan9495 tables?

my cars been running rough lately and the only code it throws is the AIR. can anybody help me analyze these files? car is stock except magnaflow muffler and k&n filter. also im not sure wheres the best place to upload these .csv files... any help is appreciated
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Old 05-01-2014, 08:30 PM   #2
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Re: Help reading Scan9495 tables?

Whats the code#? It could be that the AIR system has a leak.

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Old 05-01-2014, 09:57 PM   #3
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Re: Help reading Scan9495 tables?

The only code for the AIR system is DTC 29 for the AIR pump control circuit. Most common problem is a blown fuse for the pump. PCM turns on the fans full time in response. Replace the fuse. If it blows again, unplug the AIR pump, then put the new fuse in. Fuse won't blow, pump won't run, but you won't get the code. Does not affect how the engine runs if that's the problem. Only thing the AIR pump does is run for the first couple of minutes after startup, PCM in open loop, to reduce the emissions from the rich startup A/F ratio, and help the cat heat up faster.

Exception would be if the circuit set the code because the wires are shorted and the pump is running all the time. Then the air it blows into the exhaust screws up the O2 sensor readings in closed loop, making the PCM think it's running lean, and it adds fuel the engine doesn't need. But if that was the case, I would also expect to see codes for "system lean".
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Old 05-01-2014, 10:25 PM   #4
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Re: Help reading Scan9495 tables?

it doesnt seem to me like the AIR pump would be causing the engine to run the way it is now... its a little bogged down and i know theres a tranny issue (55mph+ vibration, worse when you let off the gas. think its my driveshaft but im not positive.) anyways my AIR pump has been unplugged for awhile now. What should i do to go about finding my problem if its not throwing any codes?
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Old 05-02-2014, 09:27 AM   #5
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Re: Help reading Scan9495 tables?

Run a data log using Scan9495 and post it on an FTP site where we can download it and take a look at it. There are no diagnostics for drivetrain vibrations. There are codes for auto trans problems, which would included excessive slippage.

As already explained, the AIR pump being unplugged does not cause the code. It's more likely the fuse. Do your fans run all the time? They should only run with the A/C or when coolant temp exceeds 226*F.

You need to add a "Signature" with basic info about your car - year, model, engine, trans, and any major mods. Go to the red task bar at the top of every page, left click on "UserCP", on the dropdown click on "Edit Signature". Enter the info in the field that appears and save.
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Old 05-03-2014, 03:32 PM   #6
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Re: Help reading Scan9495 tables?

in park
Upload Files, Easy: Quick File Post

one is in in park and one is driving around the block, cant remember which is which but im sure it looks obvious to you guys
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Old 05-04-2014, 10:20 AM   #7
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Re: Help reading Scan9495 tables?

Quick look at the idle log shows the Cell 16 (idle cell) long term fuel corrections are maxed out at +25% on both sides, and the PCM is using the short term fuel corrections to add a total of +50% fuel on the left side and +30% fuel on the right side. Either the MAF sensor is not reporting correct air flow, or something is causing the O2 sensors to report a major lean condition. Do you have any exhaust leaks BEFORE the O2 sensors? Are there significant levels of misfire on both banks?

MAF sensor reading is a bit on the low side. Have you ever cleaned the MAF sensor?

The second file only has 32 seconds of driving, and a lot more idle. Not sure how much we can learn from that. Like Cell 16, the other "driving" cells are maxed out at +25% (BLM - 160) on both sides, and the short terms are adding even more fuel. The throttle position is jerking all over the place.... reads "0%", 1/10th of a second later 23%, then back to 0 in the next frame. Was that the way you were operating the throttle?

May be tomorrow before I get a chance to look these over in more detail.
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Old 05-04-2014, 01:40 PM   #8
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Re: Help reading Scan9495 tables?

Quote:
Originally Posted by Injuneer View Post
...Exception would be if the circuit set the code because the wires are shorted and the pump is running all the time. Then the air it blows into the exhaust screws up the O2 sensor readings in closed loop, making the PCM think it's running lean, and it adds fuel the engine doesn't need. But if that was the case, I would also expect to see codes for "system lean".
In neither scan was the lean condition occuring for the 50 seconds needed to set codes 44 or 64. And for code 55, when the fuel enrichment flag is set, the BLM's are sitting at a nice 128 level. Perhaps he should remove the fuse for the AIR pump. The line from the pcm to the relay could be shorted to ground and that would keep the pump on all the time the ignition is on which would set code 29.

Edit: NVM I missed where he said the pump was unplugged.
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Last edited by GaryDoug; 05-04-2014 at 09:26 PM.
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Old 05-04-2014, 03:35 PM   #9
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Re: Help reading Scan9495 tables?

ok guys heres an update. those readings were taken with a new mass airflow sensor. afterwards, i cleaned the old one (had to find torx) with electric parts cleaner and put it back in. just like the new one. so i returned it to the store. while i was there i decided to rent out a fuel pressure tester real quick. I only tested at idle, no taping to the windshield or anything (tags are out anyway ). it read around 32psi at idle and i know it should be about 10psi higher. so i didnt want to leave empty handed and bought a new fuel filter. it seems to have made things MUCH better but I still have hesitation issues. Thats where I am now. as far as the exhaust leak goes i think i do have one on the passenger side, maybe a bad gasket? whats the easiest way to locate it, with a squirt bottle? i have a new scan file from earlier, just at idle. If i need to record while driving under certain conditions or anything just tell me what to do and ill run the scan.

Fuel filter replacement, recorded at idle.
towards the end i reset the iac with the program. cant remember if i tested actuators before or after i stopped scanning so be aware.

in what i believe to be unrelated, on another note, my vehicle still vibrates at 55mph+, the worst being at 55. Its most noticable when letting off the throttle, but still prevalent otherwise. i was hoping it would be a symptom of poor fuel delivery, but i am not so lucky! anyway where would you folks start looking? could a bad flexplate replacement at a shop have caused that somehow?
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Old 05-04-2014, 07:13 PM   #10
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Re: Help reading Scan9495 tables?

I took a drive to a friends house so i brought my laptop along with me to run a scan. pretty average driving, nothing over 45mph. here is the log. ill run another on my way home.

Average drive through town
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Old 05-04-2014, 08:54 PM   #11
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Re: Help reading Scan9495 tables?

alright here is one more, same drive back but a bit more liberal this time.

Drive #2 (drive 1 backwards)

let me know what else I should look into, the engine still stumbles and hesitates, mostly from a dead stop. i think i got up to 60mph this time.
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Old 05-04-2014, 08:55 PM   #12
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Re: Help reading Scan9495 tables?

Fans are coming on at about 140F. Is this PCM modified/reprogrammed?

Both BLM's are still stuck way high at 160 for the whole run. So far though, it sounds like the low fuel pressure is the problem. I missed the part where you said the AIR pump was already unplugged. Whatever the problem, it is affecting both sides.

As for the vibration, I would check the transmission mount.
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Last edited by GaryDoug; 05-04-2014 at 09:29 PM.
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Old 05-05-2014, 02:18 AM   #13
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Re: Help reading Scan9495 tables?

i know nothing about the PCM. Personally ive never touched it. its probably not the original. can it be something other than fuel delivery?

ill have to check the tranny mount..does shoebox have a good guide for that?
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Old 05-05-2014, 12:24 PM   #14
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Re: Help reading Scan9495 tables?

Quote:
Originally Posted by GaryDoug View Post
In neither scan was the lean condition occuring for the 50 seconds needed to set codes 44 or 64. And for code 55, when the fuel enrichment flag is set, the BLM's are sitting at a nice 128 level. Perhaps he should remove the fuse for the AIR pump. The line from the pcm to the relay could be shorted to ground and that would keep the pump on all the time the ignition is on which would set code 29.

Edit: NVM I missed where he said the pump was unplugged.
My comment regarding the "lean" code was not specific to the two data logs. It would seem that the system might have run lean in the past, while the various cells were building their LTFT's to the 160 level.

As I noted, I only took a quick look at the files, and the one he called "in park" I assumed was the idle file, only looked at the beginning to see when it went into closed loop (206 seconds, O2's ready, coolant 150+ deg = correct), and then to the end to see if the Cell 16 LTFT's had changed. I missed the fact that it was not in "park", and was being driven.

That being said, when it goes into PE mode, Cell 15 has not been fully developed (nor has Cell 11) so the LTFT's are still near 128, 130. But look at the O2 sensor readings - they start out OK, but then they drop to 0.111V and below on the left and 0.111V to 0.524 on the right. You would expect to see high 0.800's/low 0.900s in PE mode. But there are transitions where he's getting on and off the throttle, making the readings of limited value. Maybe the new file with more extended, and hopefully more stable operating conditions are logged.

The flag shows no reset during the log, so I would assume that DTC 29 is a stored code, and that is why the PCM was not commanding the fans on in the "in park" log, in response to an active code. Looking closer at the second file from the 5/3 post, the fans are on, possibly in response to an active DTC 29, but then they turn off at 153*F.

I still have not downloaded or looked at the additional files.
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Old 05-05-2014, 12:38 PM   #15
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Re: Help reading Scan9495 tables?

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...... so i returned it to the store. while i was there i decided to rent out a fuel pressure tester real quick. I only tested at idle, no taping to the windshield or anything (tags are out anyway ). it read around 32psi at idle and i know it should be about 10psi higher. so i didnt want to leave empty handed and bought a new fuel filter. .....
Fuel pressure at idle needs to be measure both without and with the vacuum compensation line attached to the fuel pressure regulator. Without the vacuum line connected (cover the end of the line to prevent a vacuum leak) the pressure should be 43.5psi. GM accepts a pressure within the range of 41-47psi. Attaching the vacuum line should drop the rail pressure proportional to intake manifold vacuum, so a drop of 8-10psi would be acceptable, leaving your pressure in the low 30's. Was the 32 psi with or without the vacuum line hooked up?

On the left side, you are adding 50% extra fuel. That means without the LTFT's and STFT's the injectors are only supplying 66.7% of the required fuel. For this to be totally the result of low fuel pressure, your pressure would have to be about 20psi (20/43.5)^0.5 = 0.67

If you just look at the right side where it is adding 30% extra fuel (injectors supplying 76.9% of required fuel, the fuel pressure would have to be about 26psi.

I don't see low fuel pressure being the problem, if you are measuring a higher pressure.

The O2 sensors are telling the PCM it's running lean. Possible reasons:

FALSE LEAN CONDITION:
-faulty O2 sensors, or wiring
-exhaust leaks before the O2 sensors (did you remove the AIR plumbing or just unplug the AIR pump?
-misfires
-incorrect valve adjustment

TRUE LEAN CONDITION:
-low fuel pressure
-plugged injectors
-MAF under-reporting air flow
-air leak after the MAF sensor (torn elbow, elbow not fully on throttle body)
-large vacuum leak(s)

But we're looking for something that will affect BOTH sides of the engine.
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