[FIXED] 02 GM 3.1 403-5 DTCs

By snapping the throttle can you get a maf reading over 15 pounds a min? 1 pound a min seems high to me at idle i would expect to see about .5 to .6 pounds at idle with warm engine

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StepSide88 wrote: My gauge was a 60 lb test with 10 lb marks and 3 tick/hash marks.
the needle moved between .5lbs idle and 2lbs or maybe slightly more at WOT as best I could read while driving with the gauge laying outside against the windshield on the pass. side.

What sort of MAF readings are the normal range for this beast?

I misspoke about that windshield reading. That was when I was reading the fuel pressure during WOT ( which was steady @ 50 psi)

The exhaust back pressure I am fuzzier on and didn't record that on video.
I'm clear it didn't over 3psi at all

I'm going over the data recording from the EVAP drive cycle and will try and spot the three throttle blips that are called for.

The Service $01 SAE 0X10 MAF read 13.48 lb/min if that helps.

At this point I plan to try and run a cleaner (fewer missteps) Drive Cycle and see what that says.

I was quite pleased that the computer cleared the 403 and 405 codes with out my telling it to.
That at least indicates that part of it is healthy.

Here's a throttle blip a few mins after the 6.5 minute section of the EVAP Drive cycle.

Oops thats not the MAF

bottom of one top of the other

After the 45 min cool down after the drive cycle I checked and got this;

Monitor Status Report
Name Continuous Available Complete
Misfire Yes Yes Yes
Fuel System Yes Yes Yes
Components Yes Yes Yes
Catalyst No Yes Yes
Heated Catalyst No No No
Evap System No Yes No
Secondary Air System No No No
AC Refrigerant No No No
Oxygen Sensor No Yes Yes
Oxygen Sensor Heater No Yes Yes
EGR System No Yes No
MIL Off
Number of Stored Codes: 0
US State: OR
This vehicle is ready for emissions testing.

I literally had not see the "Ready" until I was in here posting the copy/paste from my program.

I did have to change the battery before starting this AM. but it has been acting poorly due to long periods of diagnosis.
I'm not ready to declare this fixed yet , it is nearly ready for a freeway on ramp though.

Wow that graph looks very suspicious at the end your map and maf show 3 throttle snaps but your tps only shows 1 but the 1 that the tps shows the maf barely reported at all this could be a issues with your obd2 adapter lagging what adapter are you using?

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Ben wrote: Wow that graph looks very suspicious at the end your map and maf show 3 throttle snaps but your tps only shows 1 but the 1 that the tps shows the maf barely reported at all this could be a issues with your obd2 adapter lagging what adapter are you using?

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Here is a look at todays run.
Time window is 180sec in this view
the blips are after the 2 min idle .

This OBD adapter and program is called OBDWIZ.

Hmm didn't load.


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Were all 5 of them wide open throttle the last 2 are only showing 50% on the tps but the maf and map seemed to report close to 100%?

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Can that software log a 2 min test drive?

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Ben wrote: Were all 5 of them wide open throttle the last 2 are only showing 50% on the tps but the maf and map seemed to report close to 100%?

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I believe the TPS is correct. I have yet another one from this AM's drive I'll try and grab a shot off when I review it.

Ben wrote: Can that software log a 2 min test drive?

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Twenty mins if you want...

So I'm trying to use the P0405 vid to sort out my P0404 but thats a Ford and mines GM. No controle valve solinoid its digital (see #2 below)
1.1a Typical engine control components - 3.1L engine
1 Manifold Absolute Pressure sensor
2 Digital EGR valve
3 Intake Air Temperature sensor
4 Mass Air Flow sensor
5 Powertrain Control Module (inside air filter box)
6 PCV valve
7 Camshaft Position sensor (not visible)

OK I have a digitally controlled by the PCM inside the air filter box

But the wires coming out of the EGR connector an makes a hard turn for the other side of the engine and disappears into the bundle/s that emerge over by the Alt.

I can dig if they decided to send the wires the long way around but without a pin out or something reference I'm struggling to see how I sort out the voltage issue cause.

And my secondary issue with it is it's still refusing to accelerate and seems to not want to shift between 2 and 3 at higher rpms.
No problem below 15mph.

So I would suspect some sort of vacuum leak but why no codes for something like that?

Did you remove and clean the carbon on the egr valve? What is the year make and model . What type of log file does your software save I'm mostly interested in the data from when it won't accelerate can you get a good file that includes map ,maf, tps, speed, o2s1,load ,rpm and maybe commanded and actual egr posistion

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It saves TDL or CVS files

Its a brand new EGR valve.... I didn't test it.

I guess I could make a video of the strip charts running as well as shots of the DashBoard .
Not all the PIDs are supported or maybe I just haven't figured out how to get them functioning while recording (they don't work when not recording either) but Commanded EGR isn't one that reports any data.

If you have a way to read a CSV file I'd send that in a heart beat.

Yes email to agardiauto@gmail.com

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Ok for anyone following along after viewing the file at wide open throttle driving down the road (under load) were only seeing 50 g/s passing by the maf the oxygen sensor is going full rich (as it should) indicating this acceleration issue is not fuel related we disconnected the maf to see if there was any improvement since this made no difference were going back to the exhaust test with a lower range pressure gauge to get a more accurate reading

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All right, I got a 15lb gauge and ran the test. 0
Back to garage test hose and removed the Schroeder valve.

Turns our THAT was why my readings were so low when I tested with the 60 lb gauge.
So when I reported 3lb on the exhaust back pressure that was wrong.

Now with a clear line I need the 60 lb test gauge.
WOT immediately pegs this 15 lb so easily 20-exhaust back pressure.

I'm relieved. I was worried I was gonna have to pull out my uncles old oscilloscope and learn how use it next...

Unless theres something else to test I'll order a Converter and report back for a final fixed.

I really want to thank you guys for the help and pointers.
I am coming out of this with more knowledge ,new tools, one of which I got invent and possibly refine, further testing is needed.

Ok good. you can disconnect the exhaust behind the cat to verify it's the cat that's plugged and not the muffler but I usually just bang on it to make sure there's no pieces of the cat that went into the muffler also make sure there's no kinks in the exhaust pipe(I've seen people back into stuff that kinked the pipe at the bend right in front of the muffler). Also this stresses the importance of accurate test equipment when doing any test !

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Well I'll start removing the Cat at the back and test the pipe on back half first but just having a symptom and diagnosis agree at this point feels like a win after all this time.

Checking a new tool like the pressure gauge didn't occur to me until I had to address the inconsistencies I was facing.