TATurbo1981

Hello LS1Tech.
I've visited and used this site many times, but this is my first post. Thanks to all of you for sharing your knowledge.
I have a P0102 DTC code on my 1999 LS1 which is showing symptoms I have not been able to find in ANY other P0102 thread or documentation anywhere in my hours of research.
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I've been through the P0102 troubleshooting in the 1999 F-Body Service Manual. Those troubleshooting steps have gathered a lot of information, but lead to no solution.
The engine is a used 1999 LS1. It's prior history is unknown. It was just recently swapped into my 1981 Trans-Am and has had this code since initial start up.
The harness and PCM were purchased as a package from Swap Specialties. Both appear to be a 2003+(GRN/BLU) pair.

I'll try to list everything I've tested and tried. But, I'll start with the strangest symptom:
When MAF Gr/Se is observed via PID's with my simple scan tool, it shows 2.32 g/s...Constantly. At idle or part throttle (no WOT observations were made) AND also w/engine running and the MAF unplugged ....the reading from the scan tool shows 2.32 Gr/Se. Engine off, key on the MAF Gr/Se shows 0.

MAF sensor connector shows 5v on yellow signal wire(when unplugged), 12 on the Pink + wire, and the ground checked out OK using Digital multi meter.
Engine off, Key 'on, MAF plugged in, the MAF Signal wire shows around .400 volts and 100hz.
Engine running, MAF Frequency(Hz-kH) and voltage vary with throttle position, as expected. Frequency increases to 3-4 kHz(3000-4000Hz) at part throttle.
I've checked the frequency and voltage both at the MAF connector AND Pin 31 at the PCM harness. The same expected voltage/frequency changes on the signal wire show at both ends of the wire (MAF connector and pin 31 of the PCM.

I've observed the same P0102 and 'stuck' 2.32 g/s reading with multiple MAF sensors AND two different PCM's programmed by two different sources. (The Harness/PCM retailer, and a second PCM flashed with a known working 'tune' by an acquaintance. .
Aside from swapping those parts, and testing the individual wires with my DMM, I've also:
- Verified the pins at the MAF connector against the Service Manual
- Verified the MAF sensor wire is going to pin at the PCM (pin 31) (continuity test in Ohms via DMM shows '0' resistance).
- Used a different, old MAF connector to wire the MAF separately (puling power and ground from another source AND replacing the Frequency/signal wire at pin 31 with my 'new' separate wire.
- Engine seems to run 'OK' with MAF connected or disconnected. (No change in idle, only tested in garage). I presume this is because its running off MAP readings because the PCM thinks the MAF signal is bad.
- There are no other codes and readings from other sensors (o2, MAP, IAT) appear to be accurate as presented in the scan tool PID's.

I think that knowing where the 2.32 g/s value is originating or how/why the computer is coming up with this constant MAF g/s reading might be the key to finding the cause.

It's almost as if the computer is just completely ignoring the MAF sensor and the 2.32 number I see is just some default value? The Service Manual says the DTC is set when MAF Hz show as < 10hz for > 1 second. But, my DMM shows a lowest reading of 100hz (Engine off, key On). Could there be a set of conditions where the PCM is just 'ignoring' what it see's on the signal wire? In a manner where the MAF Gr/Se would just show on a scanner with some 'default' value?

For more detail on my car and/or insight into the history/series of events leading me here, you can check out the last page of my build thread at:
http://transamcountry.com/community/...?topic=69897.0

Thanks in advance for your time and consideration!

-Tom
King of Prussia, PA

TATurbo1981

Thanks to all the people who took time to read over this...It was a weird presentation, so I'm not surprised I didn't get any replies. I was able to figure out the problem and the circumstances that lead to the unusual presentation. I'm posting all this info here in case some else gets stuck in this P0102 vortex like I did. Specifically, the 2.32g/s MAF reading. I couldn't find reference to that anywhere I looked.

Long story short...
My MAF sensor was 'bad'. I should say my MAF -sensors- were 'bad'... I happened to have two, and used both of them for testing.

Long story long...
The most difficult and perplexing thing was that..When MAF was viewed via a medium spec 'automotive' Digital Multi Meter(DMM), it showed 'good' Hz and Voltage readings. While, -AT THE SAME TIME- 'MAF Gr/Se' viewed from a simple code reader scan tool, showed 2.32 constantly. This reading would not change. This observation was made with two different PCM's and two different MAF's.

After a bunch of research and testing I got recommendations to start over and be methodical.
I forgot my prior observations, and walked through diagnostic tests again. Using
the Service Manual documentation(again) , this time with a couple key changes:

1) I ran the car up to temperature before taking any measurements.
2) I set up my phone to record my DMM while I was inside turning the ignition switch to start the vehicle
3) I reset all codes on the PCM then, without turning the key to 'off' I set up my tools and fired it up...Warm...diag tools set up and under
observation from the first second.
4) And finally, being methodical, pausing to note symptoms at each step, and note recordings on each diag tool (observed simultaneously)

My phone video caught the first couple of seconds where the MAF showed as reading < 10Hz on the DMM. Being able to actually observe the problem occurring was encouraging and helped me move forward knowing the trigger for the P102 DTC was actually real and happening.

Why didn't I observe this previously?
Could be quantum physics related...Some things you can't observe because the act of observation changes the outcome. More likely, it was a combination of the limitations of my tools, limitations of my experience, and the unique sequence of events.

Here are some things I observed that confused me...

- It looks like once the PCM observes the P0102 he starts ignoring the MAF signal? I'm pretty sure once the PCM saw a bad reading
from the MAF, my scan tool would just show a default MAF G/S of 2.32.
For example: Check Engine Light (CEL) was 'off', but P0102 was a PENDING code (I didn't always check 'pending' codes which are listed separately
in my simple scan tool). And, the way MAF #1 was screwed up, he'd show very low Hz for a couple seconds. Then once the PCM stopped
'looking at the MAF', it would start showing good numbers. While the Scan tool showed a steady 2.32 'MAF Gr/se'
Sounds crazy, but I observed this on two occasions. "MAF #1" was a new, generic MAF received with my LS1 Swap harness.
On prior tests, the MAF was reading 'bad', but...by the time I got to the front of the care to view the DMM, it was showing 'good' Hz readings...because the PCM
had set the P102 as a Pending code.

- MAF #2 was completely dead. MAF#2 was an old AC Delco MAF. Probably original to the engine I had purchased. Banged up and old.
When I plugged in this MAF as a test see if symptoms changed, I got a different set of #'s, but still that stupid 2.32 Gr/Se
reading at the PCM.
I figured "Swapped MAF #1 for MAF #2 and the symptoms didn't change. Probably not a 'real' failed MAF." <-Wrong.

- The P0102 Code was not 'cleared' when the PCM was removed from battery power. I assumed once the PCM was removed from battery
power, things were reset. Probably a stupid assumption(as many are). But the code was definitely still there after PCM swaps tonight.
I suspect that, in at least one instance of my many swaps from the 2003+ GRN/BLU PCM to the 1999 RED/BLU PCM, I didn't go in and
clear codes. So, the P0102 was in there as a pending code unbeknownst to me. Skewing my observations and leaving that '2.32'
value presenting in the scan tool.

- Replacing the MAF, without resetting the codes, Did not immediately clear the CEL OR change the PCM's behavior of showing
just 2.32 gr/se for the MAF reading.
The way I read the manual, the MAF P0102 'diagnostic' performed constantly. <-Wrong.
With different readings on MAF#1 and MAF#2, and not knowing which to believe, I bought MAF#3. MAF #3 is a refurbished ACDelco
MAF from OER. Plugging in MAF#3, and checking the MAF Gr/Se reading in the scan tool showed No change in behavior. The
CEL stayed on, the P0102 remained, and the 'live' readings from my scan tool still showed 2.32.

How did I end up with two f'd up MAF's?
This whole thing started at the initial start up of my swapped in LS1. With the new (at the time) MAF#1 installed.
The P0102 came up pretty much right away. My first thought was:
"I have another MAF. I'll just swap out MAF#1 for MAF#2." <-Not a the best idea, especially if the wiring is untested/unknown.
There was no change in symptoms. Even after resetting codes a couple times, the CEL would come back on with a P0102.
What I didn't know at that early juncture was that the MAF Connector was not correctly pinned in the harness. I suspect that mixed up
input into the MAF caused too much voltage, or a direct ground, or some similar condition which hosed up the MAF's internal
electronics? Thus screwing up two good MAF's. What's weird about this is that the two MAF's appear to have reacted differently to this
incorrect wiring. MAF#1 still looked 'OK' most of the time. 100Hz key on engine off, Good voltage, varying Hz. While MAF#2 completely died. Showing lower voltage, low varying Hz, and '0' Hz Key on Engine off.

SOLUTION: The solution ended up being a simple one. Install a new MAF. Reset Codes, then start up engine. I know! I spent weeks trying to track this down.
Know that the scan tool reading could be the PCM ignoring the MAF AND that a MAF can fail in a manner that allows it to still show 'good' Volt and Hz
readings and you'll save a lot of time!