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I did measure the pin 9 on the EEC with the MAF disconnected, or with the MAF wire pulled from pin 9, and I always get 5.7V. If that's supposed to be signal ground for the MAF sensor, that is odd. But it does drop to 0 as soon as I connect to the MAF sensor.

Also, I measured the pin C on the MAF sensor itself with A and B connected to +12V and GND, but nothing on C and D, just to see what that pin goes to (0).
 

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The floating to 5.7V is occurring right at pin 9 of the EEC with nothing connected to that pin (the call is coming from inside the house!). Looks like the wire going from pin 9 on the EEC to pin C on the MAF is OK, as it runs the test light with no problems. Same with the wired from pin 50 from the EEC to pin D. In fact, I ran the engine with pin 50 pulled from the EEC and measured the same 0.88-0.9V on the wire for pin 50. It varies as I open or close the throttle, though I can't tell how smoothly using a digital meter.

So something's going on inside the A9L itself to cause a shift of that MAF ground, and maybe the same thing causes it to freak out when it sees actual MAF signal. Time to start looking more closely at the A9L internals?
 

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you are very confusing

is there voltage on the PIN 9 WIRE when its disconnected from the maf and ecm??
 

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or

is their voltage on the ecm PIN 9?

just answer one at a time, everytime you throw more weird tests you muddle everything
 

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Do you have a moates qh or some way to see the ecm? If not buy one or I will sell you my breakout box. The test you are trying to run are useless if you cannot see them from the ecm. You can see the source but not the return to the ecm.
 

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The pin 9 on the A9L itself sits at 5.7V with nothing connected to it.

I do not have any EEC test jigs, so I can't easily see any particular signal without taking the connector apart and pulling a wire. How much does a breakout box cost?
 

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take take the pin 9 wire, and attach it to a body ground, just to see if the maf makes a signal with engine running, just a proof of concept

no to find the voltage.....

if you have voltage on the sensor ground internally in the ecm

you have

-open within the SHARED sensor grounds in the ecm
-poor ecm ground, not chassis ground,,,,,, pin 40,60 anywhere to the terminal point, under the washer bottle is the location i believe

to test this

one lead at pin 40 then 60, the other lead battery negative, with ecm powered up

also take a sensor any one, like ect or act, tps, UNPLUG it and check for voltage drop on the SIG RTN

you need to home in on the restriction
 

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QH will not help here

installing a breakout box, may falsely repair a bad connection

so NEITHER is helpful in this case

continue with finding the open on the ground
 

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Took some time to understand the words you wrote, here's my interpretation.

"""
take take the pin 9 wire, and attach it to a body ground, just to see if the maf makes a signal with engine running, just a proof of concept
"""

Did this before in a couple of ways. Connected MAF pins B and C together, and then tied to ground lug on car body. Engine only runs with pin D disconnected from harness, but measuring pin D on sensor shows 0.88-0.9V, and varies with throttle opening.

"""
no to find the voltage.....

if you have voltage on the sensor ground internally in the ecm

you have

-open within the SHARED sensor grounds in the ecm
-poor ecm ground, not chassis ground,,,,,, pin 40,60 anywhere to the terminal point, under the washer bottle is the location i believe
"""

Looking at the A9L board directly, the MAF RTN, pin 9, is not shared with any of the other sensor grounds. I chased down the wires going to pins 40 and 60, and they are terminated with lugs that are solidly screwed to the body. Pin B on the MAF is attached to one of these.

"""
to test this

one lead at pin 40 then 60, the other lead battery negative, with ecm powered up
"""

Are you asking for a continuity test or a voltage measurement here? I did both; continuity shows less than 1 ohm, 0 volts drop from pins 30/60 to ground points.

"""
also take a sensor any one, like ect or act, tps, UNPLUG it and check for voltage drop on the SIG RTN
"""

These signal returns go to pin 46, and, again, are not shared with the MAF RTN.
 

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When i state power up the ecm

Continuity tests are not done, that is a given, you dont perform cont tests on live circuits

Therefore you perform a voltage drop test on the power ground, 40, 60 like i said

Also while you are at it do it at pin 9 on the ecm

The ecm must be powered up

When testing the ground lug, you must test the wire going to the ground lug, as well as the eyelet and lug

Did you test one of the sensor’s ground?
 

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Obviously, I did the continuity tests with the battery disconnected. But as you said, a single strand of wire can show good continuity, which is why I also did some current tests by running a test light through these wires, and measuring the voltage drop between the EEC pins and the ground lugs. So far, all the test show I have solid ground connections going to pins 40 and 60, and solid power connections from the EEC relay to pins 37 and 57.

With key on again, SIG RTN from the TP, EVP, ECT, and ACT all show 0V. The VREF showed around 5.1V. If it had been 5.7V, I would have suspected leakage into the MAF signals, causing all the problems I'm seeing.
 

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well if you are confident through all your tests that the power and grounds are sound

you conclude that ecm has 5.7volts on the maf rtn

therefore the ecm is faulty, you can replace it with a good known

however, the question is tha,t was the maf faulty or did the wiring cause the failure

also i hope you used an incad test light and a not LED
 

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I used a high powered LED, which should draw about 1/2 amp. It's high enough to detect poor connections, but not too high as to risk blowing out drivers in the EEC.

I kind of suspected the problem was within the A9L from the way it didn't run the engine, but the SD ECM did. I'm not sure where I can get another A9L to try with. So until then, I'll have to revert to SD.

Thanks all for their assistance on this.
 

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you can check the a9l and maybe fix it
 

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Late follow-up.

I got another A9L off of ebay, and installed it. Ran and passed KOEO, so I cranked the engine, and it started and ran, poorly but it ran for longer than 1 second! First thought was there was something wrong with my first A9L. But the engine sputtered to a stall, as it was running badly, as was expected of a "new" computer working with an unfamiliar engine. Before long, I noticed smoke coming up from the area where the harness entered the firewall. There was some popping sound as well, so I pulled the battery cable off as quickly as I could.

I spent a couple days taking the harness apart, trying to find a short, and the nearest thing I could find was one of the connectors for the AIR solenoids looked kind of flaked. I wanted to continue diagnosing this, but did not want to burn up my new A9L, so I installed my old A9L in place. Hooked up battery, turned it on, no smoke or crackling. Cranked the engine, and wouldn't you know it, it ran, again poorly, but did not die after 1 second. I have no solid idea WTH is going on, but I'm guessing something in the wiring harness was shorting, but I could not find it. I applied a lot of e-tape around connections for the power and ground wires in the harness, and put shields around them where they could contact objects.

I've been driving it around for a couple of weeks, and I think the (old) A9L has learned to work with my engine, as it's running better when cold, and its idle settled down to about 800 rpm. Now I'm wondering if I should install the "new" A9L again to see if sparks will fly again.

Again, many thanks to all who provided inputs; they definitely increased my knowledge of this thing.
 

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not sure

but smoke may indicate a blown fusable link in that part of the harness

there fusable links in the harness
 
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Yes, those were the first things I checked. There is one right at that part of the bundle of wires, and they were all making connections.

Now that it's running "normally" again, I will try to run the KOER test again.
 

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Yes, those were the first things I checked. There is one right at that part of the bundle of wires, and they were all making connections.

Now that it's running "normally" again, I will try to run the KOER test again.
I would not rely on a visual inspection of a suspected blown fuse

measure for voltage drop

I have never seen smoke come out of the same device twice

once it comes out, it is done

i would just replace to be safe, and find the cause of the high current condition

direct short ground or shorted load........
 
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I actually did continuity checks from the EEC connector to ends that I could reach with my LED light, so the fusible link was carrying at least 1/2 amp. I'll admit I didn't beep out all the wires, so I will do that this weekend.
 
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