Computer issue?

Black Sun 5.0

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May 15, 2008

#1

• May 15, 2008

• #1

I spoke to my mechanic who is getting ready to put a bullet in my '90 GT. Apparently, the only way to be able to run codes or get the computer to come to life is by manually grounding some kind of signal return wire or something like that. Sorry, I wrote it down and left the info at home. Does this sound like it rings a bell with any of you gurus out there? Also, when the cluth pedal is depressed and released, my mechanic also indicated that the idle will fluctuate. Anybody?

 

HISSIN50

"How long does it take to get help in here?

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May 15, 2008

#2

• May 15, 2008

• #2

Knowing the issue or symptom would help (dumping codes requires connecting wires. Making the EEC come to life should not).

Idle fluctuations with respect to the clutch being depressed are not entirely uncommon. That's not to say the issue should be there however.

Good luck.

 

Mustang5L5

That is…until I whipped out my Bissell

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#3

• May 15, 2008

• #3

That kinda doesn't make sense. What do you mean by "Makes the computer come to life". The car wouldn't run period if it was dead.


Is the car a T-5 swap? Sometimes not plugging the NSS on the top of the trans causes probs reading codes

 

Black Sun 5.0

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May 16, 2008

#4

• May 16, 2008

• #4

What exactly is the NSS? Anyway, I spoke to my mechanic again, and what was specifically said was that if the sigal return wire was not manually grounded, they could not get data, read, or clear codes, as if the computer was not properly grounding that wire. Any help or leads are appreciated, this has been going on a long time and I'd love to drive my car again this season. Thanks.

 

joel5.0

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May 16, 2008

#5

• May 16, 2008

• #5

Black Sun 5.0 said:

What exactly is the NSS? Anyway, I spoke to my mechanic again, and what was specifically said was that if the sigal return wire was not manually grounded, they could not get data, read, or clear codes, as if the computer was not properly grounding that wire. Any help or leads are appreciated, this has been going on a long time and I'd love to drive my car again this season. Thanks.

Click to expand...

From that little piece of information, looks like the SIGRTN circuit PWB line in the ECM is open/fried...... or something like.....



Which can be fixed as shown below....... BTSTDTRT plenty of times.

 

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Black Sun 5.0

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#6

• May 16, 2008

• #6

LOL! Where is this part located? Damn.

 

joel5.0

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#7

• May 16, 2008

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It's the computer PWB or board, the EEC is located behind the passenger side kick panel...

 

Black Sun 5.0

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#8

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• #8

FYI: The computer has been replaced twice for troubleshooting.

 

joel5.0

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#9

• May 16, 2008

• #9

Black Sun 5.0 said:

FYI: The computer has been replaced twice for troubleshooting.

Click to expand...

If a VMI check confirms the damage on the PWB, he needs to ID what is causing that circuit to blow + check the integrity of the SIGRTN wire + make sure there isn't a short to power causing the SIGRTN circuit to be damaged. If the root cause of the problem is not corrected, the SIGRTN will be damaged regardless of how many ECM's are installed.

 

Black Sun 5.0

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#10

• May 16, 2008

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I was afraid you were going to say that. If that's the case, where do we start looking?

 

joel5.0

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May 16, 2008

#11

• May 16, 2008

• #11

ECM disconnected, turn IGN ON, check for voltage at the SIGRTN terminal of the TPS connector, TPS disconnected....... or pin 46 at the ECM connector. LUK

 

Black Sun 5.0

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#12

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• #12

You da' man. I'm sending this all to the shop.

 

stykthyn

I want to measure mine. It doesn't look that tall.

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#13

• May 16, 2008

• #13

I am curious how this turns out. let us know

 

allballsmustang

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May 16, 2008

#14

• May 16, 2008

• #14

sounds like stangnet is more help than your mechanic, thats scary...

 

93 LX

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#15

• May 16, 2008

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Stangnet is always more help. Most shops just fix the easy but they dont drive them or care for Stang.. Stangnet people love the Mustang... we know how they work cuz we work on them....

 

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Black Sun 5.0

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#16

• Jun 2, 2008

• #16

OK, here's an update for all the curious folks out there: The problem with my computer has been resolved. Apparently there was a bad splice located somewhere in the harness. I guess the fella who helped me rebuild the car zigged where he should zagged. Either way, the car should be on the road this week. Next up: 5-lug, 4-wheel disc upgrade.

 

Noobz347

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Aug 12, 2015

#17

• Aug 12, 2015

• #17

I thought I would drag this to the top today. It seems like hack-job wiring comes up pretty often. hehe

 

jrichker

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#18

• Aug 12, 2015

• #18

There are 2 primary causes for this problem:
1.) people try to dump the codes and use the brown connector (12 volts for the under hood light) instead of the gray STI connector. Both have the same shape and are located in close proximity to each other. My how to dump the codes notes the differences and dangers of the two similar looking connectors.

2.) Wrong O2 sensor harness; use an Auto Transmission O2 sensor harness with an A9L 5 speed computer and it will burn the trace off the computer PCB as shown. I have an "O2 Sensor harness interchange and modification" tech note that explains the differences and cautions about O2 sensor harness interchange.

 

D

DuderMcMerican

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Mar 11, 2016

#19

• Mar 11, 2016

• #19

joel5.0 said:

From that little piece of information, looks like the SIGRTN circuit PWB line in the ECM is open/fried...... or something like.....



Which can be fixed as shown below....... BTSTDTRT plenty of times.

Click to expand...

What gauge wire did you use to jumper that EEC connection?

 

jrichker

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#20

• Mar 11, 2016

• #20

DuderMcMerican said:

What gauge wire did you use to jumper that EEC connection?

Click to expand...

Use 24-30 gauge wire. Use a little thick super glue to hold the jumper wire in place once it is soldered to the damaged traces. Use some thin super glue to stick the peeled up traces back on the PC board.