Captain Nguyen

I have read about knowing the error of service engine light.

I did connect port A + B with wiring.
Then key on "on" and waiting.
No flashing, still light up.

Would it help with ALDL Diagnose?
Or is it break wiring?
What I see on ALDL connector is, it has 5 wiring.

And can I use this to view error?
ALDL connect serial

And which software can I better use with serial system that I would build.

RBob

iTrader: (1)

If the SES doesn't flash with A & B shorted together the ECM may be bad. At a minimum it should flash code 12 (this is because the engine isn't running).

Try this, remove the A/B short, then after the key has been off for at least 10 seconds. Observe the SES light as the key is switched on (engine off). The SES should come on, blink off, then come on solid.

Can repeat the test after the key has been of for at least 10 seconds.

If the SES does NOT blink off then the ECM is bad or the MEMCAL is missing, or something is wrong. It must do the blink for the ECM to be running from the calibration (PROM/MEMCAL).

RBob.

Captain Nguyen

Yes I tried.

Connect A + B en turn key on. (not running engine)
But SES does still on for long time, no flashing.
I have looked again.

-----------------------
--| F | E | D | C | B | A |--
| |-----------------------| |
--| G | H | J | K | L | M |--
-----------------------

There is 5 wiring at: F, D, C, B, and A.
No E????
This is needed for 160 Baud reading or whatever.
And G, H, J, K, L, M has no wiring.

And I have also creaded ALDL to PC interface (serial)

Nothing work.

So you think ECM would be bad?

Where would ECM be?
Under passanger?
Only what I found is Black box.
Not the ECM what I saw on ebay.
1985 Trans Am 5.0


My car is:
1985 trans am Carb 5.0 V8-305ci.

Captain Nguyen

That black box is for cruise control.
Anyone know where ECM located?

Cflick

That photo is the ECM.

Exactly, step by step, what happens.
Key in ignition. Turn key on, but NOT start. SES light does ????
Turn key off.
Wait ten seconds.
Wire A to B.
Turn key on.
SES light does ????

Captain Nguyen

Key in ignition. Turn key on, but NOT start. SES light does "ON" not flashing.
Turn key off.
Wait ten seconds.
Wire A to B.
Turn key on.
SES light does "ON" no flashing.

Cflick

As Rbob posted, it looks like a bad ECM, loose chip, something is wrong.

Where it is depends on the vehicle. Mine is under the dash above the glove box, but it's also a truck.

Captain Nguyen

I think so that ECM would be bad.
Thnx for info, I'll look to ecm tommorow.

But will this works with my car?
ECM 1226870
Because I read "removed from 2.8L", I have 5.0L.

Captain Nguyen

I have looked today where ECM located.
Friend has '84 firebird and 89 trans am gta.
I saw where ecm located.
And I was looked to my car.
WTF! No ecm!!!
Even a wiring harnes.

That could be?

Cflick

Possible that vintage, but more likely it's just someplace else.
Hard to get an SES light at all with no ECM.

MrBill85T/A

iTrader: (2)

My 85 T/A is a TPI and it is located under the pass side dash right behind the front section or it maybe behind the kick panel

Captain Nguyen

I have also looked behind kickpanel.
Nothing there.

RBob

iTrader: (1)

My car is:
1985 trans am Carb 5.0 V8-305ci.

It is possible that the vehicle was 'de-smogged.' Or, it is an export version that never had an ECM. Note that the CCC vehicles also ran a SES light driver module. It may be that this module is still in place which would turn on the SES light.

Check the carb for an MCS and the distributor for a vacuum can.

RBob.

Turbo Lover

I am having this exact same problem on a 1989 5.0 TPI. Does one of the pins that need to be jumped usually to have power? I want to check this when I get to my shop to make sure it has power. I have checked all the fuses but just want to make sure. When I jump it now the SES just stays on all the time. No blinking to show codes. I had the engine rebuilt but not sure how that could have killed the ecm. It was working before I had it rebuilt because I checked the codes then because it has always run rough.

If you have any more experience with this problem please join in on this thread.

Thanks
craig

tpiselli

iTrader: (1)

Hi folks,
I'm having the same problem with my LU5 1983 Trans AM. What you are seeing is a failure of the "Diagnostic Circuit Check" test. In the 1983 manual it actually has two ways of running and trouble shooting this situation. I don't have my manual here at work with me but I'll give the section in a follow up. Here's how one of the methods is performed (for all steps don't start the car):
- turn ignition on - check engine light should be on.
- turn ignition off and jumper pins A & B.
- turn ignition on again - check engine light should flash 12 three times (I think it's three times, I'm doing this off the top of my head).
- turn ignition off again - disconnect the white ECM wire harness from the ECM.
- turn ignition on again - if the check engine light is out then trace the ground wire for the ECM; I thin it's pin 5 in the white wire harness, a black wire with a white strip.

For the other method after you jumper pins A & B and still have a solid check engine light you have to measure the voltage of terminal C to ground of the lamp drive module. Based on the voltage value you go down two different paths for trouble shooting. Since my wiring harness has been severely hacked I can't find my lamp driver module (the manual says it's taped to the IP harness near the console but I don't see it).
I'd appreciate a picture of one
Hope this helps, I'll try to follow up later this evening.

tpiselli

iTrader: (1)

Just a quick follow up; In the 1983 Firebird Service Manual you can find the Diagnostic Circuit Check in the Emission Control Systems section; page 6E1-36 and in the Electronic fuel & Crossfire Injection section; page 6E2-25. In my earlier post the first method I mentioned was from the Crossfire section and you need to back probe the white ecm connector pin 3 ckt 451 with a test light to ground.