cant seem to get the ecm to read me any trouble codes,checked bulb in the dash its good but i get no codes no c12 computer access its like its not even there,im using a parts store key to jump a and b also tried a piece of wire still no responce from the computer (HELP PLEASE).

You're saying that when you jump the A/B, the dash light doesn't even flash? Or that you get no ALDL data stream?

Are you sure you're jumping the right pins? Just jam a wire in there, and make sure they're the right pins....

When you turn the key to the on position without starting, does the Check engine light come on? how about the fuel pump? does that run for two seconds?

If the bulb is good, but you get no SES light when jumping the diagnostic terminals and turn the key ON, that suggests the ECM is bad or is not getting power.

[This message has been edited by Formula88 (edited 11-28-2004).]

hey guys im sure im jumping a and b terminals,but the check engine light does not come on.also the car will crank turn over then die,is it true that on 85s only another 85 ecm will work?it a 2.8 by the way and it has the rn hyper tech chip in place of the stock prom chip. thanks manny

Sounds to me like you're not getting power to the ECM. Got a test light? Check for power at the ECM connector terminals B1 and C16, both have orange wires and both should have power full time regardless of key position.

Here's the schematic from the '86 service manual:

Also, check for power at A6 when the ignition switch is in RUN. If you don't have full time power at B1 and C16 then check for a blow fusible link or damaged connector at the terminal block by C500.

If you don't have switched power you'll need to do more checking in the ignition switch area.

JazzMan

quote Originally posted by the wraith: 1 the check engine light does not come on. 2 also the car will crank turn over then die 3 is it true that on 85s only another 85 ecm will work?

1 - check what jazzman has said about power
2 - that's the <400rpm where it doesn't use the ECM
3 - You can use any year ECM, just find one that came from the same or similar config (ie, 14" tires, standard).

An '85 PROM will not work with an 86/7/8 ECM.

Yeah, JazzMan has the ticket. Either the ECM is bad or the ECM isn't getting power. I had that same problem on my Formula and it was a broken wire in Circuit 240.

Check for 12V at those 2 orange wires going to the ECM. If you don't have power there, the ECM isn't coming on.
On my car, as a limp home repair, I ran a line from the cigarette lighter to the 2 orange wires going into the ECM. The cigarette lighter wire is on another circuit, but it's also orange and is hot all the time, and just happens to be close to the ECM so you only need a foot or two of wire.

That repair worked for several months, until I finally found the broken wire in the bowles of my wiring harness.

thanks guys based on what was said i think my ecm is bad,if you jump a and b with the key on then hook a test light to the brown wire on the harness below the two bottom ecm plug ins, the test light will act as the check engine light, it will blink of what ever codes you have.my test light just stays on no blink! this means my ecm has power but is bad.i think? thanks manny

After checking out the schematic.........Jazz Man has got to be right. Good luck and peace.

Phil

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I am always available to help those that need help. Since my back injury, I cannot work on many of the aspects of the cars, but I can offer the knowledge of my 27 years as a GM technician. Bring the questions on................!

hey guys i jumped a hot wire from the lighter, to the two orange wires on the ecm and it came on so my ecm is not getting power the car cranked and started with the jumper,so this means i have a short or somethin, the ecm ing fuse is not blown and the fusable links by the battery are all still good, where to next? thanks manny

Gotta be the fusible link or the wiring from there to the ECM. The two orange wires get power directly from the fusible link, they don't go through any fuses or other circuits.

Remove the connectors from the terminal block by the C500 connector and clean any corrosion off . See if the ring terminals are still firmly attached to the wires. Use a sharp probe and test light to check for power on both sides of all the fusible links.

JazzMan

where is the c 500 connector?

quote Originally posted by the wraith: where is the c 500 connector?

That's the big ass connector right by the battery. Held down by a 1/4" bolt.

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87/88 V6 5spd "FormulaGT" Turbo
85 Bright red GT 4spd (with matching 1:18 diecast and 1:24 plastic models!)
86 SE (custom body in progress)

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http://www.fieroclub.com
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thanks forgive my ignorance i didnt know what it was called, you guys are awesome. thanks again manny

Here's a pic, the C-500 has been disconnected. You can see the terminal block just below it, in this picture the fusible links are loose:

C-500 is between the battery and the strut.

JazzMan