so i am trying to read the codes from my 87 iroc 305 tpi auto

when the car is running the light is always on, when i shut the car off and plug in the code reader i just bought then turn the key to `on` the light will not come on or begin flashing any codes. if i unplug the code reader and turn the key back to `on` the light still won`t come. the light should come on to verify that the light works before starting the motor(from what i have read), and all my books say to plug in the decoder with the key in `off`then turn the key to `on` but not to start the motor and the ses light should flash 12 to confirm the system check. am i doing it right or missing something or what is going on? any help would be appreciated

mike

 

Sounds like the ECM is bad, or there are ground issues. Since the light does work this is what it should do:

At key-on, engine-off, the SES should turn on, blink off, then turn on solid. Can repeat the test after at least ten seconds of key-off.

Since the light is only on while the engine is running, the ECM isn't properly controlling it. Which takes us back to my opening sentence. Be sure to check the grounds at the rear of the passenger head.

RBob.

 

THANKS, I ALSO NOTICED MY BATTERY WAS DEAD 2 DAYS IN A ROW (AFTER CHARGING) AND WHEN I POPPED THE HOOD TO LOOK AROUND AND HOOK UP THE CHARGER I WIGGLED THE WIRES BY THE BATTERY THAT COME UP TO A RELAY OR FUSE BLOCK RIGHT BESIDE THE RAD. WHEN I MOVED THEM THE FAN TURNED ON AND CAR HAD NOT BEEN RUNNING AT ALL SO IT WASN'T HOT, AND THE KEY WASN'T ON EITHER. IT LOOKED A LITTLE CHARDED LIKE IT HAS SHORTED OUT SO I WILL NEED TO REPLACE IT REGARDLESS SO I NEED TO KNOW WHAT IT IS. IF YOU COULD HELP THAT WOULD BE GREAT AND WOULD SAVE ME ALOT OF TIME GOING THROUGH ALL MY BOOKS

 

Sounds like it is the fan relay. Although I don't know the '87s well enough to know for sure. But since you wiggled those wires and the fan ran...

May also explain the dead battery, as the fan may be turning on in the middle of the night.

RBob.

 

THATS WHAT I WAS THINKING, I'LL GO THRUE MY BOOKS TONIGHT AND SEE WHAT I CAN COME UP WITH

 

so i replaced the relay tonight so i`ll see if the battery is dead tomorrow night to see if that was the issue or not. sometimes when i turn the key on but not start the fan turn on (almost always) this is not supossed to happen is it? i thought it only turned on when it was at temp. maybe another issue due to a bad ecm?

ok, so i pulled out my ecm to check the grounds but all i found was the 2 main harnesses. i tried to check the ground at the back of the pass side head and it looks good at the firewall but there is no way to look down in behind the motor to check that bolt, it is attached still, as i pulled slightly to see if it had broke off. i also checked my fuse panel for any blown fuses but all were good. does anyone know if there are other grounds to check or any fuseable links to check that are to protect the ecm? i just want to cover all the bases before ordering the new ecm as they are exchange only and no refund

 

so it wasn`t the fan relay that was draining the battery....it is dead again, so i now i have to look around for the next idea

 

Can you verify an amp draw with key off by hooking up a V meter? Validate a draw and then start pulling fuses.

 

i can but can you tell me step by step including how to set up my volt meter to do that , i have never done anything like that before. i won't be able to try it until sunday, but i will definatly try that, i just need it figured out so i can order my new computer already, i don't want to put in a new computer incase it shorts it out and fries it too
thanks, mike

 

I am no expert by any means on electronics. Others here may explain further.

Set VMeter to ohms. all cars have some draw engine off so you will see draw. Question is if draw is more than it should be. Shop manual may illustrate expected normal draw. Regardless you will see draw. With meter attached have someone or yourself pull a fuse and witness new draw. Replace fuse. Continue on other fuses. One fuse may show a signifificant decrease in daw. That is the circuit that is drawing down battery.

I think rear hatch and power seats may be two ploblem areas. Also under hood lights.

 

thanks, i`ll try that when i get home this week-end