devestator_x

iTrader: (1)

So, I tried searching, but any search for "Check Engine Light" comes up with all sorts of threads containing the words engine, check, and light, in any old order.

Anyhow, the other day I was curious if my car had stored any codes and thought about my morning start up routine and realized, my check engine light never comes on before I start the car. I've only had the car since December so I am still figuring out all it's little quirks.

I used a paper clip to jump A and B on the diagnostic plug and turned the key to run. Nothing. No blinking light at all. In fact the only light that comes on is the Choke (which should when the car isnt running with key in run position)

Now here's the thing... do you suspect the bulb is just burnt out? Completely removed? The car runs fine, gets 20mpg and has been nearly flawless. It does have a small bog off the line during the 1st 15 minutes of operation if you punch it (which I suspect is a problem during closed loop) Once it swaps over to open loop, it runs like a champ. This was the main reason I wanted to try to pull codes from it.

Im really hoping it's just a minor issue with the bulb and not something completly jimmy rigged. Under the hood is virtually untouched. It still has the factory CC Carb and none of the wires look hacked at all. The only thing thats been cut off is the A.I.R. system. If the entire computer had been ripped out, Im sure the car would run like complete crap...
Of course my 82 T/A originally had crossfire injection and someone ripped that off for a 2bbl carb, but never swapped the distributor... people swore that car shouldnt run right, but it did with no issues what so ever.

RBob

iTrader: (1)

The CEL bulb could be missing. Common back in the day when it was always on.

The CCC cars also had a lamp driver for it. Not sure how reliable they are. It is another possibility.

RBob.

devestator_x

iTrader: (1)

Ok, yanked out the gauge cluster today and swapped the choke bulb with the CEL bulb. Still no CEL in run position while not running. I hope my ECM isnt fried or anything.

RBob

iTrader: (1)

OK, dug up some info on how the CEL is wired. Hopefully this is correct (appears to be).

Do a key-on, engine-off. Ground terminal D in the ALDL connector. The CEL should turn on. If so then the bulb is OK along with the +12 volts to it. This test just grounds the low side of the CEL bulb.

Check the gauges fuse, it powers the lamp driver.

Unplug the ECM then key-on, engine-off, the CEL should light up. If it does then either the ECM is bad, or it is not getting power.

If it doesn't light up then the lamp driver module is bad.

Note that there could also be an open wire somewhere, and not a bad bulb, driver module or such.

There are two power feeds to the ECM: battery +, (orange wire) and IGN+ (pink/black). The battery feed is via a fusable link, the IGN+ feed is via a 15 A fuse (labeled ECS ?).

RBob.

devestator_x

iTrader: (1)

Thanks for all the usefull info Rbob. I actually got it fixed today. Come to find out, my battery had needed replacing (only 400 cca insyead of 720 cca) Replaced the battery and the Check Engine light functions normally now. Jumped a and B and no codes stored, so Im happy about that. What Im miffed at is not replacing that battery sooner. All the work pulling the gauges yesterday for nothing. I think worst of all in the middle of messing with the gauges, I snapped half the speedo needle off. Luckily it's the older dual needle style and only the Kph side is the one that snapped.

kingbowl93

Thanks RBOB this post helped me diagnose my issue I was having with my SES . Turns out my light driver module was completely missing. I misdiagnosed the symptoms as a bad ECM and Prom at first.

RBob

iTrader: (1)

That's great, welcome to TGO.

RBob.