Alright,

So when I installed my newly rebuilt carb last week, my check engine light instantly came on. Now, since the car is running rich, I wasn't too worried about it however, since I'm having some fairly serious part throttle issues, I figured I'd pull the codes just to see if anything else is being thrown. Performed the paperclip read and...nothing. Not even the "12". Light stays solid. Car is an 84 T/A with a modified 350 and CC Qjet. To pull codes I should short pins 6 and 12 if I'm reading it right. One thing I did notice is that on the OBD connector, is that there are no bottom row pins. I can't say they were there before but there aren't any now and there are no wires with pins on them anywhere near it that I can see. So you all don't think I'm nuts, I have pulled codes on this before with this engine and I haven't done any work to the car's electrical in that area so I'll have to make 2 assumptions here.

1. That the bottom pins weren't there before
2. The ECM isn't responding.

Does anyone have any input to this? Any help would be great.

 

 

Are there two bulbs in the check engine light? I was under the impression they only had one each in the warning lights. Where are the connections you're talking about so I have an idea where to start digging? Obviously, at the ECM, but where else? Thanks!

 

 

I'm having the same problem. I put it in KOEO, and the computer doesn't throw any codes, not even "12," or even turn on, which you can always hear it do when you put the GM test key in.

As with yours, mine also has no bottom row of pins. There's just a top row, and there's one missing. See illustration below

- _ - - - - -

Have you figured out why it isn't flashing yet? I'm having the same problem and I think I may have a bad computer. Also, my MPG has gone from 15 city 23 highway to 11 city 14 highway, and I was told a bad ECM could keep the metering rods wide open.

Man if you could let me know what you found out it would sure help out a lot. Thanks

 

This turned out to be a burned out ECM fuse. Apparently when I pulled the 4-wire flat connector while checking my base timing it blew that fuse. The fuse is a 10 amp red fuse on the top of the fuse box. As you sit in the car, it's the one closest to you on the right (upper corner).

Without your ECM controlling the MCS, the car goes into a "LIMP" mode where it goes super rich so the car can be driven though it won't run well at all which causes poor power and gas mileage. Hope this helps!

 

Unless GM did something different on yours, every OBDI GM Ive ever seen went into diag mode when pins A&B were jumped. A & B are in the top row, far right.

 

Yes, I forgot to add that you use the top two on the right to pull the codes. I used a paperclip to jumper those two. It'll do a "Flash....flash flash, Flash...flash flash. that's a 12. 1, then 2 in fairly fast succession. It'll throw each code 3 times before moving on to any others. 12 is "normal" and means the diagnostic system is working correctly. The first "fault code" will immediately follow the third "12".

 

If your ECM isnt going into diag mode with A&B jumpered, check A for continuity to ground. Try grounding B by a test lead to a known good ground. Sometimes the ECM can be finicky. Be sure to install the jumper, then turn the key on.

 

The fuse under the dash is for 'engine controls'. It provides power to all of the stuff the ECM talks to and will trip when one of the engine management leads, like EGR, MCS, etc. is grounded. The actual power lead to the ECM runs directly from the battery along the fenderwell alongside the fuel lines. Single wire connector and a fusible link. Either one open will cause the diagnostic lamp to fail.

 

This turned out to be the fuse being blown under the dash. Must have happpened when i pulld the flat 4-wire connector to set the timing.

 

Similar event happened to me..The fuse was blown, and was causing the SES light to go on..During the the two weeks the SES light was on, the clicking from the MCS had stopped during starts. I noticed a bit lower performance and a slight hesitation at take off from 5-10 mph if I eased on the throttle.

I changed the fuse and now the SES is off. However, the car dies after 10=15 seconds of running time..Dont know what to do next to fix this problem.. And I need to get it SMOGGED by end of the month.. Any suggestions.?.

 

plz help
hey i was wondering if u cud help, my ses light goes goes crazy whilst during a normal start up AND when connecting A and B in ALDL port and as lights flickering (as tho theres a bad wire)the engine drops revs, does this mean its ecm problem or electrical, my car 86 iroc TPI 5.0 has been 'broke' for 1 WHOLE YEAR NOW and its killin me im over in scotland and no want wants to work on her plz help heres a vid
p.s ive changes plugs, leads, 02 sensor, coolant temp sensor and thermostat, new battery.car ran perfect till it was out for a hard drive (which wasnt common) my gut feeling is its electrical i cant get any codes

this second vid is with the A AND B bridged, it wont read a code
http://www.youtube.com/watch?v=InNYu...3&feature=plcp