How do I get codes from computer in 87 Pickup?

Changed from 305 to 350 with TBI. Does not idle good and gets "check engine" light now. Changed O2 sensor, Knock sensor, EGR valve and solenoid but still same symptoms. Any suggestions? Also, is their a way to put the computer in diagnostics mode to tell why the check engine light is on and if so, what do the codes mean. The check engine goes off for a while if you turn the ignition off and back on.

I dont know if a camaro and a truck computer are the same, but I had the same problem with my friend's '88 TBI camaro. We pulled the 305 and replaced it with a 350, and it wouldn't idle right. To get the codes from the computer, I had to pull of a panel below the steering wheel and connect 2 pins on a connector, and then turn the ignition on. It flashed code 12 first, which meant the computer recognized I was trying to get codes, and then it flashed the other codes 3 times. It told me the O2 sensor was reading lean. Unfortunetely, I dont have the equipment to fix the problem, so I had to take it to a service shop and let them do it.
If you have a chiltons manual it should tell you how to do it.

I dont know if a camaro and a truck computer are the same, but I had the same problem with my friend's '88 TBI camaro. We pulled the 305 and replaced it with a 350, and it wouldn't idle right. To get the codes from the computer, I had to pull of a panel below the steering wheel and connect 2 pins on a connector, and then turn the ignition on. It flashed code 12 first, which meant the computer recognized I was trying to get codes, and then it flashed the other codes 3 times. It told me the O2 sensor was reading lean. Unfortunetely, I dont have the equipment to fix the problem, so I had to take it to a service shop and let them do it.
If you have a chiltons manual it should tell you how to do it.


To read the trouble codes on your 87 Chevy, look for the ECM black box under dash near gas pedal. The ECM may have a short lead with connector for the Assembly LIne
The box will have 2 holes in the upper part of the box or locate the assembly Line Diagnostic Lead which may have a cover on it.
A terminal is system ground-- B terminal is the test terminal.
On terminals A and B of the connector or black box- insert a paper clip.
Turn Ignition to "on" position but DO NOT start engine.
Now watch your check Engine Light start flashing.
The first code will be Code 12 and flash like this- flash, pause, flash, flash, pause then it repeats three times. Code 12 means the engine is not running. the cooling fans will come on as well. this is normal.
Mark down the next code-if any and that will be the culprit that set the code. Example- 3 blinks pause and 6 blinks is code 36- O2 sensor below normal. If the 2nd code after code 12 is another code 12-- nothing is wrong.

Go to autozone and get yourself a manual it will give you all the info you need. Just curious did you upgrade the ecm and injectors along with the engine

www.troublecodes.net/gm

explains it all there, and shows you illistrations.