Peter M

I bought a used 95 Chev 2500 4x4 with a code 12
My code book reads Code 12= "Diagnostic mode; No distributor signal to the ECM; System pass."
The truck idols great in park and neutral but when put in gear(after it warms up) it runs rough. but always good in park and neutral.
When I accelerate fast(step on it) it feels nice but at a slow acceleration the truck vibrates like mad also at a coasting velocity there is a constant shimmy or vibration
can someone tell me in lamens terms what I should be looking for as far as my engin code is telling me.
Im fairly mechanically inclined but not so much with electrical components(relays, sensors ect)
I checked the plaugs wires and distributor all seem well and clean.
And I thought possibly torque converter? did trani flush and filter change to no avail

2wd-K5

how is the cap and rotor? the code 12 u got is normal, there is no signal when the truck is off and throws a code "12"
http://www.extreme-check-engine-ligh...%20Decoder.htm
check it out this explains it better
even if your plugs and wires look good i would change them just to narrow the possiblities as well as the cap and rotor, and while u have the plugs out do a compression test to narrow out more details
hope this helps

Peter M

Thanx 2wd-K5 Ill change the cap, plugs and rotor tomorrow.
Do you have any idea what the compression should read(ill also pick up a manual.)
It has a 350 5.7L throttle body

Peter M

The whole reason I checked the engine code in the first place was the engine light came on while I was on the highway about 50 km out of the city, When we got to our destination the engine light was no longer on after I shut the truck off.
Driving back to the city the engine light came back on again. but after shutting the truck off at home once again the engine light was no longer on. How can I retrieve the code that its registering if it wont stay on after the truck is shut off. I tried to read the code with the truck running but it spewed a 10 or 12 digit code.
Code 12 is all I get once the truck is shut off

2wd-K5

i am not an expert on codes, but if u research it a bit, u can find your answer, compression should be around 150 psi, and no cylinder should drop 20 psi below that