1995 CHEVY 350 TIMING FOR 1500 SERIES - 1995 Chevrolet C1500

SOURCE: How do you set the timing on a 350 chevy engine in

If the distributor hasn't been taken out, the timing can be set manually but you have to disconnect the distributor wire behind the glove box inside the cab. Tan wire with white tracer it is taped up to the a multi wire harness but is the only one with a single plug. Disconect the plug and use your timing light on the timing mark to set timing per specs. Rotate the distributor as needed to advance or retartd as required for the correct setting. tighten the dizzy clamp and plug the tan wire back together. The computer will now be fooled asd to what the base timing is and advance from there.
Contrary to popular belief, 96' and up do not have this wire. Timing has to be done with a programmable scanner.
Dan
Hope this helps.

SOURCE: Error 42 electronic timing on a1991 chevy truck

I've seen this problem a few times pull the distributor and inspect the gear on the end, the teeth on the gear will get sharp like a knife and this causes to much variasion in the timing for the computer and it sets this code. replace gear the gear runs around 50 bucks.

SOURCE: I am having trouble setting the timing on a

The wire is either at the firewall under the black cover with the three plactic nuts. Or its under the passenger carpet all the way above the passenger feet. Or its right in the corner between glove box and door. If its never been touched it should be wraped and held in place with tape.

The wire is brown. Also if you want to bypass that what we do is goose the engine. For a split second the timing will drop to 0 if you do a quick 1500 rpm goose.
At idle with the wire hooked up about 16 to 18 degrees is normal. As soon as you unhook the wire it should drop to 0

SOURCE: 1995 chevy p/u with 4.3 engine 1500 series.

code 12 is always present in gm motor products. it simply means no tach signal because engine is not running. i would go with the simple first and clean the throttle body real good . that takes care of 99% of idle problems.

SOURCE: I have a 1992 Chevy pick up 1500 series. 350

there is no adjusting you can change the throttle position sensor this tells the ecm what the idle is also check for vacumm leaks and the pcv