code 42... Electronic Spark Timing (EST)

'88 s10 blazer 4.3L

keep getting a service engine light off and on with this code 42... and after reading about it i think i understand it is something to do with something becoming grounded or open, or that some wire connections are bad, or that the PROM isn't seated correctly in the ECM... truck runs like crap when the light is on.

Any suggestions on where to start or better yet, how to fix it? just replaced plugs, wires, distr. cap, and ignition module about 4 months ago.

there is a one wire connector by distributor. that connector allows you to set basic timing when you replace parts that effect timing such as distributor cap and rotor, ignition module, etc. your base timing is off or you forgot to reconnect this connector. you will need to disconnect this connector and set basic timing. get a timing light and set basic timing. after you set basic timing, turn engine off reconnect the connector and start engine again. when this connector is disconnected it tells the computer not to advance the timing so you can set basic timing. if you dont set basic timing well you will have the problem you are having or if the connector is disconnected the timing will not advance as the engine revs and you will have no power. i believe both of these concerns will trigger the check engine light.

i had this same problem on an 88 2.5 one time. the culprut on mine was a bad wire on the pickup coil in the distributor. it some how got pinched and was grounding out on the body of the distributor. good luck

Fought this for two months with my 93. First have engine idling, reach down behind distributor and wiggle the four wire connector that plugs in the ignition module. If the engine stumbles, there's the problem. If not take out the module and have it tested at Autozone or other place, they have a test for the ESC. I finally wound up cutting the plastic enclosure off my module and soldering the four wires directly to the module. Had a real battle with this deal, replaced computer, module, knock sensor, jumped wires, nothing worked until I finally found the bad connector.

cool.. thanks everyone.. i'll try and test out that stuff tomorrow and see what happens.

One more quick question.. even if the Check engine light isn't on, would any of the above problems cause the truck to run kinda crappy? When the light isn't on, the truck still idles rougher then normal when i have it in D or R.

Thanks again

Code 42 is a bad ground coming from the electronic spark control.

Check its ground.

in my Haynes manual and in a search i did on this board,... code 43 is for the ESC... 42 is the EST... or is that the same/related?

Code 42
Electronic Spark Timing
Circuit Condition - Open or Short to Ground

Check your computer grounds and your engine grounds.

alright.. i'll search around.. dunno what im really looking for though :-(

grab a chilton's repair manual bro.

Right now you are blind.

u got that right man.. i'll see what i come up with tomorrow when i play around with it..

My husband has a K-5 Blazer. His ran like crap when it did run, and finally would no longer get spark. He put over $400 into it, replacing everything from the distributor cap to the electronic ignition. Hr had three mechabic friends walk away scratching their heads. He had power going to the distributor, but no spark.
It was not until my husband took his alternator (brand new) in to be checked that the technician there asked him if he had the California Emissions issue distributor assembly. When my husband said yes, the man told him that for a few years they installed a module located on the firewall, and that module controls the spark.He also said they no longer manufacture them. My husband was instructed to cut the module off of the firewall and splice the wires together, which he did, and now it runs fine.
If that is not the problem, it might still come in handy down the road to have this tidbit of trivia.God Bless