Error 43 on 92 Suburban Electronic Spark Control?

I have a 92 GMC suburban w/ 98k 4x4 automatic I'm getting ready to sell. It's in VERY good shape for the year, only one problem. When I really get into the gas - like floored, or it kicks down to passing gear on a hill, It makes a short noise, like a 1-2 second purr, like If you purse your lips and roll your tongue and breathe out real hard at the same time (lol, I know you get that kind of stuff all the time, but that's the best way to describe it.) And then the Service engine soon light comes on. It clears when you turn it off and back on again. There's no difficulty shifting at any time, before or after the problem. Nothing. Seems to have no effect at all aside from the light.

I ran the diagnostic where you short the A and B sockets and it came up error code 43 = Electronic Spark Control. Some other sites said it may be due to low voltage or something.

Thanks! fuel pump ,
check code if it's multiple code cylinder misfire it's the pump sounds funny,but using super unleaded will set this code.under heavy engine loads the computer will run a self test and advance the timing.if a ping or spark knock is not detected code 43 sets. All rightey, First I'll try unhooking the battery for a minute or so to clear the codes and try again. Thanks for te helps! Disregard this:
Anonymous wrote:fuel pump ,
check code if it's multiple code cylinder misfire it's the pump



Code 43 concerns the electronic spark control circuit of the ignition system. Basically it is a check and control of the ignition timing advance circuit.

If the knock sensor sends a continuous knock signal to the computer or the knock sensor sends no knock signal as the timing is advanced to the point that a knock should occur the computer will set a code 43.

From the noise you described it sounds as if you are getting spark knock on hard acceleration which the computer is unable to control for some reason. When a knock is detected the computer will retard the timing advance until the knock goes away. If the computer reaches a predetermined degree of ignition retard with no decrease in knock the computer will also set a code 43.

Ok enough theory.

Some things to check are basic ignition timing, EGR valve operation, engine temperature (running hot), fuel mixture and basic knock sensor circuit operation. Fuel mixture and knock sensor circuit response can only be checked with a scan tool so you may have to have a professional diagnose the truck if the timing, EGR and engine temperature are not the problem.

I have run across a few 2.8L and 3.1L GM engines that have had faulty MEM/CAL packs (program chips) that will cause this type of problem but as yet have not seen any larger engines with the same problem. I assume we’re talking 5.0L or 5.7L here.

Check the basics I suggested and see a professional if you don’t find the problem.

Good luck My truck, 1988 Chev. 1/2ton 2wd 5.7 does the same thing, but it clears itself. It has never brought the check engine light on. (the light does work, I have gotten VSS codes out of it). Should I worry about it? Should i try higher octane gas? broughy84 wrote:My truck, 1988 Chev. 1/2ton 2wd 5.7 does the same thing, but it clears itself. It has never brought the check engine light on. (the light does work, I have gotten VSS codes out of it). Should I worry about it? Should i try higher octane gas?




Normally if the computer does not set a code 43 the ESC circuit is working properly. If you are getting a spark knock on hard acceleration you should check the basics as far as base ignition timing, EGR operation and engine temperature. An engine that burns excess oil or is running too lean can also spark knock under conditions of heavy load.

If the computer is setting a code 43 and all the basics have been checked you can test the response of the knock sensor if you have access to a scan tool. View the knock display on the scan tool with the engine idling at operating temperature. With a hammer tap lightly on an engine lift bracket or an exhaust manifold. The scan tool should display that a knock is detected. If no knock is detected you will need to follow the test procedure of the knock sensor circuit in your repair manual.

I don’t have my information system on my home computer so I can’t verify this pertains to your truck but most GM computers use the VSS circuit as an indication of engine load. If the VSS circuit is not working it may also contribute to your problem.

As far as this being something you need to worry about it depends on how severe the knock is and how long it lasts. A short 2-5 second knock on hard acceleration most likely will not cause any damage. But a long or sustained knock under light or moderate load can destroy an engine.

If using a higher grade of fuel reduces or eliminates the knock than you may want to consider changing to a higher octane fuel. But remember the reason a higher octane fuel reduces knocking is because it is less volatile than a lower grade fuel. This means a higher octane fuel mixture will be harder to ignite in the combustion chamber and may lead to lower fuel mileage and reduced engine performance especially when cold.

Hope this helps. Yup, it's a 5.7 Thanks for the great help Venturi, that's some good stuff. I'll first try the resetting of the computer and then next time I fuel up I'll use some of that $2 premium - ack! Mine is just a short 2-4 second knock, usually i can count 2 or three knocks. It does burn oil, what older chevy doesn't? Not to bad though. The VSS is fixed. It doesn't do it under what i would call excessive load. About half throttle. and like i said it stops. Thanks for the info. Glad to help both of you. Car Repair Talk's forum.