1990 Chevy 1500 keeps flashing OBD1 code 43

Discussion in 'Chevy Truck Talk & GM News' started by sportking159, Jul 4, 2012.

  1. sportking159

    sportking159 New Member

    I have replaced the knock sensor and the Electronic Spark Control Module. OBD 1 code 43 continues to flash even after i reset the ECM. Also the engine lacks power, especially when climbing hills. I Have checked the continuity of the Blk/blue wire that runs from the knock sensor up to the ESC Module. Continuity test was good. Then I back probed the knock sensor cranked the engine and tested for voltage. I found there was no voltage. Please respond if you can help me. Thanks
  2. GMfanatic

    GMfanatic New Member

    Have you checked timing? For your truck (going off of my 1995, should be close to the same) there is a brown or brown w/black stripe wire with a connector located either under the dash on the passenger side by the blower box or in the passenger side upper firewall. This is the electronic timing control wire. It varies timing on the fly using the computer. You should check your timing, if you havent already done so using this method.

    1. run truck until it reaches operating temp.
    2. turn truck off
    3. disconnect the electronic timing control wire, the check engine light should come on and idle RPM should raise slightly
    4. set timing, stock settings from the factory is 0 degrees, you can run up to 5 degrees advance on pump gas but it is not recommended. I set mine to about 2-3 degrees advanced, it makes the truck run a little better and get a little bit better MPG
    5. shut off the engine and reconnect the brown or brown w/ black wire
    6. start the truck back up and drive it for a couple of miles.

    I would do this and probably run about half a tank of premium through the engine just so you're absolutely certain that it is a malfunction in the electronics and you don't actually have a knock that you may not be able to hear.

    The higher octane fuel will help your engine ignite the fuel more efficiently, meaning if the timing is off (advance or retard) it will burn it all off either way. Assuming the timing is not totally out of wack, the higher octane fuel should do away with any timing related knocking.

    Hope this helps!

    If you come up with anything else or need any specs feel free to pm me. I work as a parts guy at a chevy dealer and have access to all of those sorts of things. Manuals, TSB, ect. Also I run their parts website if you need any parts for your truck give me a holler.
  3. Premeir620

    Premeir620 New Member

    I was going crazy with my 1992 GMC 1500 and the infamous code 43. After nearly 3 days diagnosis it ended up being a knock sensor open. New sensor was 3.9K ohms.
    RayVoy likes this.

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