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Code 43 problem...

Discussion in 'The Garage' started by Eagle Driver, Feb 5, 2006.

  1. Eagle Driver

    Eagle Driver Registered Member

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    Well, after two days in the shop and some $600 later (new computer and distributor) I get my K5 back. Driven it for about 50 miles since, and she missed again. Check the codes and it's throwing 43? I read that that is the knock sensor not getting the right signal to the esc...am i right? And what's the fix...cheap and easy will make me feel good right now...

    Thanks fellas
     
  2. Eagle Driver

    Eagle Driver Registered Member

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    by the way, it's an 87 350 tbi
     
  3. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    IIRC, there are several possiblities, all of which are the knock sensor circuit

    I'm sure some one will post a diag procedure, but here are some possible causes

    knock sensor, knock sensor wiring, ESC module, ESC module wiring, ECM, ECM wiring, PROM

    I have seen all of these
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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  5. BigCountryx

    BigCountryx 1/2 ton status

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    thirdgen must be down, so I'll ask some more q's. I've got the same Code 43 going on, mine comes on when I "lug" the motor a little, or when getting into it pretty good and the tranny shifts gears. I just had the 350 swapped in my 1990 and I'm wondering what the TV cable does exactly. Could it be possible that the shop needs to adjust it so that the tranny shifts at a higher rpm? I don't even know if that is possible, but just a thought. If not, why would my ecm throw the Code 43 only in these situations? My Knock sensor is reading, because it counts every time the block is tapped. If the engine is really knocking, what code would it throw?
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    This explains the 43 code a bit:

    http://www.gnttype.org/maint/malf.html#43

    You won't get a code from knock, as mentioned in the writeup, it just retards the timing. Some knock is pretty normal, and you'll never notice it in performance.

    Lugging the motor and a trans shift are both times that knock is likely to occur. Figuring out why the code is present on the other hand...

    Only other chart I've got is this:

    http://www.chevythunder.com/esc_map_code_43.htm which is 90-92 TPI, but it is likely almost identical, except I don't believe your knock sensor stuff is part of the ECM.
     
  7. BigCountryx

    BigCountryx 1/2 ton status

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    Thanks for the links, and the advice. I will try followin the flow chart this weekend.

    I was rereading the statement above and wondering. The code is intermittent, but repeatable. As in, I can reproduce it by speed/throttle manipulation, it doesn't seem to be a wiring problem to me. The knock sensor "counts" like it's supposed to when hooked to the scan tool. So, when you say a knock won't throw a code, only retard the timing, will the timing being retarded throw the code?

    I haven't checked the voltage signal yet, and I will, but could could a knock sensor read bad, as in, too sensitive, due to high or low voltage? Being it was an engine swap, something like the knock sensor wire being too close the the plug wires, causing a higher than normal voltage (like the Flow chart says) seems plausable.

    Sorry for all of the questions, just trying to get a gameplan together before attacking this problem. Thanks.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    One of the things I've never seen mentioned is how much knock (or how often) is acceptable in "normal" applications, if any. GM obviously didn't run them on the ragged edge of destruction.

    My TPI setup knocks occassionally, but never throws a code for it. I know my timing and fueling are off because of the modifications I've done, which is going to lead to problems like that.

    Knock sensors can go bad, and I suspect that if the computer is CONSTANTLY reading knock, or retarding timing, the code is probably set.

    Have you watched the knock counts while driving as well, (especially when the code is set) or has your monitoring with the scanner been only in park or neutral?
     
  9. BigCountryx

    BigCountryx 1/2 ton status

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    I've only monitored knock counts while idling in park. The code goes away and everytime I kill the engine, it has even gone away after driving a while before. I can avoid getting the code by putting everywhere and being aware of rpm (not to lug it at all). As soon as I get into in too high a gear I get the light. Sometimes just driving a little too hard during 1-2 shift it will throw. I also find that I am getting a bit of an unburnt gas smell when running.
     
  10. BigCountryx

    BigCountryx 1/2 ton status

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    Still haven't found anything out of the ordinary, except that when checking my idle, I unpluged the idle wire under the dash and nothing changed. Shouldn't the engine idle down and obviously bog a little? Also I have to advance the timing to get the thing to run. The engine dies when set at 0* like the manual says. Could these be signs that are pointing to something I'm not seeing. Makes me wonder about my ESC.
     
  11. txfiremank5

    txfiremank5 1/2 ton status

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    I'm pretty sure mine threw a 43 once. I went to check the knock sensor and it turned out the wire going into it had a damaged connection. I spliced in a new one it was good after that. After that someone mentioned it was more often that the cennections get bad, vs the sensor.

    Anyway, that's a pretty cheap check, or replacement, .. good luck.
     

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