keeslinger31

My car is throwing code 43. Replaced knock sensor, esc and i have a 7747 computer. I have no idea what to do... i researched code 43 but noone ever says they fixed the problem. thanks in advance

RBob

iTrader: (1)

Code 43 on the '7747/'8746 ECMs has two causes:

Failure of the forced knock test

Run-away knock counts

If the SES illuminates during heavy throttle then it is the forced knock test failing.

If the SES lights shortly after starting the engine it is the run-away knock failing.

Try a search here on the TBI board with my name in the author box and "forced OR knock" for search words. That should bring up several posts on the topic.

If not post back and we'll go from there.

RBob.

keeslinger31

Its definently the forced knock test failing but im not sure how to fix it from reading your posts lots of helpfull hints but i dont want to start throwing money at a problem that could be as simple as a overtightened knock sensor. I wish It would fix itself.

RBob

iTrader: (1)

If it is the forced knock test failing, then over tightening the knock sensor would not cause it. This failure would occur if the engine would not show knock.

For the forced knock test to pass the ECM needs to see that the engine knocked (detonated). Even something as simple as using a fuel with too high an octane rating will cause a code 43.

RBob.

keeslinger31

I am running 89 octane. What should i do...
timing is set at 4 advanced

RBob

iTrader: (1)

You need to figure out whether it is knocking and it is not being reported. Or that it isn't knocking with nothing to report.

The forced knock test has the ECM advancing the timing to force the engine to detonate.

Can you hear the engine detonate during this test? If not then need to try 87 octane fuel and then hopefully it will detonate.

If you can hear it detonate then you need to troubleshoot the ESC system to see why the knock isn't being reported.

Can always cheat and place a push button switch on the ESC signal to the ECM. Wire the other PB terminal to ground. Then after the engine warms up a bit push the button a few times. That should be enough to fool the ECM into thinking that the ESC system is OK.

RBob.

alvanwie

RBob,

I had this also. Finally, decided to patch the code to disable the force knock test. Is there a down side to doing this other than no test of the knock sensor? Seemed like it went into limp home mode when the test failed and then would hardly run.

RBob

iTrader: (1)

When the forced knock test fails the ECM automatically pulls about 8 degrees of timing. It continues to pull the timing until key-off, then key-on again. Note that the amount of timing pulled is a calibration parameter.

Bad for mileage, bad for power, bad for the exhaust (runs real hot). PE and highway SA is also locked out with a code 43 set.

And, until the forced knock test is successfully run, no PE SA or highway SA is allowed.

The patch is the best way to go. The ECM thinks that the test has been successfully run, so it won't run the test again. And, PE and highway SA is allowed.

The patch is even more important with a modified engine. What good can adding 10 to 20 degrees of timing be on a performance engine. Just to force it to knock.

RBob.

Dmity Kiev

Rbob , O have the same problem my timing advance only 8 at all rpm , but i never seen 43 code. I replace all ingnition system components tree times , i put them from near worked car and almays got same problem NO TIMING ADVANCE , I replace ECM to stock L03 with stock bin and still have no advance. I even made new wire harness for ingnition system nothing helps. my ECMs is 6965 now i can patch it for knock test ? Im tired from this 2 month every day works with car ... can somebody help me ?

keeslinger31

I dont really want to patch the ecu. there has to be another way to make it sense knock and without jerry rigging a push button it should just knock