Hey guys - summer's coming and i'm looking forward to ironing out the last bugs of my car. My basic question is this: I know i have the wrong electronic spark module because i switched to a 350 but still have a 305 unit in the car (I did however replace my knock sensor). All last summer whenever i stood on it from a cruise the car threw a code which consistently came up as "esc". I know some of you guys have replaced this part before - where'd you get it and do you have the pn? Thanks in advance!

TRP

Here's where my baby sits at present:

1988 SC Camaro

Tangerine Orange w/White SS Stripes
IROC Hood / Decals
B/M Short-Throw Shifter
WC T-5
3.73's / Limited Slip
355 cid SBC w/TBI
~340hp / 350ft lbs
Holley 670 TBI
DIY ECM Mods
Iroc Rims
Chameleon Head Unit
Pioneer 6X9s
Eibach Springs
KYB Struts
Edlebrock Strut Tower Brace
Wonder Bar
Lowered 1.5 in

I figure she weighs around 3300 without the auto, A/C, spare, and a buncha other crap i've trimmed off. I've already shown a buddy the light (he drives a mustang. hehehe )

 

And why is it the spark modules fault that the ESC code comes up?

RBob.

 

i dont think its the modules fault per-se. But from the seaches i've done concerning the topic i've come to the conclusion that running a 305 spark module with a 350 isn't the 'right way'. I was under the impression that replacing the spark module would set the system correct for monitoring the larger displacement motor.

As far as looking at the knocking from an old-school perspective, i never can hear it (although that doesn't say much - most detonation is silent) and i'm pretty sure it shouldn't be an issue. I'm only running about 9.5:1 comp and i always run 92-93 octane. The only time I get the code is when i just roll on the throttle from a stop or if i jump on it when i'm rolling. I can mash the throttle from a dead stop, spin it to 5,000 through every gear, and get no trouble. I dunno, i'm just throwing darts, but i figured this was a direction i hadn't traveled.

Ty

PS - i have changed the EPROM and done as much to suit the 350 as i can (bigger injectors, ect). The plugs are always on the rich side too, so i'm not running lean.

 

It sounds like the engine is failing the forced knock test. There are two tests the ECM makes for code 43. The first is to look for run-away knock. If this was the problem you would be getting the DTC 43 almost all of the time.

The second test is that during times of heavy acceleration (PE mode) the ECM advances the timing to force detonation to occur. If no knock, then DTC 43. Your tuning and choice of octane have precluded the ability of the ECM to force the knock.

RBob.

P.S. the spark module (or ignition module) is in the distributor and is part of the EST system.

The knock filter is on the firewall and is part of the ESC system.

 

okay - so (not to be dense) do you think i stand anything to gain in replacing the knock filter? (what's the actual name for it? I thought it was the ESC: electronic-spark-control).

Ty

 

If you are running the '8746 ECM there is a patch that eliminates the forced knock test, highly recommended. (see 'patch method demo' thread on the DIY PROM board).

If you have an '8063 then I'm not too sure what you can do. I've thought that it would be possible to put a momentary push button switch in line with the knock signal to the ECM. After the engine has been running for a couple of minutes push it a couple of times to signal that knock is occuring. That should be enough to fool the ECM into thinking that the ESC sysyem can sense knock.

RBob.

 

Just buy the 350 ESC moudle that goes on the firewall IT will take care of your problam. It took care of mine. It's about 50 dollars at your local part's store

 

Knock Sensor: 10456288
ESC Module: 16128261
These are the correct #'s for the 350 sensor and module.

http://www.gmpartsdirect.com/
has the best prices I've seen.
-Rich-

 

Rbob - I'm running the 8746 with a 'custom' EPROM that i had someone from the boards program - so i wouldn't be able to apply the patch on my own i'm pretty sure. Could i still get somewhere by replacing the knock filter?

Ty

 

If the new knock filter is better able to discern the knock (if there is any) from the forced knock test, or, if it reports false knock, then it will clear up the code 43 problem.

RBob.

 

Just like I said before, Get a new 350 ESC Moudle

 

If anyone is doing the junkyard search for a knock module the 3 letter code for a 350 module is: HKR

This is printed in big letters on the label (HKM is a 305).

Can look in Caprices and in full size vans/trucks.

RBob.

 

hey guys - i've been getting that code 43 again which i started this thread for - and i came across something of a revelation:

Rbob - you said to me that my octane and tuning aren't allowing the computer to force a knock, which is pushing the 43. This week I went from running 92 octane (under which the motor rarely gave me the 43) to running 94 (I thought I was doing myself a favor!!!) and now the code appears more often. Thats the only thing i've changed on the car other than the weather i drive it in - its 90ish now instead of 70ish, and i am forced to believe this is my problem. Any input guys? What do most of you 350/TBI guys run for octane?

Ty

 

Try backing the timming down a couple of degs and running a tank of 89 oct gas and see if that changes anything.

Steve

 

The timing right now is set where the factory would have it, so i'm going to try running a tank of 89 once this 94 burns its way down. I hope this helps. It'd be nice to find a solution that SAVES me money. haha



Ty

 

RBob,

Is there generally an advance limit for the ESC test (DTC 43)? It seems to me that the ECM will advance the timing a max of, say, 5 degrees past where it is in PE, briefly and if no knock is heard, it sets the DTC 43. That would prevent the ECM from killing the engine if the ESC is actually not picking up the knock (or the KS itself).

I ask because a few months ago I started tuning an L03 in a 91 Caprice ('6965) with an LT1 cam. He had his timing set at stock, I think (0d BTDC), and he was getting DTC 43 along with a huge power decrease. I went in and added a bunch of timing in the main spark table and his DTC 43 went away. Does this make sense?

 

I replaced the knock module (ESC) when I did my changeover because I experienced a similar problem to yours with my setup. The guy, Rich92rs350 helped me out a TON and anything he said was correct. I think this may be your only problem, or perhaps, your knock sensor is bad??? If you have a voltmeter, check out the current ESC and the Knock Sensor, see if the values are correct.

 

The '8746 ECM will not have PE or highway SA until the code 43 test passes.

The code 43 test is first attempted with an added 14 deg of SA (ANLU cal). If it passes, cool, if not, then it is again attempted but this time with 20 deg of added SA. If it passes, cool, if not code 43 is set.

Another thing/item that is in effect is that the distributor can only advance the SA by 42 degrees. So there is an upper limit to the amount of total SA during the knock test.

As others have stated a different knock filter may fix the problem. A few counts of false knock will also fix the code 43 problem.

Me, I don't like my high performance engines to knock (or low perf ones for that matter). So I have developed code patches to eliminate this stupid test. It truely is the best way to go.

If you want to test the ESC system hold the idle over 1200 RPM and rap on the block with a plastic mallet or broom handle or such. The RPM should drop as timing is pulled out. Engine needs to be at normal operating temperature. Can also do a WinALDL log at the same time for a later review.

RBob.

 

RSCamaroguy92 - when I did my swap I did install a new 350 knock sensor (I think it was a 350 unit...) as well as the 350 knock filter, but is there anything that could have affected the sensor, say - if i possibly overtightened it or something? It does seem odd to me that I'm dealing with this stupid knock problem only when i run higher octane, but thats all i can figure.

Rbob - If i was to have this patch (which eliminates the heavy-acceleration knock test) applied to my chip, would it be possible that it would eliminate the code?

Ty

 

Yep'r, no doubt about it. The patch sets the status bit just the same as if the test was run and passed. So the test is never run (ECM thinks that it already has), and you have PE and highway SA right off.

If the patch is applied and you still get a code 43 malfunction then the ECM is getting what is known as run-away knock. In this case the knock is continuous. An open wire/connection between the ESC filter and ECM will cause this error.

RBob.

 

Does the 7747 perform the knock test also?

 

Yes.

RBob.

 

very intersting. today i had a friend run his scan-tool on my car and i realized i had a code 51 in teh car from when i tried a bad eprom - after clearing the code the 43 only appeared once after a heavy romping session (it feels like if i dont commit to full throttle and ease off (like when attempting to jump out of traffic or something) the code still goes off. I can push the car otherwise and it won't happen. I think its just a little quirk in the car - but i really want to eliminate it. I dont really have the time/knowledge to do this myself, so how can i get the patch in my chip?

Thanks guys

ty

 

Maybe your "leaning out" the car???
Have you put an adjustible fuel pressure regulator on the car? I know some ppl say you can get away without one, but I definitely gained ALOT by doing so, also this will help get rid of any knock due to detonation in leiu of a lean mixture.

 

nah, i'm definitely running an AFPR. good idea tho


Ty

 

So......

My truck must not be performing the test, because I never get a code 43.

I only have 8.0 CR, but normally run 93 octane.

I'm using the 8747 ECM.

The truck runs great up to around 4200; between 4200 and 4600 the RPM's dip, then it resumes pulling hard again.

So what is faulty, the ESC module, the knock sensor, or the ECM?

And is it correct that it performs this check everytime it goes into PE?

Something is at fault because I've experimented with up to 20 degrees initial timing with an off the shelf chip and the stock one; never got any codes.

What is the effect if I ground the wire to the knock sensor? If it fails the test, will it allow PE with full timing?

Thanks for the clarification!

Bill

 

When you said '7747 you had asked about the 1227747 ECM & code. As far as the '8747 I have absolutely no idea about how it operates. I have never seen that ECM or the code it runs.

As for the DTC 43 forced knock test on the '747 & '8746 it is only run a maximum of twice. It either passes or fails (and sets the SES).

Once it passes, it will not be run again until the next key-off/key-on happens.

Grounding the wire to the knock sensor will disable the detection of detonation.

RBob.