Electronic Spark Module ... future MY 90 Achilles Heel?
 

While browsing parts for my cars on EBay I noticed a part there in the mix I never noticed before. I have been driving my 1991 ZR-1 for 12 years now however just over a year ago I bought a 1990 ZR-1. A few of you know that the MY 90 had a few differences technically that did not follow into the different model years as the electronics and the engines for that matter improved. While almost everybody knows about the ECM and the DIS that are failure points along the entire model run I propose that I have stumbled upon a MY 90 potential problem area that I was completely unaware of. While I am fairly knowledgeable about ZR-1s I will be the first to tell you I know several members in the community that have probably forgotten more than I will ever know lol.

The ESC is also called the electronic knock module. It provides an modular interface between the knock sensor and the ECM. On earlier C4s it was located near the evaporator housing and in the 90 ZR-1 it is located on the evaporator suitcase below the radiator high fill point. In 1991 ZR-1s and on later cars ESC was incorporated into the memcal in the ECM. When the ECM detects knock (pre-ignition), it will retard the timing to save the engine from damage. This will sometimes result in a loss of power and pinging and overall poor running conditions. Just like the MY1990 air bag frame rail sensors and the Air Bag DERM module the ESC I believe is a MY 90 ZR-1 LT5 ONLY specific part. I have no idea on availability of this item however I suggest as our cars continue to age that this might be an area of concern. I suggest if you can find one you add it to your parts store if you own a 1990 ZR-1.

I have personally not heard of a failure of the ESC However Usually a Service Engine Code will be thrown if it fails. If it fails "silently" your ECM will not be able to detect any pre-ignition due to bad gas, improper timing, electronic misses etc. and you may damage your engine if not replaced. There is one of these currently on EBay for sale that I advise may be a good item to stock away. Here is that EBay auction number 192441750427. (Not my auction and not affiliated in any way shape or form) just passing along the information.

The GM part number and interchange number is 16080211, D1931A

Just my thoughts your mileage may vary. GC

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

Yep.. Another thought is run 1991 ECM Code (repin the ECM) and figure out the key module then run the 1991 ESC..

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

-=JEFF=- lol while you are an electrical guru and this may be the solution I am glad I am not the guy trying to figure that out. Yikes

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

Easy.. actually I have it all marked out and I was going to try it (but with 1992 code an CCM)

I think the swap would be straight forward, another thought is to have someone look into the BIN code and find the 1990 stuff and 1991 stuff and integrate the 1991 ESC stuff to the 1990 BIN File..

Now I need to look at it again

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

Just looked..

Get a 1991 power switch ( unless you are bypassing it) I am sure I can figure out a way to use the 1990 switch for the 1991 design

run a new wire to the knock sensor and get a 1991 knock sensor.

Add the ESC board to the PROM.. Run 1991 code..
I think that is it..

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

Jeff,

Are u suggesting to use the 91 Mask for a 90 ZR? Is there a difference in the 90-91 sensor? I would think the frequency would be the same for any of the LT5s?


On a different vein, the ECM runs a forced knock test. Some info from RBob over at ThirdGen.

This is from ThirdGen.Org. RBob is a moderator there and a tuning guru among other talents.

“Code 43 is set by one of two different ECM tests. The first test is run-away knock. If within a period of 3.9 seconds more then ~245 knock counts are detected code 43 will be set. This can be caused by an open wire or a non-existent knock filter.
The other test is that the ECM will advance the spark timing in order to force knock (detonation). The ECM will attempt this twice, the second time with more advance then the first. If both forced knock tests fail code 43 will be set.
The forced knock test takes place under PE conditions. Once knock is detected PE and HighWay SA is now in effect and the forced knock test is done.
“Hook up a scan tool and check the knock counts. If the counts are constantly incrementing then you have run-away knock. You then have either an open wire or the filter is bad.
If after some spirited driving there is no knock and code 43 pops up, then either knock did not occur or the knock sensor/filter is not reporting it. If no knock is reported then test the system by holding the rpms > 1200-1400 RPM and rap on the engine block. This should be picked up as knock.
If so then you'll need to figure out why the ECM can't force the knock. Check the timing and the EGR system. Have you checked to see if the chip is stock? Maybe running 93 octane can do it?”

May need to check filter (ESC).

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

Yes.. biggest challenge will be to get the power key to function.. but I think it is doable

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

The addresses aren’t even close.

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

I know.. it will require 3 new wires on the 1990 harness..

- New Knock Sensor
- Power Key reference
- Power Key Light

I need to find the reference values for full power and valet. Also the Light on the 1990 DIC would get rewired. I can use an Arduino if needed to handle the logic change of the power key, if function is to be retained,

then just run Stock 1991 code in the 1990 ECM, I think the 1990 CCM should be able to chat with the 1991 ECM code..

Re: Electronic Spark Module ... future MY 90 Achilles Heel?
 

Not sure if anyone has noticed this but the module in question 16080211 is at least physically identical to the knock module used in the 84-86 Corvette 16022621. If we can verify that it is electronically identical we may have something. There may other versions for the 87 and up L98 as well. It’s a long shot but who knows. Here are photos of both.
H
:cheers:

16080211 for the 90 LT5

http://a63.tinypic.com/1zx5l5s.jpg

16022621 for the 84-86 L98

http://a68.tinypic.com/33vi2qw.jpg