Electronic Spark Control Module (ESC) Help!


I have been getting false knock on my car. I traced my trouble to the ESC module...the resistance values between the 5 pins are outside of spec.

Since the stock 87 ESC module is now next to impossible to find, I decided to look around.

I have seen many cars in the junkyard that have these identical modules on them, however they have different codes stamped on them and are different part numbers.

I realize that the ESC amplifies what the knock sensor "hears", then sends the data on and cuts timing if need be.

Does anyone know what the difference is inside between a 87 GN ESC vs a 87 Caprice (for example) ?

My local yard has an 84 N/A regal 231v6 and an 86 Riviera N/A 231v6...I was thinking about grabbing the ESC modules out of those cars. But then I thought, this is a pretty important sensor, if it isn't sensitive enough...kaboom!
Why don't you just try some of them? I doubt it will cause you a problem. Maybe it won't fix your problem because your problem is elsewhere.
The ESC is a frequency filter. It looks for a particular frequency that is predetermined to be knock and sends a signal to the computer. Different modules look for different frequencies. The codes on the modules are specific to a specific frequency range. Who knows what those ranges are :rolleyes:
I hear ya...but wouldn't you think the frequencies emitted by an 86 Riviera with a 3.8 V-6 would be the same as the 86-87 GN? Isn't it the same engine?
Well, that's the module you have. What other choice do you have unless you can find the specific unit. Come to think of it, Brian at Gbodyparts is bound to have one. ;)
Highway Stars has them new for the 86 at least.

HIGHWAY STARS - nos4gn Buick Grand National Parts 1986 1987 Buick Turbo Regal T-Type GNX parts

86 GN calls for a part number 16022614 and the 87 calls for a 16051654. The part number is etched into the plastic. If your going to search in the yards maybe one of those will work with that part number. I noticed the module will have the same part number but the sticker that's on it will read different letters on many I've seen.
Both BSK and HKN modules are a close match to the turbo modules (BLO & HKP). They are from 3.8l Buick carb'd engines. The gain is a tad higher with the other areas matching. Try the BSK first as that is a 4-pole filter while HKN is a 2-pole filter.

Thanks for the info...I will obtain a few of these and post the results of ohm testing the various terminals.

So this makes me think that the knock sensors really aren't all that different, it is just the ESC that filters different frequencies based on the type of ESC you have. Sound correct?
Hello. where would I find the values to check "87 ESC module #16051654? or better still, Who's got one they want to sell? Oh I know. It's the same guy that has a CAS V4 Sorry, not for sale! Later...
The ESC module is an analog electronic module. Can't test it by measuring the resistance between terminals. There are ways to bench test it by using a volt-meter or scope. Along with a knock sensor or frequency generator.

Can also test the module on the car with a warmed-up running engine. Hold the idle up around 1200 RPM and rap on the knock sensor. The RPM should dip a little and recover. Should also note the knock counts reported by the ECM going up.

To make things more complicated I have a MS3 for a ECU & we are seeing a dip in volts on the pnk/blk wire when the ESC is plugged in. Pnk/blk goes to 8v when ESC is plugged in, but the fuse doesn't blow. Not plugged in 12v. I'm guessing I have something wrong with my source power.

Do you know if I can plug a 87 ESC into a 86?

I'm just coming back together from a frame off restore, so anything can be open game for issues.
Hello. I am not familiar with MS3 computer, I run my factory ECM. However, the '86/'87 ESC modules are very similar with one being more sensitive to knock detection. I believe the '86 mod. [BLO sticker] is less sensitive to knock, more filters. With regard to your voltage issues. I would check all wires including all terminal ends for "conductor breakdown." and corrosion at the pins of the connectors. The pink/blk wire is the "data" wire. That's the one that goes to the ECM. Check that one as well. Also, and very important. Make sure you have a good ground. Unless you have replaced wire harnesses during your restoration. That wiring is 30 something years old! Hope that helps you.


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the 86 esc module BLO sticker is more sensitive to knock .. it is a 2 pass filter... the 87 esc module HKP is less sensitive ..its a 4 pass filter ... they chaged after 86 for various reason i cant remeber right now.. will have to ask Anthony P or clark on that explantion... i believe just because the 86 is more sensentive does not actually make it better .. they switched bc the 4 pass was better suited to the LC2 motor....more on this later
@RmvBfrFlght and @mikestertwo are two key individuals whom I'd say are experts on this topic. over the years, both have provided excellent input. so there is no need to retype what has already been said.

grassdoc asked what I knew about the spark control module and their variations with all the different stickers and part #'s found on so many GM cars. What's interesting is that in many archived threads on the topic, folks confuse the ignition module (under the coilpak) with these electronic spark control (ESC) modules. Below is from my own archives on the topic.

From the service manual:

Electronic Spark Control (ESC)

This system uses a Knock Sensor in connection with the Electronic Spark Control (ESC) Module and the ECM to control spark timing to allow the engine to have maximum spark advance without spark knock.

3.0L “N“ SERIES; 3.8L “A, C & H” SERIES
Circuit Description:
The ESC system is comprised of a knock sensor and an ESC module.
The ESC module sends a voltage signal (8 to 10 volts) to the ECM. When the sensor detects detonation, the-module turns “OFF” the circuit to the ECM and the voltage at ECM terminal “B7” drops to 0 volts. The ECM then retards EST as much as 20* in one degree increments, to reduce detonation. Retarded timing can also be a result of excessive valve lifter, pushrod or other mechanical engine or transmission noise.

A loss of the knock sensor signal or a loss of ground at the ESC module would cause the signal at the ECM to remain high. The ECM would control ignition timing (EST) as if no detonation were occurring. The EST would not be retarded, and detonation could become severe enough under heavy engine load conditions to result in pre-ignition and potential engine damage.

Loss of the ESC signal to the ECM would cause the ECM to constantly retard the EST to its max retard of 20* from the spark table. This could result in sluggish performance and cause a Code 43 to set.

Code 43 will set when:

with engine running: ESC input signal has been low more than 2.2 seconds.

It is interesting to note that GM's test procedure for the ESC circuit functionality is to bring the engine rpm to 1500 once engine has reached normal operating temperature. Then, strike the engine block in the area of the knock sensor. If the rpm drops, the electronic spark control module circuit is operating correctly. manual does not specify how big of a hammer to use.

On this forum, RemoveBeforeFlight and Mikestertwo have succinctly reviewed this subject matter previously. It's best to cite their posts on this topic, including the above from RemoveBeforeFlight - no need to type what has already been said well. Below is compiled for convenience in one thread.

1June2010 - mikestertwo:

"The ESC is a frequency filter. It looks for a particular frequency that is predetermined to be knock and sends a signal to the computer. Different modules look for different frequencies. The codes on the modules are specific to a specific frequency range. Who knows what those ranges are "

REFERENCE: https://www.turbobuick.com/threads/electronic-spark-control-module-esc-help.320257/

15March2008 - mikestertwo:

"It's rare that module goes bad. What your most likey seeing is false knock coming from some other source. Need more info on the car. Is it all stock? What chip is in it? What mods does it have? Assuming the knock is false it could be coming from the down pipe touching the frame, cracked flexplate, valve train noise, ect."

REFERENCE: https://turbobuick.com/threads/possible-esc-problems.244547/

2June2010 - RemoveBeforeFlight:

"Both BSK and HKN modules are a close match to the turbo modules (BLO & HKP). They are from 3.8l Buick carb'd engines. The gain is a tad higher with the other areas matching. Try the BSK first as that is a 4-pole filter while HKN is a 2-pole filter.

REFERENCE: https://www.turbobuick.com/threads/electronic-spark-control-module-esc-help.320257/

1November2016 - mikestertwo:

"The difference between the BLO and the HKP modules is the HKP module does not attenuate (reduce) the knock frequencies as much as the BLO module which results in a broader frequency band it passes through. The program in the computer chip is the same for either module. The way the chip identifies knock is the number of knock counts from the ESC module over time. This means the chip must see a certain number of knock counts from the ESC module in a certain period of time. The HKP module will pass more knock counts than the BLO module for the same condition. "

"The HKP will pass more knock counts to the ECM which would make it more sensitive than the BLO. "

14November2016 - BEATAV8:

"the knock sensor is a piezo electric crystal which responds to frequency. messing with the grounding can interfere with the frequency which the sensor "thinks" it sees. this is just my opinion.....

if there's absolutely no grounding at all, then yes there should be no signal whatsoever and the ESC should report 9V all the time, no knock retard and no knock counts. Same as having the knock sensor unplugged. "

REFERENCE: https://turbobuick.com/threads/esc-module-question.445071/

6December2013 - RemoveBeforeFlight:

"Don't go by knock counts, go by knock retard (spark retard). The reason is that there can easily be knock retard without the the ALDL link or the PL showing additional knock counts.

This will occur because the knock counter (PA3) is a 16-bit value (2 bytes). Both the PL and the ALDL link only show the upper byte of the knock counter. There can be several degrees of knock retard with no counts showing.

This is why the knock gauge goes full red when the PL is only showing a count or maybe two. The lower byte (LSB) of the knock counter is incrementing, with spark advance being reduced (knock retard), but the upper byte (MSB, the one we see) hasn't moved yet. Need to get 256 counts before a single count gets registered on the upper counter byte.

How the ESC system (electronic spark control, the knock retard system), works at a hardware level is: there is a 16-bit (2 bytes) hardware counter that runs when the ESC filter reports knock. It runs are 64 KHz, or, 65,536 times a second. The signal from the ESC module is basically digital, it just goes low when reporting knock.

The lower byte (LSB) of the counter, the one we don't see, increments first. After 256 counts then the upper byte gets incremented (MSB), the one we see, to actually report something. The lower byte then rolls over to/past zero and starts over.

In that time the ECM can be pulling spark advance. I say 'can' because under various circumstances knock retard can be held off. "

REFERENCE: https://turbobuick.com/threads/how-many-esc-counts-is-bad.404845/

Just the operation of the starter motor can add a value to the knock count register.

Following the conversation with grassdoc, I wondered if anyone has specific knowledge of the frequency response of the various modules. Has anyone setup a frequency/function generator, oscilloscope, meter, power source, etc. to simulate "knock" from the sensor in an effort to capture the specific workings of the different modules? How do they compare? I contacted a couple of electrical engineering & electronics hardware folks I thought could shed more light on this topic.

GM was pretty tight-lipped about the specificity of the knock frequencies for each engine's module. It's a pretty crude concept but was effective at reducing the possibility of owners using the cheapest gasoline (lowest octane) and damaging the engine while under warranty. Again, it's really rare for this module to fail, unless it is physically damaged.

While the GNX instrument cluster face stated "PREMIUM FUEL ONLY," there was no such notation on the other turbo buicks. From the engine service manual, the achieved (underrated) performance figures for the 86-87 LC2 engine were the result of minimum (research) octane rating of 91.
Buick 3.8 octane requirements.JPG

With folks today rebuilding engines for 500, 600, 700 horsepower on a street car, the original engine's harmonics have changed. Different pistons and/or rotating assemblies, use of aluminum heads, different valvetrains, the clickety-clack of roller lifters and their dog-bone connectors, timing set replacements (nylon coated cam gear didn't trigger knock sensor), all changed the harmonics of the original engine as delivered. Today, those operating at these higher horsepower levels most likely have XFI or the GN-ecu to better tune.

Even a stock rebuild using different (forged) pistons will change the harmonics. How much? I don't believe anyone knows. And we don't know the specific frequencies for each module. So we carry on with the knowledge mikestertwo and RemoveBeforeFlight have shared regarding this topic.
Both BSK and HKN modules are a close match to the turbo modules (BLO & HKP). They are from 3.8l Buick carb'd engines. The gain is a tad higher with the other areas matching. Try the BSK first as that is a 4-pole filter while HKN is a 2-pole filter.

question you might know i have one with an HKD sticker on it ... and was wondering if you knew anything on it ..maybe 85 turbo riveria ???
Additional info for above....HKD sticker was on 16049534 - might be from 3.0L, 2.8L V6 or smaller 4-cylinder FWD . turbo Riv should have 16022614 BLO module as it's the same hot air engine as 84-85 turbo Regal. but i defer to RemoveBeforeFlight and Mikestertwo.