Knock counts of 255 all the time???

[steveman09]

Anyone ever run into the knock counts stuck at 255 all the time with the key on engine on or off?

I have knock feedback disabled because of this, have tried 2 different knock sensors, triple checked wiring from the knock sensor to the PCM 0.2 ohms of the wiring and the sensor ohms out good as well?

The PCM im using is the 16197427 with $OE mask.

I've been told the memcal could be bad?

The memcal is from a 5.7L truck and my truck is a 7.4L motor but has been retuned with TunerPRO and is using the Moates Ostrich 2.0.


help...

[jim_in_dorris]

Okay, until someone with more knowledge than me replies, here goes. The 5.7 memcal is expecticing a 5.7 knock sensor. I'm guessing you are using a 7.4 knock sensor. It might be easier to use a memcal from a 7.4 than to try to get a 5.7L knock sensor to work correctly in a 7.4L motor. Just speculation on my part, but I am sure that someone will chime in soon with a more definitive answer.

[RobertISaar]

are you showing knock retard along with the elevated knock count?

the knock counter increments when there is knock, if it's staying at the same value, then it's either a definition issue or something in the BIN isn't quite right, perhaps the wrong value being transmitted in the datastream for example.

[dave w]

Using information from RockAuto, a 94 K3500 7.4 liter has a couple different part numbers:
Standard part number is KS7 for manual transmission, which if I remember correctly is a 100K ohms.
The Delphi part number AS10016 does not indicate manual or auto trans, but using the Standard Ignition part number interchange website AS10016 cross references to a Standard KS6 which if I remember correctly is 4K ohms.

The RockAuto website shows for the 94 K3500 with a 5.7 liter Standard KS7 is Manual Transmission, and KS6 is for Automatic Transmission.

As a what if, maybe install a 100K resistor between the knock sensor wire and ground and turn the key on? Maybe $OE needs 100K? I'm thinking $OE was used for 4L80E transmission with either 5.7L or 7.4L.

Maybe the $OE .bin you have is set for manual transmission and the knock sensor is for automatic transmission?


dave w

[RobertISaar]

don't quote me on this....

but IIRC, MOST if not all of the manual trans applications used the 7747 instead of the newer PCMs, right?



steve, what is your sensor ohming out to?

[dave w]

I think by 1994 GM went with ECM 16196396 for Manual Transmission, which is very similar to the 1227747 (2732 Chip)?

dave w

[RobertISaar]

based off of a quick google search, it would seem you are correct. apparently it's nearly identical, probably just some different code in the ROM, which apparently is what differentiates a lot of the C3 ECMs.

so, if i had to guess, i'd say that ECM would want to see an external ESC module with a 100K sensor.

[gregs78cam]

so, if i had to guess, i'd say that ECM would want to see an external 7.4L ESC module with a 100K sensor.

You are correct, I fixed it for you. Manual = KS7, Auto = KS6 regardless of cylinder, which would be a matter of getting the correct filter circuit.

If you want the right filter for the correct knock sensor, I would think you would want either the 7.4L memcal (for use with the KS6), or the 7.4L external ESC (for use with the KS7), but I think you would need to bypass the knock circuits in the memcal to do the latter.

Am I wrong?

[dave w]

$OE is for the newer TBI PCM, the knock sensor should be 4K ohms. I'm not sure if having the .bin file set to manual transmission is a problem or not?

dave w

[gregs78cam]

$OE is for the newer TBI PCM, the knock sensor should be 4K ohms. I'm not sure if having the .bin file set to manual transmission is a problem or not?

dave w

That is the way I would try to go, use the newer KS and the correct memcal. I don't think Trans selection has anything to do with Knock sensor.

[EagleMark]

Anyone ever run into the knock counts stuck at 255 all the time with the key on engine on or off?

I have knock feedback disabled because of this, have tried 2 different knock sensors, triple checked wiring from the knock sensor to the PCM 0.2 ohms of the wiring and the sensor ohms out good as well?

The PCM im using is the 16197427 with $OE mask.

I've been told the memcal could be bad?

The memcal is from a 5.7L truck and my truck is a 7.4L motor but has been retuned with TunerPRO and is using the Moates Ostrich 2.0.


help...

Man I'm glad I start with all matched parts.

I just ran an old log from a $0E 16197427 PCM with a 5.7L Memcal in a 345 IH engine and knocks counts started around 300 and went up to 450, no signs of retard.

When we did this and looked for the Knock Sensor we had to get an Auto Trans for 5.7L which is Memcal 4K sensor. The manual sensor was for the earlier ECM (chip not memcal) with ESC and a 100K Knock Sensor. That's the problem with that era is most manual trans used the old C3 ECM and auto trans was C4 PCM.

Then 16197427 type C4 came with $0E and a manual, so Knock Sensors were all 4K for Memcal Knock.

But his question was knock counts and no they should not be locked unless it never heard a noise! Hit the block with a hammer while running and watch knock counts!

Back to why it's so hard to figure out what knock sensor to get is..... just look them up on RockAuto or? 1995 5.7L and 7.4L Auto Trans uses the same knock sensor. 1995 5.7L and 7.4L Manual Trans uses the same sensor. We already know there are 2 differant kinds of ECM/PCM used and one is a 4k and one is a 100k, Manual trans used the old ECM but Newer PCM came in Auto and Manual... so the books are not accurate!

It's frustrating when earlier ECM had differant knock sensors for differant engine size! Now all knock sensors are the same for C4 PCM! Why? Because you need the correct Memcal with knock module for engine size!

So the correct answer is? Use the KS6 Auto Trans Knock sensor which should be 4k ohm and it will be correct for a Memcal and work. To be accurate for your engine you would need the 7.4L Memcal.

If you buy a Manual trans knock Sensor it will be 100K and not work with your Memcal.

I think...

[steveman09]

So finding a 454 tbi memcal for this pcm is proving to be impossible! I did find one on ebay for $250! which is a complete ripoff in my opinion. Anyways if anyone has one I will be glad to pay $50 or so but not $200+ at that point i would be half way to a better ecu solution.

Just to answer some q's on here the truck currently has the th400 trans and the ecu is set to MANUAL trans. Could this be the issue? I do have a 4l80e but its not swapped in yet, the harness is done and ready to go, just havent had time to install it. And my knock sensor is new and ohms 4k.

[EagleMark]

With the 4k knock sensor the knock circut will work with your 5.7L memcal. Just because the part is new does not mean it's good. Has to be diagnosed, have you tried to hit block with hammer to see if system is working?

Weather the 5.7L knock filter in Memcal is correct for 7.4L is information I have never been able to find? Because of what I stated above I doubt it.

Place a wanted ad and someone might have one.

You touched a subject in EFI systems that is not fully documented. I've shared what I know and how to make them work without knowing exactly what makes the knock filters in the Memcal tick and answered your question on knock counts.

But I did not want to end the conversation. Our conversation do go off track and with discussion we all learn but have to take care of orianal questions.

[dave w]

I've recently learned, that a '427 PCM will run an engine without a memcal, provided the .bin knock programming is modified and a Moates.net G1 adapter is holding the chip. I don't recommend removing the memcal, except to troubleshoot a problem like a constant 255 knock counts. I recently did a road side fix for a limp home failure, by removing the memcal and flashing a chip that had the knock disabled using a G1 adapter.

dave w

[PJG1173]

Yes I found out the hard way it will run without the memcal when the g1 is used. I opened mine to swap chips and found the memcal tumbling around in the PCM. I've since modified a memcal to house my chip instead of using the g1.