Coil packs failing causing ABS issues.
 

It's an odd one.

I have an ABS failure that keeps arising. I replaced all the wheel bearings just to be safe, thinking the wheel speed sensors might be going bad. Did not solve the problem. So then, for whatever reason, I decided I was going to change out the coil packs. The ABS failure lamp went out on the AIM dash. For a handful of laps, the problem was corrected. ABS functioned normally. Maybe 15 minutes of driving, and the ABS failure code came back. I changed the coil packs again, and the problem was once again gone. My wife drove the car for an entire 20-minute session. No ABS failure. I drove the car for another 10 minutes, and the failure code came back. I use a higher RPM range than she does for a decidedly longer period of time, lap after lap.

I am thinking heat and/or vibration are causing the coil packs to have an issue. They are hard mounted directly to the valve covers. I am putting heat shielding in between the coil packs and the valve covers and putting them all on their own "pillars" to get them off the valve covers.

The problem with ABS failure is that these cars have horrible brake bias without ABS, which can cause premature lockup, especially at the right front. You can drive around the problem, but it's a little inconsistent and slow.

Is there anything else I should be thinking of that might be causing premature failure of the coil packs other than heat and vibration? I forgot to mention that, other than the ABS failure, the car runs perfectly. It does not affect the way the engine is running at all.

What ABS codes are set?

What makes you think the coil packs have anything to do with the ABS system acting up?

Because when they are replaced, the ABS warning light on the AIM dash goes out and ABS functions properly. If driven gently, it's fine. By gently, I mean under 6500 rpm shifts but still WOT pulls. Go out and try to go quick and the ABS failure returns after a couple laps. It makes it super hard to go quickly, especially in traffic, as you're always wondering when the ABS is going to stop working. When it does stop working, it's almost an immediate lock-up of the right front when you're pushing.

Looks like this. I almost collected the car in front in this instance. This was a wheel speed sensor issue, hence why that's where I started.


AIM dash tells you everything but just shows ABS failure and a blinky blinky red light of death. So strange.

It's in "failure" mode now, so I am replacing each coil pack individually to see if there is just one that is bad. My troubleshooting will get it narrowed down to which coil pack(s) are the issue. I still won't know the "why is it failing" part of it.

From your description, it sounds like new coils don't fix the problem. It comes back when the car is driven hard.

Are you saying that regardless of how long you let the car cool down, starting the engine with brand new coils is the only thing that makes the light turn off, even though it comes back? How many new sets of coils have you installed?

I think the next step is to retrieve the ABS codes.

Yeah, I highly doubt the coil packs have anything to do with the issue because if they were acting up you'd notice it with how the engine ran before anything else.

Also, you need a Tech 2 or similar type of scanner to read any EBCM codes as a regular OBDII scanner can't.

Yes, you can wait months, and if you change to new coils, the problem will go away. It has nothing to do with the temperature of the engine or surrounding components once the problem arises. It does not go away on its own. I know this because I assumed it was the hubs. I, of course, replaced them all one at a time, checking the whole time to see if it fixed the issue. Did not fix the problem. Luckily, the failure shows at idle on the dash.

Then I remembered that the problem went away when we switched to new coils, so on that hunch, thinking, WTF do these have to do with the ABS system, I switched them again at the track, and bam, problem gone. If you do not change coils, the problem remains. I went through 4 sets. Original set, MSD set, OEM set and another OEM set. I have tons of coils now to go through and try.

The AIM system shows only the ABS failure. It does not give traditional codes like you would expect. Modules have been removed. ECU is what remains. The only thing the OBDII port is for now is to tune the engine with HP tuners via the ECU. The AIM download only shows ABS failure. There are no traditional codes like you would get from a Tech II.

I just don't know specifically what could be causing the issue with the coils. Is it a voltage issue and not a heat or vibration issue?

So I pulled the plugs, and they look great. I am changing them out just because. I ran the part number, and they are racing plugs. So my dumb ass thought that because they were marked with an R, they were resistor plugs. R5724-8. Upon further research, it appears that they are not.

NGK Racing Series plugs are engineered to withstand the harshest engine conditions. Special insulator nose configurations improve throttle response. Corrugated ribs prevent flashover. Pure alumina silicate ceramic insulator, provides superior strength and better heat transfer. Copper core aids in heat removal. Triple seals prevent leakage.

Resistor No

Is there any possibility that this "noise" is causing some kind of electronic interference? Years ago, I had issues with non-resistor plugs and a Haltech EMS on a different car. Maybe the non-resistor plugs are screwing things up?

The ones I have arriving today are the same 8-heat-range OEM-style resistor plugs. I am also switching out the plug wires for new ones, just to be safe. See what happens.

NGK IX Iridium Series plugs were designed specifically for the performance enthusiast. Fine wire center electrode ensures high durability and a consistently stable spark. Iridium alloy has an extremely high melting point, perfect for today's high-tech, high performance engines.

• Trivalent metal plating provides superior anti-corrosion and anti-seizing properties
• Corrugated ribs prevent flashover
• Pure alumina silicate ceramic insulator, provides superior strength and better heat transfer
• Copper core aids in heat removal
• Triple seals prevent leakage

Resistor Yes

Is it throwing the "Service Active Handling System" message? When my car developed a mis-fire, it threw that error message simultaneously. Apparently it's GM's pointlessly linked error codes. Mis-fire = active handling problem?!?!

Nonetheless, I did have a LEGITIMATE mis-fire.

Is that what got you onto swapping coil packs? Have you dug any further into what your ignition problem(s) may be, other than coils??

So with this thing, there's always something going on. Up to this point, misfires have only been caused by burned plug wires. I guess the ARH 2" get hot and they just melt the plug wires. Huge PITA but easy fix. Just carry a ton of plug wires. Back out in minutes. Definitely NOT an endurance car.

So remember, there are no "codes." It no longer has any active handling, no factory dash. The only thing left is the ABS and a factory ECU we use to tune the engine parameters. The reason we changed the coil packs the first time was because they were a non-oem coil pack and everything was a little wonky. We figured, let's just remove that variable and change them out for OEM. The ABS issue went away. The car also made 33 more horsepower with OEM coils. Nothing else changed other than freshly lashed valves. I drove it for 20 minutes on the track after this dyno session, and the ABS problem was back.

https://cimg7.ibsrv.net/gimg/www.cor...9d0866ea37.jpg

This is the car with no ABS and the blinky, blinky red light of death on the AIM dash. It ran pretty well. I am just careful as hell and brake, literally hundreds of feet early, which sucks.



So I have been just living with the problem and driving around it. My wife doesn't even know the ABS isn't working. She could run thousands of laps in the thing without any issues.

If identifying the bad coil pack(s), taking heat and vibration mitigation measures, spark plug wires, and proper resistor spark plugs doesn't work, it's possible that I go down the road of having the ignition system rewired. If that happens, I will just opt for a Motec and a stand alone ABS system. Then the problem will be solved. The Motec TC is super slick and works better than my right foot does so I am fine with that. The Bosch ABS is also far superior to the factory ABS.

You have a stock EBCM on the CAN (GMLAN) bus, right? Attach a GM ABS-aware code reader to the bus and retrieve the DTCs.

It does still retain the EBCM.

I apologize for my ignorance but the only way I've ever attached the Tech II or any code reader is via the OBDII port which no longer makes a connection. Which code reader would I need and if not through the OBDII port how do I connect it to read those codes?

​​​​​​All of the information that I pull now I get from the AIM system. I hook the laptop to the AIM dash and I download all of the information after each session. It's very possible that I am not adept enough at using Race Studio 3 to see the ABS parameters being captured during the data logging. I'm going to go back through the downloads and see if I'm missing anything.

HP Tuners can see the ECM through the DLC (the OBD2 port), but when you plug in a Tech 2, it doesn't work?

A stock C6 has a single CAN bus (GMLAN) that goes from the BCM in the passenger footwell to the EBCM to the ECM under the right front fender, with some other optional stuff in between. The CAN bus is broken out on pins 6 and 14 of the OBD2 port, which is wired to the back of the BCM. If you can see the ECM from the OBD2 port, you should be able to see the EBCM.

I don't know what's been done to the car - is it possible the OBD2 port power pins are no longer active? A Tech 2 will require external power in that case.

I have not connected a Tech II yet. My other reader powers up but there's nothing to read. No connection can be made. I have used it countless times for analyzing and reading codes in multiple GM vehicles in the past, including this one. I have not used it, nor have I been able to since the change was made to go to the AIM dash.

The OBDII port is used to give HP Tuners access to the ECU.

The BCM has been removed.

Everything has been rewired, the harness stripped for weight savings, and anything that is not being used has been removed. OBDII power pins are active. The reader powers up instantly when the main power is switched on.


So after some lengthy conversations today, we are all in agreement that, for whatever reason, this is spark plug, plug wire, and/or coil pack-related. I know I can get the ABS problem to go away, at least temporarily. The ABS failure light will go out, and there will be no more wheel speed blips when the car is idling and stationary. It shows right on the dash in real time. Unfortunately, I have to take the shitbox to the track to figure out if my attempted fixes have actually worked.

There are only 2 things left I had intended to have done at some point, and those are the Bosch ABS and the Motec. Going to happen at some point. It's just a matter of when.

Yes, non-resistor plugs can cause issues. That's an easy change to make and test. I have used non-resistor plugs before and had no issues. But I also had my coils relocated to the fender areas.

I may be going a little overboard, but I have a new set of coils on the way, new RFI/EMI suppressing wires, new resistor plugs, insulation under the coils atop the valve covers, and I am wrapping the headers. The valve covers I use have the coils fastened directly to them in some cases, so I have lifted them off the valve covers just in case there was some kind of vibration getting to them. I have sandwiched DEI coil pack heat shields in between the valve covers and the coil pack risers.

I am also doing some exhaust work, and the car will be running today, so I can at least see if the spark plugs and wires solved the problem or if the coils are bad. New coils should be here on Monday.

In the picture below, you can see how it was. In any case, it goes out for testing on May 27th at a track I am familiar with, which is close to home and just a short tow when it's still messed up. :D

https://cimg8.ibsrv.net/gimg/www.cor...76e3c90baf.jpg

Oh, you're not using OEM coils? Did you recently make the change to those coils? Did the issues start after changing to those coils? I would recommend going back to OEM coils as well.

This car has been plagued with a series of electrical Gremlins since I did the first build back in 2015. Unfortunately they were mechanical issues that needed to be addressed which took the attention off chasing down the electrical issues. At that time I had OEM coils.

Next build, more electrical issues. Always service active handling or TPMS or whatever. ABS had a problem one time but new SKF hubs solved the issue. Car always ran perfect. That's when I know the engine had racing spark plugs in it. It always ran great so I just didn't think about the spark plugs. Always used OEM coils.

With this build I thought the yellow looked cool 😁 and figured how bad could they be. The ABS started acting funny after the car had been completely rewired. When we switched to OEM coils which is what is on it now the ABS problem went away. Unfortunately after just 20 minutes of track session driving the problem returns while using the OEM coils. The car always runs perfect. If the car had a non-abs racing brake system in it I would never know there was any issue, ever.

So now I have a new set of OEM coils arriving Monday. In the meantime I'm just going to start the car today, if I have time to get an oil change done prior, and if that happens I will see if the spark plugs and the wires made the difference or if the coils are bad. If the error message is still showing once the new coils arrive I will change them out one by one and run the car and see if it's one coil or two or all of them that are bad.



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Ahh I see. Sorry, I had skipped some of the posts and could have found my answer. I have a short attention span sometimes, lol.

Check all your grounds too. Maybe even add 1 or two more. I recently had an issue with my car that had to do with a ground wire that I moved. My car is on a holley but the factory ECU is still there to control the dash and keep the starter button functionality, etc. I was moving the battery around and changed one of the ground locations. I was having issues with the laptop disconnecting from the ECU and erratic TPS issues that were not allowing the engine to start. Moved the ground back to the engine/head and all those issues went away.

I would try to add another ground from the engine to the frame and from the engine to the battery directly.