Backstory: 2002 z06 115k miles. Clean texas car with zero rust. All grounds have been gone through and checked for resistance and grounded to chassis. All ground points have been inspected and cleaned. Serial wire to the bcm has been checked for resistance and passed. ABS unit has been sent to absfixer and bench tested to ensure proper function. 12v constant at the abs unit is good, along with 12v key on. New red top battery as well. All fuses have been replaced as well.

Problem: ABS and TC lights, no codes except 1040u and TCS No comm. The interesting part is that my abs WORKS, however the lights are still on. I have tested this by unplugging the abs module and sure enough once i plug it back in the abs unit is working.

Starting to lean towards maybe the cluster being bad? Thoughts or suggestions?

 

Well anytime you have “no comms” you always check that modules power and grounds !!...as you can see pins A B are your “hot at all times” and B is your ignition feed for your 2002...I always check power (and grounds) at the module with the harness plugged in and back probing the connector...now you can see there are 2 EBCM grounds...pins F and G...how exactly do you check grounds ??...resistance checking of grounds is NOT the correct way !!...you have to “load test” your grounds !!...I use an old headlight bulb of various sizes depending on how much current that module may draw....positive lead of bulb to battery positive and negative lead of bulb to whatever ground wire that needs checking...light should be bright if ground is good...have BOTH been checked ??...G103 near the BPMV and I believe it is a braided ground connection...G108 is near the battery tray...also the serial data wire does not go to the BCM...all of the modules data lines connect to 2 “star connectors” which are located near the BCM...you should remove the “comb” on that star connector and make sure that is shiny clean...also make sure that the terminal it plugs into is clean also...you don’t use resistance to check the serial data wire which is a light blue wire at the star connector on your 2002...you really need a scope to check the data line...with scope you’ll see a 0-7 volt square wave but I have checked the data line with my DVOM and all I see is a fluctuating voltage of less than 1 volt... I think I saw .3 to .4 volts...If you see ground or 12 volts on the data line that is not good...we recently had a member with a PCM no comm and he found a bad PCM ground...that fixed it !!...a scan tool that can see all the cars modules really helps in diagnosing...code readers don’t cut it !!

 

This question might be irrelevant, but why would the ABS work if im still getting no comm issue?

 

The 2 combs on both Star Connectors tie in all the cars modules together and allows one module to communicate with another...kind of like a bus bar...maybe that comb (pictured below)

on that EBCM serial data line (light blue wire) may have corrosion on it !!...the star connector with the 8 or 9 wires should have that light blue wire on it !!

 

I just looked at mine and it has zero corrosion, its also worth noting that all of my ground packs are in similar shape. I found zero corrosion.

Something else i just remembered, my low oil level light keeps coming on. I did a have a cut in the ground block on the wiring harness close to the battery. I fixed that, and replaced the sensor itself to no avail.

 

I also have no idea where thesr 3 wires go

 

I can remember a few years back a member had some no comms...he said the combs looked ok but when he cleaned them up with some sandpaper it was good again !!...just clean them up a little !!

 

Don’t know what that may be ??...that’s inboard of the battery tray.

 

I sanded the grounds, the combs and even added an additional ground on both ground packs by the headlights and attached it to the block. No luck

 

Even intalled a known working abs unit from my other z06 and still have the tcs no comm.

 

OK, try this !!...remove the comb on the splice pack connector with the light blue wire...5th wire from the end (Pin E)...with key on see if the voltage fluxuates around .1 to .3 VDC...now disconnect the battery...measure the resistance between that light blue wire and ground (I used one of the door hinge bolts....you should see around 150 K Ohms...my pics below !!...if that blue wire is broken between the EBCM and the splice pack you will get a no comm !!...try that !!

 

Voltage reads .11

Ohms are at 1 (infinity)

I grounded to the door hinge bolts

 

Scratch that, I did it again and got 190k ohms

 

Is this TCS no comm a “H” or “C” code on your scan tool or through the DIC ???...if it’s an H just clear it and see if it comes back on the next ignition cycle before you turn the key off !!...so are the TC/AH lights still on ??

 

No comm and 1040u are current codes, abs and tc lights are on. Ive reset it thousands of times by now.

I have 2 z06s right now, my other has working abs/tc with no codes. If there are certain parts i can swap over let me know, i have an entire car at my disposal.

 

So I believe you said TC/AH are working ??...did you stomp on the brakes going down the street and actually felt the ABS functioning ??

 

I dont know about tc, but abs is 100% working.

 

Maybe it’s the IPC...I’m stumped as to why you still have the “no comm” if the ABS/TC is working normally and we saw that the module is communicating on the data line...if you had a Tech 2 you can be looking at some of these Data Pids below...


if the EBCM is commanding the ABS/TC lights on you can see this on the scan tool !!

 

What is the ipc?

 

Instrument Panel Cluster !!