Hey all, im new here after picking up my 03 Z06 last fall. After winter I pulled her out of her slumber in the the garage and had the ABS and TCS lights on the dash along with service vehicle soon message. I am also getting the following codes: PCM P1571, TCS No Comm, and SDM U1040. After some research I thought it was the ebcm module so I sent that for repair. When that didnt fix it I tried replacing the ignition switch. I've also checked all the grounding points, the rear speed sensors, the battery, and the fuses. Im at a loss at this point. Any help would be appreciated. Cheers

 

The U1040 makes sense for the EBCM no comm issue.....but not for the SDM. For a SDM no comm, you should have a U1088.

Before sending the EBCM for repair, did you cover the basics confirming 12v and ground to the EBCM ?

 

i did not check the voltage on the ebcm and I don't know what pins to check. I also didnt know how to read the codes before I sent the ebcm for repair

 

Do you have a DMM and a test light? Can you read schematics? If not, you'll have to find a trusted auto electric shop to troubleshoot further.

Assuming you at least check the relevant fuses...

 

I have a multimeter and I think I have a test light kicking around. Im an electrician by trade so I know a little about schematics lol

 

Pull codes again so you can confirm the SDM DTC.

Perfect ! Here you go.

 

You will have to determine which pinout you have on the EBCM depending if you have early or late production.

 

ok so I have 12.3v on the constant power to either ground and 12.2v on the ignition power on to either ground.

 

Good start. Make sure you load test the grounds.

 

ok I did this and they are both good.

 

Ok, and just confirming. The U1040 is s "C" current code or "no comm".....and it will not reset. You did not clarify the SDM code.

 

the SDM code is U1040HC

 

That does not make sense. Do you have a service manual for your car?

 

I do not

 

So there was more than one ask in post #11.

 

sorry maybe i'm confused. The SDM code is U1040 H C. The TCS is no comm. They will reset but immediately return

 

Ok. I'm sure someone will be along that can help you.

 

U1040 The DTC code U1040 for the GM C5 Corvette indicates a loss of communication with the Electronic Brake Control Module (EBCM). This can lead to issues with the vehicle's braking performance and safety systems. Common symptoms include loss of ABS functionality and illuminated warning lights. To address this issue, inspect the wiring harness and connectors for damage, check for corrosion, and consider replacing the EBCM if necessary.

The EBTCM required power on multiple fuses as listed in your specific schematic. The EBTCM also must have proper chassis grounds.

On top of each fuse are TWO fuse test points. With the ignition ON Engine OFF (KOEO) Read each test point to chassis or battery ground. Proper module operation requires each module to have proper VOLTAGE & proper CURRENT to that module/fuse. Connect a load to the test points to each fuse. An incandescing lamp like a headlight bulb works excellent. With the fuse under load, measure the voltage on that fuse. It should still be at normal battery voltage. Recommend removing each fuse and inspecting the fuse spades for corrosion, black oxide or damage. The fuses should fit very tight into the fuse box slots.

GROUNDS: Remove the large connector from the module. Find the two correct ground pins (F & G) on that connector. Read resistance (ohms) from that connector on both pins to battery ground. You should see very close to zero ohms. You can also load test that ground path using a test lamp. The test lamp lead should connect to battery POSITIVE and the other lead to each connector ground pin. The lamp should light brightly.


IF, you have proper grounds and proper power to that module, it should be working and communicating. If you have an O Scope, you can look on the serial data buss STAR CONNECTOR and see its signal data stream. In the passengers foot well to the left of the BCM are the two thin star data buss connectors. One has four wires, and the other has several (9) wires. The top of those connectors are a shouting strip that connects all the pins together. It can be removed to read each induvial signal wire to ground. The Star Connector with several wires is the connector with the EBTCM serial data wire. Pin E is the EBTCM serial data wire/pin. For most people, this is beyond their capabilities but, I provide the info just in case you are able to use it.

 

I reread your post and there is confusing information
The SDM = Sensing Diagnostic Module. It deals with the AIR BAG system. That should NOT have anything to do with the EBTCM.

TCS Traction Control System, NO Comm tells you that the BCM detected that the EBTCM failed to respond or communicate during the state of health request message. That is why you need verify:
1. You have propper Power on each fuse
2. You have proper GROUNDS on each module ground wire all the way back to the battery.
3. If power and grounds are verified GOOD, there needs to be the correct communications signal on the module serial Data output wire in the main module connector (Pin 21) to the Star Connector Pin E