Alright ladies and gentlemen, I've currently got an issue that I can not seem to fix for the life of me. My car has been down for the past 5 months for an assortment of mods including a cam, s/c, and meth. After putting everything back together, a friend of mine was going to set me up with a base tune just to get it to my tuner to have it fully done. Here's the issue, upon turning the key over to accessories, my dash was flooded with errors for Reduced Engine Power, Service Traction Control, Low Fuel, etc. He then attempted to clear it by hitting erase and then move on to connecting with HPTuners. He kept receiving a "no comm" error. We thought it might be a low battery so out it went and charged over night.

Battery is all charged and installed, I put the key in, turn it over to acc. and I'm instantly flooded with notifications. It's pretty hot in florida so i roll down my windows (mistake that was) Went into the DIC to see the codes and i'm literally getting NO COMM with everything EXCEPT IPC and the windows won't go back up. Checked connections at the BCM, checked ground, checked fuses 16 and 23 (I believe) under the hood. NO LUCK!

any advice would be wonderful

 

This may help.
https://www.corvetteforum.com/forums...mmunicate.html
You don't need to have the Tech2or Kent Moore tool to troubleshoot, but it does make it easier.
iF you can communicate to the IPC you have power, ground, and data at the Data Link Connector.
If that is good you can remover the star connector 2 which has the least number of wires. This will disconnect some of the modules on the bus. If one of those is the problem you should be able to communicate with the BCM and PCM and other modules.
There is another thread where 8vette7 posted some good troubleshooting tips for this problem. See if you can find it with the search function.
I have some more info but I need to find it and get it posted.

 

Refer to the Pwr & Gnd schematic and check the appropriate fuses in The IPC fuse block in the passenger foot well.

Be sure to disconnect the battery when you are making any changes.

You can also disconnect data star connector 2 also in the foot well. That will remove the door control modules and seat control modules from the bus. If comms. are good to the remaining modules, the problem is one of those. After that you have to get creative. You can remove star connector 1 but you need to insert a jumper from the BCM to PCM. pins. If Comms are good, it is one of the other module on that connector.
You need to find the offending module through the process of elimination.
When you find the module that is causing a problem it does not necessarily mean it is bad. It could just be a shorted wire, but you need to get communications working before dealing with that.

 

This is not the thread I was talking about but it has some of the information. It has some pictures of the star connectors and some troubleshooting tips from 8vette7.
https://www.corvetteforum.com/forums...s-2001-c5.html

In the link in post #2, ezgone found the problem by bending the contacts on the jumper comb so certain ones would not contact the wired connector. I was thinking that you might be able to put thin strips of scotch tape on both sides of them to insulate the contact you want to isolate. Just be careful not to deform the mating contact, and be sure to remove the tape when your done.

 

Thanks for the help but that didn't work either. So some how or another, both of my star connector caps came undone. I replaced both and still receive multiple errors on initial accessory location. once in the DIC mode, PCM is still NO COMM but the rest is viewable with several codes. I also noticed the constant door chime with the door open and key out only on the driver side goes away when I disconnect the black connector behind the accordion boot.

 

Have you checked all the voltages for the PCM are at proper levels?

You mentioned that you did extensive engine mods. Check that all the grounds in the engine compartment have been reattached and are clean and tight.

With the black door connector plugged in and star connector 2 removed are you still getting the chime with the key off?
See post #10 in this thread.
https://www.corvetteforum.com/forums...door-open.html

With everything plugged back in, clear the codes then read them again and post them.

 

I have not checked voltage yet. I went back over all the grounds that I would of messed with and removed and cleaned just incase and still no luck.

With the black connector connected, I'm still getting the chime with the Star connector with the four wires disconnected but not when the other one is removed.

Here are all the codes I'm getting with everything hooked up and also with just the four wire cap removed.

PCM - No Comm.
TCS - U1000 H C
BCM - U1255 H C
SDM - U1000 H C, U1016 H C
HVAC - U1160 H
RFA - U1000 H C.

I am able to clear it but they return once the ignition is turned back on.

 

I'm not sure what is going on with the door chime so for Now I would leave the black connector unplugged.

When you unplug star connector 2 you are disconnecting the LDCM, RDCM, and SCM from the serial bus so I don't know why those aren't on your list.
Those module aren't critical and disconnecting star connector 2 did not solve the problem but to simplify things you can leave that unplugged for now.

Star connector 1 is a jumper for all the other modules so when you pull that you will have no comms. to anything. The BCM communicates the door ajar or other faults that sound the chime, via the serial bus to the IPC. That is why the chime stops when star connector 1 is out.

What the Kent Moore tool does is plug into the connectors where you removed the jumper comb and the two rotary switches on the tool allow you to connect a scan tool to the DLC and select individual module to communicate with. If you are careful you can make up some jumpers and do the same thing. Foe example: On Star connector 1, if you put a jumper from A (DLC) to B (PCM) your scan tool should be able to communicate to a working PCM.

The BCM U1255 is tell you that the BCM can't communicate with the PCM or IPC. Because the PCM has no comms at all, it is the likely cause of the problem. The other U codes are telling you that they are having trouble with communications, so they are less likely to be the source of the problem.

If all power and grounds to the PCM are good you need to check the serial data line from the PCM for an open, short to ground, or short to voltage.
I am not an expert on this stuff but 'll try to help if I can.

BTW is you want to buy the correct male pins to make jumpers you can get them from Mouser. part number 829-12077628

 

Any progress? I was think that if your buddy has a bench tuning harness you could pull the pcm and verify that the PCM is good by communicating directly from the PC to the PCM. It is also a safer way program the PCM. The nice thing with the Kent Moore tool is you can isolate the PCM from the other modules when you upload or download to the PCM without removing the PCM.

Not to get off track, but if your buddy wants to make a bench harness, go here. I don't know what the pin out for the HP Tuner cable is so he will need to check that.
http://www.gmtruckcentral.com/articl...h-harness.html

I had a chance to look at the door chime problem. If wire 745 is shorted to ground, the BCM will see a constant door ajar signal. When you unplug the connector you are removing that short and the BCM turns off the chime. Refer to the LDCM schematic

 

Bill Curlee has some good troubleshooting tips in this thread.

https://www.corvetteforum.com/forums...-there-is.html

 

Any progress?