I have the SYS light showing up on the dash, but there are no codes. I did, however, recently install a new stereo (headunit). I am posting a video of my SYS light and scanner readings. Can anyone help? Everything seems to be working fine.

 

If you look in the audio section there is a FAQ and you will find there is a resistor that needs to go in the lighting circuit I beleive if you do not have the C68 AC. It is all about the CCM looking for a load on the lighting circuit from a standard bulb as opposed to the LED stuff. It is a pretty common problem doing a head uit upgrade.

 

Thank you

 

yep I had the same problem when I installed a stereo in my 95.
the resisters go in the dash area where the old stereo was,here is a bad drawing but maybe you can make something of it

 

Here is the info for the resistor fix.

http://www.corvetteforum.net/c4/dave8476/index4.shtml

Sorry I only have the link and not the actual pages.

 

Hey guys!!
I did the resistor fix- 1k ohms 1/2 watt- one to grey/black- one to purple/white- the other end of both resistors to switched power. I disconnected the battery for ten minutes and when I reconnected everything I still got the SYS. What to do now?
I had to disconnect the harness from the receiver under the dash for my new adapter harness. Does the receiver under the dash need that power for the resistor fix to work?

 

Not sure how to respond to this sentence or the receiver needing power for the resistor to work.

I am going to guess that it may not be hooked up correctly. The resistor gets switched power and not having done it I cannot be too sure here if you grabbed the correct power wire, did you measure?

But what really bothers me is that you said you have no codes. According to the information it should set a code if the dimmer light circuit is the problem which is the fix you are trying to make. Perhaps you did a good job and the SYS light is caused by another problem. It's real common if the battery is not in good shape the SYS light does light. Do you think this is possible and how old is your battery?

 

Its possible the battery is low, due to having the doors open and running the radio without having the engine running, but she started right up and I did drive her for about 20 minutes. The battery is only a few months old.
The switched power I used was from the new radio and I made sure it was the right wire from schematics. I soldered all connections and used heat shrink wrap.
I'll try and put the battery on the charger if it checks low.I wish there was a code set, just so I know what to fix.
Thanks for your response

 

Battery is good. 13v when off and 13.9v when running

 

I found this. It says the purple/white wire needs a 10ohm resistor and diode(in series) instead of the 1k 1/2watt resistor used for the grey/black wire.
I guess I'll try that next.
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CCM (Central Control Module) Codes 72 and 74 usually occur after the radio control head was replaced. The radio head LED and LCD open circuits are noticed by the CCM, setting the code. There is a simple fix while the radio head is being replaced. Resistors and one diode must be installed to alleviate the problem. A 1K 1/2 watt resistor is installed in the following manner: one side of the resistor must be powered by the radio head C2 connector in position 8 (pink wire). Connect one end of the resistor to this wire. This will send the correct voltage signal to the CCM once the other side of the resistor is connected. At radio head connector C1, locate the gray/black striped wire at position 3. Connect the other end of the resistor here. Be careful: the radio head has two gray/black striped wires in connector C1. The gray/black striped wire at position 4 is the incandescent lamp control. It will not set a code when left disconnected. To recap: the resistor will be installed at connector C2 position 8 on one end and connector C1 at position 3 for the other end.

LED dimming circuit

The purple/white striped wire at the radio head connector (C1 position 2) requires a 10 Ohm resistor and diode in series with the pink wire. The same pink wire from connector C2 position 8 is used for power. Connect one side of the 10 Ohm resistor to the pink wire. The diode should be installed in series with the resistor. Diodes are an electrical check valve allowing current to flow in one direction only. Diodes have an arrow on their barrel denoting direction of current flow. The arrow should point away from the resistor towards the purple/white striped wire. One side of the diode connects to the resistor. The side with arrow pointing out goes to the purple/white striped wire. This will prevent “SYS” from flashing while you’re enjoying the new sound system.

Module 4 is ECM