Last night when I went to go to work, my car was totally dead, no lights on the dash or anything. I checked the battery cables and my positive cable was a little loose because I removed the connector I had installed that went back to my audio amps, and the stud was too long to cinch the cable down tight.

I got the cable tight and drove to work, about 3 miles from my house. Part way there I hit a little bump in the road and the door chimes starting gonging on me (they have never worked since I bought the car either). They stayed on until I got to work and I shut the car off.

When I went to come home, my car would not start, but I had power. I checked and my CCU fuse was blown.

I have the FSM but there are two 32 pin connectors going into the CCU, and it's really hard to get to the CCU. I actually happened to have most of the dash apart because I have been working on restoring the interior a bit, so I plugged my multi-meter into the CCU fuse socket and turned the key on, and then I started unplugging every single connection I could find on the wiring harness under the dash while watching the voltage on the multimeter. I was thinking when I unplugged the wire that is shorting to ground, the voltage would drop on my multimeter.

But the voltage never dropped.

Since I had the FSM I tried to bypass the CCU's control of starting the car by manually enabling the starter enable relay so it would crank, and I grounded the dark-blue wire coming out of my ECU that goes to the CCU (in my FSM it shows that the CCU grounds that wire to enable the fuel pump relay).

So the car cranks and I can feel the fuel pump relay engaging, but the thing won't start. I have not tried pulling a plug wire to see if I have spark or loosening a fuel hose to see if I have fuel yet.

Anyone have any ideas on what could be causing my CCU fuse to blow? I am guessing that at this point I need to get to the CCU. so I could start checking the wires that go straight into the CCU for shorts.

I have a sinking feeling that the CCU went bad. I would like to get the car home though and I am wondering what else I need to do to get the car started.

 

Ok, I just read here: http://www.joestradingpost.com/vats/89_fuelenable.htm

That the dark blue wire I grounded to enable the fuel signal is actually supposed to be a 5v 30hz signal.

I will make a quick circuit to emulate that signal so I can try and get the car home. I'm really wondering how to figure out if my CCU is bad, or if it's some wire running into the CCU that is shorting and causing problems.

 

I'd quit jumping HOT wires and avoid any further damage...!

Control modules, ECMs, PCMs rarely fail. 99% of the time its grounds or power source connections . Harness or connector issues.

Go to the battery area and look for the power source connections that are likely on fusable link. They are listed in the FSM as "always ON" circuits or HOT always circuits for main control functions that use control grounds for mngt.

Next look at all the harness grounds that are relevant. The most critical is the G104 bundle near the oil filter on the block or bellhousing.

Corvettes are plastic and plastic provides a damn poor earth plane for grounding. So...there have to be local points of contact as often as possible for all the various systems at the closest possible grounding point. They are everywhere. Sometimes several stacked on top of one bolt. The block has a strap that runs to the frame. The battery has a cable that runs to the frame...
many folks add cables from battery to block, to frame,. utilize brake lines, whatever is metal and common to the whole car. It makes a difference.
Poor contact at the power source origin WILL result in mediocre performance or misfires, poor economy and sluggishness due to the increased resistence from the bad connections. Since the engine controls utilize reference voltage as you know, that signal can be reduced via poor connections just as variable resistence circuits that transmit sensor data TO the ECM can send false signals from increased resistence from dirty/loose or corroded connections.
Your FSM will have a flow chart on how to trouble shoot a CCM fuse thats blowing. I'd follow that to its conclusion.



First rule of Corvette electrical diagnosis...

check all the grounds. Next, move on to source connections and harness connections, splices and general harness health (insulation, wrap etc)

Good luck.
electrical can be both fun and entertaining. If you keep telling yourself that long enough you will eventually come to believe it..!

 

The CCM 10 amp fuse provides 12 volts for the following items
via a White/Black colored wire.

1) Low Pressure Tire Module if you have that option.
2) RH and LH sun visor vanity mirror lamps. Turned on by a switch
on the sun visor.
3) Rear view mirror Map lamp turned on by a switch on the
rear view mirror.
4) 12 volts for the Ignition 1 input to the CCM. It's a White/Black
wire going to the White colored connector of the CCM.

 

Well, I got my car home. I built a little circuit board that injects a 30hz signal into that dark blue wire and that allowed me to start it and get it home with no CCU.

I saw the wht/blk wires, one to the CCU and 3 or 4 that went behind the a-pillar to the rear view mirror and sunvisors. I am planning on unplugging the connectors that run into the CCU and seeing if there is still a short. If so then I have eliminated it being internal to the CCU. I'm hoping it's up in the rear view mirror or visors.