Hello All: I am new to the forum and the reason that I have not joined before even though I have owned Corvettes for 20 years is that I usually just take the vehicle to the dealership. However, I am getting rather tired of the lack of experience that I am witnessing at my dealership. There have been many times that they do not know what the problem is and suggest changing a part, only to find that it did not cure the problem and I'm the one who is out of pocket. I have a 2002 Z06 with 20K miles on it that I've owned since new. I currently have a starting problem (intermittent) that went into the dealership to be repaired. Again, they do not know what the cause is and the repair that they did was a work around. The Tech disconnected the battery and joined the +VE & -VE cables (Global Reset), reconnected terminals to battery and vehicle started up. I complained and said that this was not a fix and all that they were doing was masking the problem. The Tech's response was that because it was an intermittent problem, he probably wouldn't be able to find the issue. Keep an 8mm wrench handy and if it doesn't start I could do what he just did....Hmm

So, here I am hoping I might find a solution on this forum. I did read the sticky "Important Electrical Information" by Bill Curlee and thought that it made sense to start there. So I disconnected/unplugged 2 of the grounding connectors in the engine bay, the one that Bill showed pictures of and the one by the coolant reservoir. They were both clean with no corrosion. Went to start vehicle and nada...The low fuel warning, ABS, Reduced Power etc flashing in front of me. I decided to just disconnect the -VE terminal from the battery and then reconnect. The vehicle started up. So no Global Reset required as the Tech suggested. This allowed me to get the DIC codes and here they are: 28 TCS U1000 H - 58 SDM U1000 HC + U1064 HC - 60 IPC U1160 HC + U1176 HC - A0 LDCM U1064 H - A1 RDCM U1064 H - Also when the diagnostics was cycling through it registered BCM No Comm and HVAC No Comm. I'm leaning toward the BCM, but I have no real basis to confidently say that's what it is.

It would be great to hear any suggestions you may have.

Thanks!

 

When the problem occurs, is it a long, slow crank, or no crank at all? And when it works, is it a fast crank with immediate start?

If you have a voltmeter, check the voltage on the battery terminal screws..
If low, disconnect the battery and check voltage on the battery proper.

if the battery cables ends are dirty or corroded, get a dremel/wire brush and clean them.
Both sides. (You'll have to remove the terminal posts to clean both sides of he cable end.)
.
While you have the posts out, inspect them.
If they are stripped, corroded, rusted, or even appear to be, replace them (about 2.50 @ Advance auto)

Making this particular suggestion because in the last couple months, both my C5 and my GFs Buick had start and/or charging issues.
The C5 battery post had stripped threads, so intermittent contact and poor power transfer.
The Buick had corrosion in the base of the terminal screw, which preventing power transfer. (meter on the screws read zero, meter on the battery proper, 14.)
Replacing the terminal posts has resolved the issue on both vehicles.

Might also want to pull the panel from the front passenger footwell and verify no moisture around the connectors for the computer you'll find when the panel is removed. (if the A/C drain is plugged, it'll drip in that area - if the computers connectors get wet, it causes all sorts of weird electrical behavior)

 

Please clarify what no start problem means, does the starter crank but engine does not fire, or does the starter not turn the engine over. If the starter fails to turn the engine over one of the most common causes of intermittent starting is the starter solenoid which can be checked by measuring between ground and the purple switch wire on the solenoid for 12v when the key is turned to the start position, 12volts present and the starter fails to crank means the solenoid is at fault. If 12 volts is not present when key is turned to start means the theft deterrent relay 'TDR" is bad or not being energized because of bad contacts in the ignition switch contact block, bad contacts that read the resistor chip in the key, or a problem with the clutch safety switch.

 

Hi aj98 - Thanks for the response. First, I need to clarify that the vehicle does not crank, my bad. It's dead when I turn the key. As a side note, I have performed the tasks you've outlined. I have even replaced the battery. Terminals have no corrosion and look good. The post threads are not stripped. There is no moisture that I can detect in the front passenger footwell. It is an intermittent fault and this morning I went out to try some more tests and it fired up without me doing anything. I have to wait now until it does not start again so I can proceed with other data serial tests.

 

The messages and U series DTCs are leaning towards a SERIAL DATA BUSS ISSUE. I also have an 02 ZO6 that I purchased brand new. Out of the clear blue, had the same issues many years ago. Same DTCs messages and grief!

See if you also loose the ability to operate the door locks and windows with the drivers or passengers door switches.

Turned out to be an issue with the door wiring harness electrical connector/s.

The very next time it happens, open the drivers door and look at the rubber boot that connects the door to the door frame. If you pinch the boot, you will feel a wire harness inside. Pinch the harness and shake the hell out of it. Turn the car on and off and see if it resolves the issue.

There are two electrical connectors that live inside the door A pillar (where the boot connects to the body) Pop out the boot and fish out the connectors. The connector with the SIX wires is the door power plug. The FEMALE PINS inside the six pin connector can and will spread apart over time (heat and vibrations) and loose positive contact with the male pins. This causes the module to turn on and off rapidly and corrupt the serial data buss. (thus the NO COMMS issues)

The drivers seat connector plug can also cause the same issues if it gets damaged or wet.

Bill

 

Hi mmartinez - Apologies for not being more specific. It does not crank at all. Totally dead with all the spurious error warnings that pop up like traction control, ABS, low fuel, reduced power and so on. Also, horn does not work, door locks do not work, radio does not work. Haven't checked everything yet, but that's what I know so far. Unfortunately, I went to start more testing this morning and the car fired up straight away....Go figure!

 

Thanks for the suggestion Bill. I actually found one of your earlier posts this morning describing exactly what you suggest and that is going to be my next step the next time the vehicle does not start. I will report back my findings at the next opportunity.

 

I'm on the same page as Bill Curlee since you mention all the crazy messages on the dash. It is worth the 15 minutes to check the connectors between the chassis and door. Remove the accordion at the chassis side and pull the wires out from the chassis. You will find the connectors Bill is referencing.

 

LOL!! When my door connector acts up, the engine will crank but not fire. I also get all the screwey gages and messages. I can crank it all day but the engine will not run. As soon as I open the drivers door, shake the rubber accordion tube, turn the ignition OFF and back on, EVERYTHING is back to normal (until the next time there is a poor connection in that connector. Some C5 have the messages and gage issues but the car will crank and run fine. All depends on which BIT in the electron bucket has a hair crossed it butt.

NOTE,, I have since FIXE the issue and have NOT had any more issues with it. BUT, it's only time before the connector female pins spread apart again.

The Wheel Speed connectors will do the exact same thing and cause a WSS speed issue. YES SIR!!

 

Detail behind the basis for my suggestion:

that's what mine was doing.
Worked as expected one day, slow nor no crank the next...no power, no electrical anything.
Random reappearance of the same behavior.

Jiggled around both cables. Felt tight, but when positive was jiggled at the battery connector, I heard everything energize. let go, click.
Walk around to the drivers door, insert key, nothing. not even a door chime. Back to the cable, jiggle, energize sounds. click.

It wasn't until I pulled the battery to get it out of the way to clean the cables ends that I noticed many of the threads were flattened instead of sharp edged. Cleaned everything, reinstalled the battery, same behavior.

So my warped logic went ...hmmm....flattened threads, less metal-metal contact....slightly looser fit...possibly less efficient power transfer.
2.50 is certainly cheaper than having it flatbedded to the dealer....
Replaced the terminals, tightened up, haven't had a problem since.

GFs car had no crank, no lights, no electrical anything, no crank, even with jumper cables.
Meter read 0 on the terminals and 14 when I disconnected both cables and stuck the probes directly on the battery.
Replaced the terminals, tightened up, started right up. No further issues

 

Ok Bill - I went back and the vehicle was dead again, so I was able to test. So, I tried the the jiggling of the wires in the accordion boot while trying to start the vehicle, still nothing. Pulled boot out the door and frame so I could get to the connector. Jiggled that aggressively while trying to start and still nothing. So I went on to try your other suggested methods. First, pulling the shorting link off the Star connector 2. Tried starting again and still nothing. Next pulling the shorting link off Star connector 1 and connecting a jumper link between B & M. Tried Starting again and still nothing. Disconnected the BCM to see what the pins looked liked. All good no corrosion and none bent. Connected the the Star connectors back up and then connected the BCM back up. As I plugged the middle connector into the BCM the alarm (horn) started going off. I knew then that it would start back up as the horn is disabled when the non starting condition is present. Sure enough, put key in and it fired up.

Here's what I have observed thus far. When the vehicle is running ok and starting up I have noticed the following:
1. When you insert the key and then pull the key back out you here a click in the passenger foot well and a sound from the door I believe (not sure if it is the door or the steering wheel area). When the vehicle does not start I do not not hear those sounds.
2. Again when the vehicle is starting ok and you turn the key to the first position (not starting the vehicle) I hear an even louder clicking sounds (not continuous) from the passenger foot well. When you take the key out of the ignition switch the clicks happen again as well as the sound from the door/steering wheel area. When the vehicle is not able to start, I do not hear any of those sounds.
3. When the vehicle is able to start and the door is open, the security light flashes on the dashboard as it should. This does not happen when the vehicle is unable to start.

Any other ideas?

 

There is a specific BCM issue where the BCM does not properly shut down and does not properly come out of the sleep mode. Its a well known issue that does not happen very often but it has happened to several forum members. I have a saved post that details the exact subject BUT since the fine folks at the forum management changed the forum post format, I can no longer just cut and paste the link.

PM me an e-mail address and I will send you the info.

Bill

 

Sent you a PM Bill. Thanks!

 

Thanks 8VETTE7 - This info along with the link Bill sent me via PM sure is suggesting a BCM that does not wake up unless it is reset.

 

Got the link Bill - Thanks. I'm thinking it's a BCM that is not waking up. I will locate one and report back when I receive and install it.