When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey y'all. I'm new to the forum and I have a big question for those out there.
My 06 C6 Z06 (only 11k miles) has sat for a year and half without a battery installed. In placing a new fully charged battery in the vehicle and new batteries in the key fobs, I was a little shocked the car wouldn't come to life. Nothing, dead as a door nail and the Fobs did not do a thing for the car. Doors would not open, nothing (luckily, I had hatch physical key). The only real thing noticed was power was to the red outline led of the two door locks and the car horn did its theft alarm function. Other than that, totally dead. Checked power at fuse box under the hood, it had the 12V power coming to it. Some past history: a few times the car would blank out the dash if abruptly shifting or go over a road hump too aggressive. I would have to shut car off, then restart and it would clear. This was more annoyance than anything and chalked it up that I needed to go searching for a loose ground someday.
I have found a great deal of good information on this site and on YouTube to begin a process of troubleshooting starting with inspection, cleaning and tightening grounds and ensuring the relay/fuse insertions are tight, tighten as necessary and then focus on the BCM area for looseness and signs of issues. Then I am going to go looking for open circuits somewhere. But dread that as much as going after the ECM area.
Any other advice for a root cause?
I hate the idea of an ECM connector issue or ECM, but willing to go that far if necessary. Next question, can the various modules in the vehicle (BCM, ECM, etc.) be independently tested by a service tech removed from the vehicle? Thank you all in advance.
Where was the car stored ??…outside or inside ??….if outside maybe some rodent damage…are you sure the new key FOB batteries are good and did you actually check them with a DVOM ??….if the FOB battery is dead and the FOB is functionally OK the car should start when placed in the back up antenna slot in the glovebox…have you tried that ??…since the passive entry and immobilizer functions are inop did you check fuse 11 (ECM/ TCM/EASY KEY) in the under hood fuse box with a 12 volt test light ???…that fuse is “hot at all times” and power comes from the battery…may even be a good idea to check for power and ground at the RCLDR…the key to diagnosing this is knowing you have a known good FOB…you should pick one of these FOB testers from Amazon…only $39.00….I would start there…and BTW there is no way I know of to check these modules once out of the car…you probably can’t get the car in either ACCY or RUN mode to get a scan tool hooked up to check what modules you can and can’t communicate with.
May also be a good idea to check ground G104 which is below the battery tray…if you do remove the RCLDR you can probe pin 5 on the C1 Connector and see if the ground is good by testing with a 12 volt test light connected to B+…you can first since pin 12 on the C1 Connector (J1) on the BCM since it is easily accessible.
Well, this morning the Z06 decided to power up and it did recognize both FOBs. It did not, however, turn the starter motor over. But it tried.
I then tested the car battery, and it was putting out 12.5V and 575Amps. I also confirmed that that the FOB batteries were good, 3.2V (brand new). I am going to go through all grounds and the fuse blocks to clean up corrosion, dirt and tighten up. If I find any fuses or relays that appear stressed by heat or corrosion, I will replace. Then if it still indicates it wants to play with my mind, I will go into other areas.
Background, the car has been held hostage during a divorce. It was garaged the entire time. I have every reason to believe that to be true since it was exactly as I had left it in the garage (I purposely removed the battery prior to going on business trip over a year ago).
Just to rule out the “control” side of the starting system you can jumper out pins 30 and 87 at the crank relay…if the starter cranks the control side of the starting system needs to be diagnosed…when attempting to start do you hear any clicking coming from the starter solenoid ??…after sitting for that long you may want to give the starter a few “love taps”…but not to hard….just be 100% sure you are jumping the right fuse box terminals.
FYI, pin 30 is the terminal closest to the engine and to the windshield…87 is always caddy corner so it would be closest to the fender and to the front of the engine.
Yes, the starter clicks as if to try to turn. I did just find a generous amount of oxidation at the main battery ground point to the aluminum frame (G303). I am going to clean it and the lug up well, reattach and coat it with an oxidation inhibitor. I'm also considering clearing some of the black epoxy paint at the attach point too.
But curious if GM engineering left it that way for a reason. Didn't do such things that I recall in the aircraft business.
To see if you have a bad block ground is take a 12 volt test light connected to battery negative…probe the frame rail with the test light…try to start the car and if the test light illuminates you have a bad block ground…if you have a heavy jumper cable connect it to battery negative and a clean spot on the frame rail…see if the car now cranks !!
Update: All grounds cleaned and sealed. Battery terminals replaced with more secure retention terminals. Next, I secured the most forward harness to the fuse/relay box in the engine compartment. I saw in a YouTube video where someone had posted on his Z06 that GM had done a recall in the earlier models and didn't properly secure this harness in the process causing the loose harness to pull on the terminals to the relays on that forward block. I had noted mine had his exact same issue, so secured it properly and inspected all fuse/relay blocks for issue.
So now I am happy to report, the Z06 is running just fine now. Starts better than ever and no gremlins.
C6 Z06 Electrical
