I have a 2007 Chevy Avalanche LTZ 5.3l 4x4 with 128,000 miles which I purchased used about 8 years ago. Last winter I tried starting the truck after it had sat for some time and all it did was click at the starter. I estimated the aftermarket battery was about 4 years old. I purchased and installed a new battery and the truck started no problem. About a week later I went to start the truck and just got a click at the starter. I tried boosting the truck, but it wouldn't start. I presumed the battery was faulty and returned it to the Retailer who tested it and said it was fine although slightly discharged so I insisted they give me a new battery which they did. I installed the new battery and tried starting the truck again. All it did was click. After turning the ignition on and off about 20 times the truck miraculously started and was fine for another week. Then it happened again so I had the starter removed and tested, found it to be defective and had a new starter installed. The truck started fine up until this January 2020. I started it with the remote starter and used it for some errands. Later in the day I went to start the truck and all that happened was the dash lights and headlights would turn on, but the starter wouldn't crank. After trying several suggestions such as locking and unlocking the doors, trying to start in neutral, trying with brake on, switching the starter relay, nothing worked. I tested all the fuses with a test light and found they were all OK. I then inserted the key into the ignition and just as I turned it to the accessory position the truck started! I turned it on and off several times and also with the remote starter and it started fine. The next morning I went to start the truck and it would not start again!
I used my OBDII code reader and no trouble codes were shown. I used my multimeter and found proper voltage was running to the fuse box. I tried jumping a battery cable from the negative battery post to the engine block and turning on the ignition without success. I disconnected the positive battery cable and left it disconnected overnight. After reconnecting the positive battery cable the next day the truck would still not start. I decided it was time to take it to my local independent garage who has a knowledgeable automotive electric technician. To start the truck I wrapped a jumper wire around the top left prong of the starter relay, reinserted the relay into the fuse block, turned the ignition to the start position and touched the other end of the jumper wire momentarily to the positive post on the left side of the fuse block and the starter turned over and the the truck started! I pulled out the starter relay, removed the jumper wire and reinstalled the starter relay. I drove the truck to my independent garage, shut off the engine and started it up again a few times without any problem.
I advised the technician of the problems I was experiencing and noted that in the last year the truck had a new battery, new starter, new spark plugs & wires, a new ground wire from the drivers side firewall to the engine block at the alternator (as recommended by other GM truck owners) and a new oil pressure sensor installed (located at back of engine close to firewall and very difficult to replace). The technician diagnosed the electrical problem and found there was a very poor ground running to the bottom left prong of the starter relay. He said there was an internal fault with the electronics in the fuse block which could not be repaired and would require a new fuse block at a cost of over $600 CAD from General Motors. To circumvent the no crank problem he ran a negative jumper wire from the bottom left prong of the starter relay to the ground location on the engine block at the alternator. This has remedied the situation until I can find a suitable replacement fuse block.
It appears there are numerous GM truck owners who are experiencing this dreadful and most inconvenient intermittent no crank no start problem and that there are possibly thousands of these defective fuse blocks that could leave individuals stranded in severe climate circumstances with no means of returning from a trip safely. Perhaps General Motors and the NTSB (National Transportation Safety Board) need to investigate this very serious and potentially life threatening safety defect.
Check out this YouTube video which explains problems with the faulty fuse blocks and how to replace them.
https://m.youtube.com/watch?v=25gYezR_k6c