2003 GMC Sierra - Random "No Start"

Maintenance/Repairs
1

I own a 2003 Sierra 1500 SLT Extended (4-Door) Cab which I bought brand new. It currently has 120k+/- miles on it, but the problem I’m about to describe started about 5 years ago. Here’s the issue: Whenever I first attempt to start my truck, I know the odds are 50/50 that it will actually start. When I turn the key, it will either crank right up like it’s brand new or it will do nothing at all–no cranks, no clicks, just complete silence. When the weather is colder, the chances it will start are slightly better. Those chances go downhill as the weather improves–the frequency of “non-starts” increases. I have had a whole lot of mechanics–both physical and virtual–try to diagnose this problem. I even left my truck at a GMC dealership for 4 days so they could replicate the problem and diagnose it. Unfortunately, my truck started on every attempt they made which was 2 or 3 times per day. The only hint of where the problem my lie came from an automotive electronics technician. He said he can’t be sure unless he replicates the scenario, but he said the factory installed alarm system is most likely the cause.

Any ideas out there?

2

If nobody’s done it, have the positive battery cable assembly replaced.

You’re vehicle has the side mount battery cables. And the positive connection is prone to unseen corrosion causing the starting problems you describe.

Afterall, you’re vehicle is ten years old.

Tester

3

@bernjoel

Passlock sensor

http://dormanproducts.com/p-48286-924-713.aspx?year=2003&make=GMC&model=Sierra%201500&parttype=Ignition%20Lock%20Housing

4

I would gamble on the starter relay.

5

Try this. The next time the truck fails to start…shift to neutral and see if it starts. If it does then you have a bad neutral safety switch. They tend to fail in an intermittent manner. It may not be the problem but it’s a simple test and all the boxes have to be checked off before the real problem is ever found.