2005 5.3 1500 Silverado no crank

[Blaise]

My 2005 will not turn over, have checked all fuses and relays. Engine will crank and run if I jump starter relay pin #30 to #87. My crank fuse shows power when key is in start position. I am not seeing a ground at #86 or 12 volts at #85 at start position of the relay. From what I see in schematics it seems to point to PCM issue. One other thing I noticed is seat belt indicator is very dim in cluster and the tach will read zero when I turn fog lights on. I have gone through grounds under driver side of cab and at engine and grill. Any ideas?

[Jsdirt]

Is the cluster responding normally to key inputs? Just want to rule out a faulty key switch first. If there's no change in the cluster from run to start, there's a switch problem.

 

If that checks out good, try jiggling the shifter, or try starting it in neutral - if that doesn't work, try holding it towards one gear or the next while cranking - if any of this results in a crank, you've got a failing neutral safety switch, or it needs adjustment. Scan tool should show neutral or park when either is selected.

 

If all this checks out good, the next test would be the wiring from the fuse box to the BCM - which ever wire is supposed to supply power, or ground to the primary side of the relay.

[Doug_Scott]

You may want to try swapping the relay with one of the other ones in the fuse panal.  The relays tend to be interchangeable, as long as they physically fit.  I would first rule that out. I know you have tried bypassing it and the truck starts, that leads me to try swapping the relay first before movie on with diagnosis. 

[Blaise]

1 hour ago, Doug_Scott said:

You may want to try swapping the relay with one of the other ones in the fuse panal.  The relays tend to be interchangeable, as long as they physically fit.  I would first rule that out. I know you have tried bypassing it and the truck starts, that leads me to try swapping the relay first before movie on with diagnosis. 

 

[Blaise]

Went to test wires and when I unplugged the PCM found a lot of corrosion and pins that had corroded away. Seal was allowing salt and water in . Going to salvage yard to find replacement harness if possible 

[Jsdirt]

Good find!  Another common issue here in the Northeast as well.  

[Blaise]

On 4/27/2019 at 7:27 PM, Blaise said:

Went to test wires and when I unplugged the PCM found a lot of corrosion and pins that had corroded away. Seal was allowing salt and water in . Going to salvage yard to find replacement harness if possible 

Truck has run good for a week, then all of a sudden shut down going down the road, tried it a couple times then started and ran fine. Am I still dealing with a wiring issue or could it be PCM?

[riverbanks]

Are you able to start it by key all the time now? harness repaired at pcm?