2004 Chevy Express 3500 – 6.0L LQ4

Knock Sensor Circuit Issue (No Power at Harness Connector)



Background:

For several years I intermittently received a Knock Sensor 2 Low Circuit code. After clearing, it would often stay away for days, weeks, or even months.



Recent Repairs:

• Installed new AC Delco knock sensors (both)
• Installed new Ac delco knock sensor sub-harness

After completing the work, the engine idled perfectly with no codes. Once I reassembled everything (doghouse, seat, dash panels) and took the van for a test drive, the fault returned—this time for both knock sensors.



Current Issue:

Upon further inspection, I discovered there is no power at the main harness connector feeding the knock sensor sub-harness.



Request:

I’m looking for a detailed wiring diagram for the knock sensor circuit on a 2004 Chevy Express 3500 (6.0L LQ4). Specifically:

• Power and ground sources
• PCM pinouts related to both knock sensors
• Any known failure points (connectors, splices, or grounds) common to this circuit

Any guidance, diagrams, or diagnostic tips would be greatly appreciated

 

https://charm.li/Chevrolet/2004/Expr...20Diagram%206/

Try this.