Circuit/System Testing

Engine Control Module

1. Ignition OFF, disconnect the harness connectors at the K20 ECM.
2. Ignition OFF, and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 Ω between the ground circuit terminals listed below and ground:
   • Terminal 1 X2 (LLT)
   • Terminal 2 X2 (LLT)
   • Terminal 4 X2 (LLT)
   • Terminal 73 X1 (L99, LS3)
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Connect a 15 A fused jumper wire between B+ and the KR75 powertrain relay switch control terminal 87. Ignition ON, verify that a test lamp illuminates between the IGN/B+ circuit terminals listed below and ground:
   • Terminal 56 X2 (LLT)
   • Terminal 54 X2 (LLT)
   • Terminal 3 X2 (LLT)
   • Terminal 5 X2 (LLT)
   • Terminal 6 X2 (LLT)
   • Terminal 41 X2 (LLT)
   • Terminal 20 X1 (L99, LS3)
   • Terminal 19 X1 (L99, LS3)
   • Terminal 47 X1 (L99, LS3)
   • Terminal 18 X1 (L99, LS3)
   • If the test lamp does not illuminate, test the IGN/B+ circuit for a short to ground or an open/high resistance.
4. If all circuits test normal, replace the K20 ECM.

Fuel Pump Control Module

1. Ignition OFF, disconnect the harness connectors at the K27 fuel pump control module.
2. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 Ω between the ground circuit terminal 25 and ground.
   • If greater than the specified range, test the ground circuit for an open/high resistance.
3. Verify that a test lamp illuminates between the IGN/B+ circuit terminals listed below and ground:
   • Terminal 21
   • Terminal 1
   • Terminal 8
   • If the test lamp does not illuminate, test the IGN/B+ circuit for a short to ground or an open/high resistance.
4. If all circuits test normal, replace the K27 fuel pump control module.