Circuit/System Testing

Test 1

NOTE:

It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

1. Ignition/Vehicle & All vehicle systems - Off
2. Disconnect the electrical connector: X1@K20 Engine Control Module
3. Ignition - On/Vehicle - In Service Mode
4. Momentarily connect a 3 A fused jumper wire between the test points: Control circuit terminal 64 & B+

   Verify a click cannot be heard or felt at the component when connecting and disconnecting the jumper wire: X50A Engine Wiring Harness Junction Block

   • If a click can be heard or felt 

     Replace the component: K20 Engine Control Module

   • Go to next step: If a click cannot be heard or felt 
5. Ignition/Vehicle - Off & Remove - Jumper wire(s)
6. Remove the component: X50A Engine Wiring Harness Junction Block
7. Test for less than 10 ohms between the test points: Ground circuit terminal A4 X1@Fuse/Junction Block Harness & Ground
   • If 10 ohms or greater 
   1. Disconnect the ground connection:
      • {Silverado/Sierra} G104
      • {Escalade/Suburban/Tahoe/Yukon} G102A
   2. Test for less than 2 ohms between the test points: Ground circuit terminal A4 X1@Fuse/Junction Block Harness & The other end of the circuit@Ground terminal
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Repair the open/high resistance in the ground connection.
   • Go to next step: If less than 10 ohms 
8. Ignition - On/Vehicle - In Service Mode
9. Test for less than 1 V between the test points: Control circuit terminal 64@Control module harness & Ground
   • If 1 V or greater 

     Repair the short to voltage on the circuit.

   • Go to next step: If less than 1 V 
10. Ignition/Vehicle - Off
11. Test for infinite resistance between the test points: Control circuit terminal 64@Control module harness & Ground
    • If less than infinite resistance 

      Repair the short to ground on the circuit.

    • Go to next step: If infinite resistance 
12. Test for less than 2 ohms between the test points: Control circuit terminal 64@Control module harness & Terminal C5 X3@Fuse/Junction Block Harness
    • If 2 ohms or greater 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 ohms 
13. Test or replace the component: X50A Engine Wiring Harness Junction Block

Test 2

1. Ignition/Vehicle & All vehicle systems - Off
2. Remove the component: F60UA Fuse & F80UA Fuse @X50A Engine Wiring Harness Junction Block
3. Connect a test lamp between the test points: Input terminal@F80UA Fuse & Ground
4. Ignition - On/Vehicle - In Service Mode
5. Perform the scan tool control function: Sensor Supply Voltage - On and Off

   Verify the test lamp turns On and Off.

   • If the test lamp does not turn On and Off 

     Test or replace the component: X50A Engine Wiring Harness Junction Block

   • Go to next step: If the test lamp turns On and Off 
6. Verify a test lamp does not turn On between the test points:
   • Output terminal@F80UA Fuse & Ground
   • Output terminal@F60UA Fuse & Ground
   • If the test lamp turns On 

     Repair the short to voltage on the circuit.

   • Go to next step: If the test lamp does not turn On 
7. Replace the component: K20 Engine Control Module