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Home >> GMC >> 2018 >> Terrain Denali, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 7 (Engine Controls And Fuel - 1.5L (LYX) - Diagnostic Information And Procedures (P0351 - P26C8) And Symptoms) >> Diagnostic Information And Procedures >> DTC P0685, P0686, P0687, P0689, P0690, Or P1682: Engine Controls Ignition Relay Control Circuit >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition/Vehicle - Off
  2. Remove the component:KR75 Engine Controls Ignition Relay
  3. Verify a test lamp turns On between the test points:
    • B+ circuit terminal 3 & Ground
    • B+ circuit terminal 1 & Ground
    • If the test lamp does not turn On 

      Replace the component:X50A Fuse Block - Underhood

    • Go to next step: If the test lamp turns On 
  4. Ignition - On / Vehicle - In Service Mode
  5. Connect a test lamp between the test points:Control circuit terminal 2 & B+ circuit
  6. Perform the scan tool control function:Engine Controls Ignition Relay - On and Off

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector:X1 @ K20 Engine Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1 V between the test points: Control circuit terminal 2 @ Relay Socket & Terminal 67 @ Control module harness
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points:Control circuit terminal 2 @Relay Socket & Terminal 67 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component:K20 Engine Control Module
    • If the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector:X1 @ K20 Engine Control Module
    3. Test for infinite resistance between the test points:Control circuit terminal 2 @ Relay Socket & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component:K20 Engine Control Module
    • Go to next step: If the test lamp turns On and Off 
  7. Verify the fuse is not open:
    • F14UA Fuse
    • F20UA Fuse
    • If the fuse is open 
    1. Ignition/Vehicle - Off
    2. Disconnect the electrical connector: X1 @ K20 Engine Control Module
    3. Test for infinite resistance between the test points:Output terminal @ F20UA Fuse & Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance - Replace the component: K20 Engine Control Module
  8. Disconnect the electrical connector: X3 @ K20 Engine Control Module
  9. Test for infinite resistance between the test points:Output terminal @ F14UAFuse & Ground
    • If less than infinite resistance - Repair the short to ground on the circuit.
    • If infinite resistance - Replace the component: K20 Engine Control Module
    • Go to next step: If the fuse is not open 
  10. Ignition - On / Vehicle - In Service Mode
  11. Verify a test lamp does not turn On between the test points:Control circuit terminal 2 & Ground
    • Go to next step: If the test lamp turns On 
  12. Disconnect the electrical connector: X1 & X3 @ K20 Engine Control Module
  13. Test for less than 1 V between the test points:
    • Control circuit terminal 73 @ Control module harness & Ground
    • Control circuit terminal 16 @ 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 
    • Go to next step: If the test lamp does not turn On 
  14. Ignition/Vehicle - Off
  15. Connect a 30 A fused jumper wire between the test points:Control circuit terminal 5 & B+ circuit terminal 3
  16. Ignition - On / Vehicle - In Service Mode
  17. Verify the scan tool parameter:Engine Controls Ignition Relay Feedback Signal = Within 1 V of the battery voltage
    • If not within 1 V of the battery voltage 
    1. Ignition/Vehicle - Off & Remove - Jumper wire(s)
    2. Disconnect the electrical connector: X1 & X3 @ K20 Engine Control Module
    3. Test for less than 2 ohms between the test points:
      • Control circuit terminal 5 @Relay Socket & Control circuit terminal 73 @ Control module harness
      • Control circuit terminal 5 @Relay Socket & Control circuit terminal 16 @ Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K20 Engine Control Module
    • Go to next step: If within 1 V of the battery voltage 
  18. Test or replace the component:KR75 Engine Controls Ignition Relay
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