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Home >> Chevrolet >> 2021 >> Blazer RS, FWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls And Fuel - 2.5L (LCV) - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> DTC P0685-P0687, P0689, P0690, P1682, P16A7, P16AF, or P16B3 >> 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 30 & Ground
    • B+ circuit terminal 86 & 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: B+ circuit terminal 86 & Control circuit terminal 85
  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 appropriate electrical connector: 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 85 @ Relay Socket & Ground
      • If 1 V or greater - Repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    5. Ignition/Vehicle - Off
    6. Test for less than 2 ohms between the test points: Control circuit terminal 85 @ Relay Socket & The other end of the circuit @ 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 appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: Control circuit terminal 85 @ 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: F65UA, F66UA Fuse - For the circuit that set the DTC.
    • If the fuse is open 
    1. Ignition/Vehicle & All vehicle systems - Off
    2. Disconnect the appropriate electrical connector: K20 Engine Control Module
    3. Test for infinite resistance between the test points: Output terminal @ 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
    • Go to next step: If the fuse is not open 
  8. Ignition - On / Vehicle - In Service Mode
  9. Verify a test lamp does not turn On between the test points: Ignition circuit terminal 87 @ Relay Socket & Ground
    • Go to next step: If the test lamp turns On 
  10. Ignition/Vehicle & All vehicle systems - Off
  11. Disconnect the appropriate electrical connector: K20 Engine Control Module
  12. Test for less than 1 V between the test points: Ignition circuit terminal 16 X1, 73 X1 @ Control module harness & Ground
    • If 1 V or greater - Repair the short to voltage on the circuit.
    • Go to next step: If the test lamp does not turn On 
  13. Ignition/Vehicle - Off
    14. CAUTION:

    Complete the testing as quickly as possible in order to prevent overheating and damaging the component.

  15. Connect a 30 A fused jumper wire between the test points: Ignition circuit terminal 87 & B+ circuit terminal 30
  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 appropriate electrical connector: K20 Engine Control Module
    3. Test for less than 2 ohms between the test points: Ignition circuit terminal 87 @ Relay Socket & Ignition circuit terminal 16 X1, 73 X1 @ 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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