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Home >> Chevrolet >> 2020 >> Impala Premier >> Repair and Diagnosis >> Electrical >> Charging Systems >> Battery, Starting System And Charging System >> Diagnostic Information and Procedures >> DTC P2505 >> Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the KR27 Starter Relay.
  2. Verify a test lamp illuminates between the B+ circuit terminal 3 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is good and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance,
    3. Disconnect the X1 harness connector at the M64 Starter Motor.
    4. Test for infinite resistance between the control circuit terminal 3 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the M64 Starter Motor.
    • Go to next step: If the test lamp illuminates 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the ignition circuit terminal 2 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF, remove the test lamp.
    2. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, refer to Power Mode Mismatch
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF, remove the test lamp.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance,
    3. Connect the KR27 Starter Relay.
    4. Verify the fuse does not open when connecting or working the KR27 Starter Relay.
      • If the fuse opens, replace the KR27 Starter Relay
      • Go to next step: If the fuse is OK
    5. All OK
    • Go to next step: If the test lamp illuminates 
  5. Connect a test lamp between the control circuit terminal 1 and the ignition circuit terminal 2.
    NOTE:

    If the Starter Relay command is not available in the scan tool, verify the test lamps turns on and off when cycling the ignition between the OFF and CRANK position with the parking brake set and clutch pedal pressed (manual transmission) or the transmission in park (automatic transmission).

  6. Verify the test lamp turns ON and OFF when commanding the Starter Relay ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module and disconnect the harness connector at the T19 Power Supply Transformer, Ignition ON.
    2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • Go to next step: If less than 1 V
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module and disconnect the harness connector at the T19 Power Supply Transformer, Ignition ON.
    2. Test for infinite resistance between the control circuit and ground
    • If less than infinite resistance, repair the short to ground on the circuit
    • Go to next step: If infinite resistance
  7. Reconnect the K20 Engine Control Module
  8. Test for infinite resistance between control circuit and ground.
    • If less than infinite resistance, replace the K20 Engine Control Module.
    • If infinite resistance, replace the T19 Power Supply Transformer
    • Go to next step: If the test lamp turns ON and OFF 
  9. Ignition ON, connect a 30 A fused jumper wire between the B+ circuit terminal 5 and the control circuit terminal 3.
  10. Verify the M64 Starter Motor is activated.
    • If the M64 Starter Motor does not activate 
    1. Ignition OFF, disconnect the harness connector at the M64 Starter Motor.
    2. Test for infinite resistance between the control circuit terminal X1 A or X1 1 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • Go to next step: If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the M64 Starter Motor.
    • Go to next step: If the M64 Starter Motor activates 
  11. Test or replace the KR27 Starter Relay.
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