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Home >> Cadillac >> 2017 >> CT6 Plug-In >> Repair and Diagnosis >> Electrical >> Body Electrical >> Hybrid/EV System Controls >> Diagnostic Information and Procedures >> DTC P181C-P181F, P183A-P183F, P184A or P184B: Internal Mode Switch Circuit >> Circuit/System Testing
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Circuit/System Testing

  1. Vehicle OFF, disconnect the X175 20-way harness connector at the transmission. Additional DTCs may set.
  2. Test for less than 2 Ω between the low reference circuit terminal 14 and ground.
    • If 2 Ω or greater 
    1. Disconnect the X1 harness connector at the T6 Power Inverter Module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the T6 Power Inverter Module.
    • If less than 2 Ω 
  3. Vehicle ON.
  4. Verify each scan tool hybrid powertrain control module parameter, Internal Mode Switch 2 - D1/D2/R1/R2/S, displays HIGH.
    • If any parameter displays LOW 
    1. Vehicle OFF.
    2. Disconnect the X1 harness connector at the T6 Power Inverter Module.
    3. Test for infinite resistance between the appropriate signal circuit terminal listed below and ground:
    • Parameter D1 - terminal 40
    • Parameter D2 - terminal 53
    • Parameter R1 - terminal 38
    • Parameter R2 - terminal 39
    • Parameter S - terminal 54
    • If less than infinite resistance, repair the short to ground on the circuit.
    • If infinite resistance, replace the T6 Power Inverter Module.
    • If all parameters display HIGH 
  5. Vehicle ON.
  6. Install a 3 A fused jumper wire between the low reference circuit terminal 52 and each signal terminal listed below one at a time:
    • Parameter D1 - terminal 40
    • Parameter D2 - terminal 53
    • Parameter R1 - terminal 38
    • Parameter R2 - terminal 39
    • Parameter S - terminal 54
  7. Verify each scan tool hybrid powertrain control module parameter, Internal Mode Switch 2 - D1/D2/R1/R2/S, displays LOW when grounded.
    • If any parameter displays HIGH when grounded 
    1. Vehicle OFF.
    2. Disconnect the X1 harness connector at the T6 Power Inverter Module.
    3. Test for less than 2 Ω in the appropriate signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω
    4. Vehicle ON.
    5. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the T6 Power Inverter Module.
    • If all parameters display LOW when grounded 
  8. Refer to Component Testing .
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