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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 198 (Manual Transmission - TREMEC 6-Speed (M3L Mg9)) >> Diagnostic Information and Procedures >> DTC P0729 or P0731-P0735: Gear Ratio >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:

Refer to Hot Exhaust System Warning .

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B227 Gear Position Sensor. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the low reference circuit terminal 4 and ground.
    • If 10 Ω or greater 
    1. Disconnect the X3 harness connector at the K20 Engine Control Module.
    2. Test for less than 2 Ω in the 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 less than 10 Ω 
  3. Ignition ON.
  4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the 5 V reference circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the 5 V 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 K20 Engine Control Module.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module, Ignition ON.
    2. Test for less than 1 V between the 5 V reference circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • If between 4.8-5.2 V 
  5. Verify the scan tool Gear Shift Position Sensor parameter duty cycle is greater than 99%.
    • If 99% or less 
    1. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the signal circuit 1 terminal 3 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the K20 Engine Control Module.
    • If greater than 99% 
  6. Install a 3 A fused jumper wire between the signal circuit 1 terminal 3 and ground.
  7. Verify the scan tool Gear Shift Position Sensor parameter duty cycle is less than 1%.
    • If 1% or greater 
    1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the K20 Engine Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit 1 terminal 3 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    3. Ignition OFF.
    4. Test for less than 2 Ω in the signal circuit 1 end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the K20 Engine Control Module.
    • If less than 1% 
  8. Verify the scan tool Gate Select Position Sensor parameter duty cycle is greater than 99%.
    • If 99% or less 
    1. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the signal circuit 2 terminal 2 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the K20 Engine Control Module.
    • If greater than 99% 
  9. Install a 3 A fused jumper wire between the signal circuit 2 terminal 2 and ground.
  10. Verify the scan tool Gate Select Position Sensor parameter duty cycle is less than 1%.
    • If 1% or greater 
    1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the K20 Engine Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit 2 terminal 2 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    3. Ignition OFF.
    4. Test for less than 2 Ω in the signal circuit 2 end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, test or replace the K20 Engine Control Module.
    • If less than 1% 
  11. Install a 3 A fused jumper wire between the signal circuit 1 terminal 3 and ground.
  12. Verify the scan tool Gate Select Position Sensor parameter duty cycle remains greater than 99%.
    • If 99% or less 
    1. Disconnect the X2 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between signal circuit 2 terminal 2 and signal circuit 1 terminal 3 at the B227 Gear Position Sensor wire harness connector.
      • If less than infinite resistance, repair signal circuits shorted together condition.
      • If infinite resistance, replace the K20 Engine Control Module.
    • If greater than 99% 
    13. NOTE:

    The gear position sensor magnet can be viewed when the gear position sensor is removed from the transmission extension housing.

  13. Verify the gear position sensor magnet is undamaged and fastened in proper position on the shift shaft.
    • If the gear position sensor magnet is damaged or out of position 

      Replace the gear position sensor magnet.

    • If the gear position sensor magnet is undamaged and fastened properly on the shift shaft 
  14. Replace the B227 Gear Position Sensor.
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