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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 P0502 or P0503: Vehicle Speed Sensor (M3L) >> 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.
  1. Ignition OFF, and all vehicle systems OFF, disconnect the harness connector at the B115 Vehicle Speed Sensor. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the low reference circuit terminal C and ground.
    • If 10 Ω or greater 
    1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control 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 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 A 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. Ignition OFF, connect the test leads of the J 38522  Vehicle Signal Generator as follows.
    • Red test lead to the signal circuit terminal B at the B115 Vehicle Speed Sensor harness connector.
    • Black test lead to ground at the transmission case.
    • Signal generator double black power cord to B+ and ground.
  6. Set and adjust the J 38522  Vehicle Signal Generator to the following switch positions.
    • Signal switch to 5 V
    • Frequency switch to 600 Hz
    • Duty cycle switch to 50% or normal position
  7. Ignition ON.
  8. Verify the scan tool vehicle speed sensor parameter displays between 100-113 km/h (62-70 mph).
    • If not between 100-113 km/h (62-70 mph) 
    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 signal circuit terminal B 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 infinite resistance between the signal circuit terminal B and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    5. Test for less than 2 Ω in the signal 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 between 100-113 km/h (62-70 mph) 
  9. Replace the B115 Vehicle Speed Sensor.
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