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Home >> Chevrolet >> 2018 >> Spark LT, Automatic CVT Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 56 (Automatic Transmission - JATCO CVT) >> Diagnostic Information and Procedures >> DTC P0885: Transmission Control Module (TCM) Power Relay Control Circuit >> Circuit/System Testing

Circuit/System Testing

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  1. Ignition OFF, disconnect the K71 Transmission Control Module X1 connector.
  2. Ignition ON, engine OFF.
    NOTE:
    • When test probing harness terminals, it is imperative to use the proper test probe from the most current version of the J 35616  GM-Approved Terminal Test Kit. Use of an improper test probe may deform the terminal, resulting in intermittent open conditions.
    • Testing for step 3 - 4 is performed on the K71 Transmission Control Module X1 harness connector using the J 35616-64B  LT BU probe.
    • Chassis ground to Battery ground 25 - 35 Ω.
  3. Using a fused jumper, test for B+ (+0.0/-1.0 V) between the Transmission Main Relay Control circuit, terminal 16 and chassis ground.
    • If less than B+ (+0.0/-1.0 V) 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A Fuse Block - Underhood.
    2. Test for less than 10 Ω in the affected circuit end to end.
      • If 10 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 10 Ω
    3. Test for infinite resistance between the affected circuit and chassis ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance
    4. Test for infinite resistance between the affected circuit and all other terminals of the X50A Fuse Block - Underhood harness connector X1.
      • If less than infinite resistance, repair the shorted together condition in the affected circuits.
      • If infinite resistance, replace the Transmission Control Module Relay.
    • If B = (+0.0/-1.0 V) 
  4. Using a fused jumper, ground the Transmission Main Relay Control circuit, terminal 16 to chassis ground.
  5. Using a fused jumper, test for B+ (+0.0/-1.0 V) between the following circuits and chassis ground.
    NOTE:
    • NOT grounding the Transmission Main Relay Control circuit, terminal 16 to chassis ground will leave the Transmission Main Relay Fused supply 1 circuits, terminal 5 & 6 at 0 V.
    • Grounding the Transmission Main Relay Control circuit, terminal 16 to chassis ground will energize the relay and cause the Transmission Main Relay Fused supply 1 circuits, terminal 5 & 6 to go to B+ (+0.0/-1.0 V).
    • Transmission Main Relay Fused supply 1 circuit, terminal 5
    • Transmission Main Relay Fused supply 1 circuit, terminal 6
    • If less than B+ (+0.0/-1.0 V) 
    1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block - Underhood.
    2. Test for less than 10 Ω in the affected circuit end to end.
      • If 10 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 10 Ω
    3. Test for infinite resistance between the affected circuit and chassis ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance
    4. Test for infinite resistance between the affected circuit and all other terminals of the X50A Fuse Block - Underhood harness connector X2.
      • If less than infinite resistance, repair the shorted together condition in the affected circuits.
      • If infinite resistance, replace the Transmission Control Module Relay.
    • If B = (+0.0/-1.0 V) 
  6. Ignition OFF, disconnect the K71 Transmission Control Module X2 connector.
  7. Ignition ON, engine OFF.
  8. Using a fused jumper, test for B+ (+0.0/-1.0 V) between the Transmission Main Relay Control circuit, Transmission Control Module X1 connector terminal 16 and the following circuits.
    • Ground circuit, Transmission Control Module X2 connector terminal 11
    • Ground circuit, Transmission Control Module X2 connector terminal 12
    • If less than B+ (+0.0/-1.0 V) 
    1. Ignition OFF, disconnect the G104 ground connector.
    2. Test for less than 10 Ω in the affected circuit end to end.
      • If 10 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 10 Ω
    3. Test for infinite resistance between the affected circuit and chassis ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance
    4. Test for infinite resistance between the affected circuit and all other terminals of the Transmission Control Module X2 connector.
      • If less than infinite resistance, repair the shorted together condition in the affected circuits.
      • If infinite resistance, replace the K71 Transmission Control Module.
    • If B+ (+0.0/-1.0 V) 
  9. Transmission Main Relay Fused supply 1 circuits, Transmission Main Relay Control circuit and Ground circuits OK.
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