Component Testing

WARNING: This page is about a different car, the 2018 Chevrolet Suburban 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

Perform the Circuit/System Testing first.
Ignition Off, remove the transmission fluid pan from the T12 Automatic Transmission Assembly.
Disconnect the X175 harness connector at the T12 Automatic Transmission Assembly.
Disconnect the harness connector at the B15 Transmission Internal Mode Switch.
Connect a jumper wire between the 9 V Reference 1 circuit terminal 10 and each signal circuit listed below one at a time:
- Signal B - Terminal 8
- Signal P - Terminal 9
- Signal S - Terminal 7
Test for infinite resistance between X175 terminal 31 and ground, for each signal circuit.
- If less than infinite resistance
1. Remove the jumper wire.
2. Connect a jumper wire the 9 V Reference 1 circuit terminal 19 and each signal circuit listed below one at a time:
  - Signal B - Terminal 8
  - Signal P - Terminal 17
  - Signal S - Terminal 6
3. Test for infinite resistance between X175 terminal 31 and ground.
  - If less than infinite resistance
    Replace the automatic transmission wiring harness, electrical connector passage sleeve.
  - If infinite resistance
    Replace the transmission control wiring harness.
- Go to next step: If infinite resistance
Connect a jumper wire between the 9 V Reference 1 circuit terminal 10 and each signal circuit listed below one at a time:
- Signal B - Terminal 8
- Signal P - Terminal 9
- Signal S - Terminal 7
Test for less than 2 Ω between X175 and terminal 31 and each signal circuit listed below:
- Signal B - Terminal 28
- Signal P - Terminal 23
- Signal S - Terminal 34
- If greater than 2 Ω
1. Remove the jumper wire.
2. Connect a jumper wire between the 9 V Reference 1 circuit, X176 terminal 19 and each signal circuit listed below one at a time:
  - Signal B - Terminal 3
  - Signal P - Terminal 17
  - Signal S - Terminal 6
3. Test for less than 2 Ω between the 9 V Reference 1 circuit, X175 and each signal circuit listed below one at a time.
  - Signal B - Terminal 28
  - Signal P - Terminal 23
  - Signal S - Terminal 34
  - If greater than 2 Ω
    Replace the automatic transmission wiring harness, electrical connector passage sleeve.
  - If less than 2 Ω
    Replace the transmission control wiring harness.
- Go to next step: If less than 2 Ω
Connect a jumper wire between the 9 V Reference 2 circuit terminal 4 and each signal circuit listed below one at a time:
- Signal A - Terminal 5
- Signal C - Terminal 6
Test for infinite resistance between X175 terminal 29 and ground, for each signal circuit.
- If less than infinite resistance
1. Remove the jumper wire.
2. Connect a jumper wire from the 9 V Reference 2 circuit terminal 5 and each signal circuit listed below one at a time:
  - Signal A - Terminal 2
  - Signal C - Terminal 11
3. Test for infinite resistance between X175 terminal 29 and ground.
  - If less than infinite resistance
    Replace the automatic transmission wiring harness, electrical connector passage sleeve.
  - If infinite resistance
    Replace the transmission control wiring harness.
- Go to next step: If infinite resistance
Connect a jumper wire between the 9 V Reference 2 circuit, X176 terminal 5 and each signal circuit listed below one at a time:
- Signal A - Terminal 2
- Signal C - Terminal 11
Test for less than 2 Ω between X175 and terminal 29 and each signal circuit listed below:
- Signal A - Terminal 22
- Signal C - Terminal 21
- If greater than 2 Ω
1. Remove the jumper wire.
2. Connect a jumper wire between the 9 V Reference 2 circuit, X176 terminal 5 and each signal circuit listed below one at a time:
  - Signal A - Terminal 2
  - Signal C - Terminal 11
3. Test for less than 2 Ω between the 9 V Reference 2 circuit, X175 terminal 29 and each signal circuit listed below one at a time:
  - Signal A - Terminal 22
  - Signal C - Terminal 21
  - If greater than 2 Ω
    Replace the automatic transmission wiring harness, electrical connector passage sleeve.
  - If less than 2 Ω
    Replace the transmission control wiring harness.
- Go to next step: If less than 2 Ω
Connect a jumper wire between terminal 1 and terminal 2.
Test for infinite resistance between X176 terminal 12 and ground.
- If less than infinite resistance
  Replace the transmission control wiring harness.
- If infinite
1. Test for less than 2 Ω between terminal 12 and terminal 20.
2. If 2 Ω or greater, replace the transmission control wiring harness.
- Go to next step: If infinite resistance
Disconnect the jumper wire.
Connect a jumper wire between X176 terminal 12 and terminal 20.
Test for infinite resistance between harness connector X175 terminal 35 and ground.
- If less than infinite resistance
  Replace the automatic transmission wiring harness, electrical connector passage sleeve.
- If infinite
1. Test for less than 2 Ω between terminal 30 and terminal 35.
2. If 2 Ω or greater, replace the automatic transmission wiring harness, electrical connector passage sleeve.
- Go to next step: If infinite resistance
Replace the B15 Transmission Internal Mode Switch.