Circuit/System Testing

Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B9 Ambient Air Temperature Sensor. It may take up to 2 min for all vehicle systems to power down.
Test for less than 10 Ω between the low reference circuit terminal B (or 2) and ground.
- If 10 Ω or greater
1. Ignition OFF, disconnect the X2 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.
- Go to next step: If less than 10 Ω
Ignition ON.
Verify the ECM scan tool Ambient Air Temperature parameter reads colder than -30°F (-34°C).
- If -30°F (-34°C) or warmer
1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module.
2. Test for infinite resistance between the signal circuit terminal A (or 1) and ground.
  - If less than infinite resistance, repair the short to ground on the circuit.
  - If infinite resistance, replace the K20 Engine Control Module.
- Go to next step: If colder than -30°F (-34°C)
Install a 3 A fused jumper wire between the signal circuit terminal A (or 1) and the low reference circuit terminal B (or 2).
Verify the scan tool Ambient Air Temperature parameter reads warmer than 180°F (82°C)
- If 180°F (82°C) or colder
1. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module, ignition ON.
2. 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.
  - Go to next step: If less than 1 V
3. Ignition OFF
4. 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.
- Go to next step: If warmer than 180°F (82°C)
Replace the B9 Ambient Air Temperature Sensor.