Circuit/System Testing

Vehicle OFF, disconnect the harness connector at the A20 radio/HVAC controls.
Test for less than 10 Ω between the ground circuit terminal 17 and ground.
- If 10 Ω or greater
1. Vehicle OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, repair the open/high resistance in the ground connection.
- If less than 10 Ω
Test for less than 20 Ω between the data shield circuit terminal 3 and ground.
- If 20 Ω or greater
1. Vehicle OFF, disconnect the X1 connector at the A11 radio.
2. Test for less than 2 Ω in the data shield circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, replace the A11 radio.
- If less than 20 Ω
Verify that a test lamp illuminates between the B+ circuit terminal 10 and ground.
- If the test lamp does not illuminate and the circuit fuse is good
1. Vehicle OFF.
2. Test for less than 2 Ω in the B+ circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, refer to Power Mode Mismatch .
- If the test lamp does not illuminate and the circuit fuse is open
1. Vehicle OFF.
2. Test for infinite resistance between the B+ circuit and ground.
  - If less than infinite resistance, repair the short to ground on the circuit.
  - If infinite resistance, replace the A20 radio/HVAC controls.
- If the test lamp illuminates.
Vehicle in Service Mode.
Test for 2-3 V between the serial data circuit terminals listed below and ground.
- terminal 1
- terminal 2
- If less than 2 V
1. Vehicle OFF, disconnect the X1 harness connector at the A11 radio.
2. Test for infinite resistance between the serial data 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 serial data circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, replace the A11 radio.
- If greater than 3 V
1. Vehicle OFF, disconnect the X1 harness connector at the A11 radio. Vehicle in Service Mode.
2. Test for less than 1 V between the serial data circuit and ground.
  - If 1 V or greater, repair the short to voltage on the circuit.
  - If less than 1 V, replace the A11 radio.
- If between 2-3 V
Test for less than 1 V between the control circuit terminals listed below and ground.
- terminal 4
- terminal 15
- If greater than 1 V
1. Vehicle OFF, disconnect the X1 harness connector at the A11 radio. Vehicle in Service Mode.
2. Test for less than 1 V between the control circuit and ground.
  - If 1 V or greater, repair the short to voltage on the circuit.
  - If less than 1 V, replace the A11 radio.
- If less than 1 V
Vehicle OFF, disconnect the X1 harness connector at the A11 radio.
Test for infinite resistance between the control circuit terminals listed below and ground.
- A20 radio/HVAC controls terminal 4
- A20 radio/HVAC controls terminal 15
- If less than infinite resistance,
  Repair the short to ground on the circuit.
- If infinite resistance
Test for less than 2 Ω between the control circuits listed below.
- A20 radio/HVAC controls terminal 4 and the A11 radio terminal 13 X1
- A20 radio/HVAC controls terminal 15 and the A11 radio terminal 27 X1
- If 2 Ω or greater
  Repair the open/high resistance in the circuit.
- If less than 2 Ω.
Replace the A20 radio/HVAC controls. Connect all harness connectors.
Vehicle in Service Mode, radio ON.
Verify that all radio controls operate and perform the correct function.
- If the radio controls still malfunction.
  Replace the A11 radio.
- If all radio controls operate and perform the correct function.
All OK