Circuit/System Testing

NOTE:

Use the schematics and connector end views to identify the device's ground, B+, ignition, accessory wake up serial data, and serial data circuit terminals.

Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the harness connectors at the K20 Engine Control Module. It may take up to 2 min for all vehicle systems to power down.
Test for less than 10 Ω between each ground circuit terminal and ground.
- If 10 Ω or greater
1. Ignition 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
Ignition ON.
If equipped, verify a test lamp illuminates between each B+ circuit terminal and ground.
- If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF, remove the test lamp.
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, verify the fuse is not open and there is voltage at the fuse.
- If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF, remove the test lamp.
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 K20 Engine Control Module.
- If the test lamp illuminates
If equipped, verify a test lamp illuminates between each ignition circuit terminal and ground.
- If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF, remove the test lamp.
2. Test for less than 2 Ω in the ignition circuit end to end.
  - If 2 Ω or greater, repair the open/high resistance in the circuit.
  - If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.
- If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF, remove the test lamp.
2. Test for infinite resistance between the ignition circuit and ground.
  - If less than infinite resistance, repair the short to ground on the circuit.
  - If infinite resistance, replace the K20 Engine Control Module.
- If the test lamp illuminates
If equipped, verify a test lamp illuminates between the accessory wakeup serial data circuit terminal and ground.
- If the test lamp does not illuminate
1. Ignition OFF, remove the test lamp, disconnect the harness connectors at the K9 Body Control Module.
2. Test for infinite resistance between the accessory wakeup 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 accessory wakeup 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 K9 Body Control Module.
- If the test lamp illuminates
Ignition OFF, all access doors closed, all vehicle systems OFF, and all keys at least 3 m (9.8 ft) away from vehicle. Disconnect the harness connectors at the K111 Fuel Pump Driver Control Module. It may take up to 2 min for all vehicle systems to power down.
Test for less than 2 Ω in each serial data circuits end to end between the K20 Engine Control Module and the K111 Fuel Pump Driver Control Module.
- If 2 Ω or greater
  Repair the open/high resistance in the serial data circuit.
- If less than 2 Ω
Replace the K20 Engine Control Module.