Circuit/System Testing

Verify the brake booster vacuum system has none of the conditions listed below:
- Vacuum leak or Weak Vacuum
- Damaged, defective, or loose component:
- If a condition exists
  Refer to: Brake Assist System Diagnosis
- Go to next step: If no condition exists
NOTE:
It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

Ignition/Vehicle & All vehicle systems - Off
Disconnect the electrical connector: B19B Brake Booster Vacuum Sensor
Test for less than 10 ohms between the test points: Low Reference circuit terminal 2 & Ground
- If 10 ohms or greater
1. Disconnect the electrical connector: K20 Engine Control Module
2. Test for less than 2 ohms between the test points: Low Reference circuit terminal 2 @ Component harness & The other end of the circuit @ Control module harness
  - If 2 ohms or greater - Repair the open/high resistance in the circuit.
  - If less than 2 ohms - Replace the component: K20 Engine Control Module
- Go to next step: If less than 10 ohms
Ignition - On / Vehicle - In Service Mode
Test for 4.8 to 5.2 V between the test points: 5 V Reference circuit terminal 3 & Low Reference circuit terminal 2
- If less than 4.8 V
1. Ignition/Vehicle - Off
2. Disconnect the electrical connector: K20 Engine Control Module
3. Test for infinite resistance between the test points: 5 V Reference circuit terminal 3 @ Component harness & Ground
  - If less than infinite resistance - Repair the short to ground on the circuit.
  - Go to next step: If infinite resistance
4. Test for less than 2 ohms between the test points: 5 V Reference circuit terminal 3 @ Component harness & The other end of the circuit @ Control module harness
  - If 2 ohms or greater - Repair the open/high resistance in the circuit.
  - If less than 2 ohms - Replace the component: K20 Engine Control Module
- If greater than 5.2 V
1. Ignition/Vehicle - Off
2. Disconnect the electrical connector: K20 Engine Control Module
3. Ignition - On / Vehicle - In Service Mode
4. Test for less than 1 V between the test points: 5 V Reference circuit terminal 3 @ Component harness & Ground
  - If 1 V or greater - Repair the short to voltage on the circuit.
  - If less than 1 V - Replace the component: K20 Engine Control Module
- Go to next step: If between 4.8 and 5.2 V
Test for less than 1 V between the test points: Signal circuit terminal 1 @ Component harness & Ground
- If greater than 1 V
Ignition/Vehicle - Off
Disconnect the electrical connector: K20 Engine Control Module
Ignition - On / Vehicle - In Service Mode
Test for less than 1 V between the test points: Signal circuit terminal 1 @ Component harness & Ground
- If 1 V or greater - Repair the short to voltage on the circuit.
- If less than 1 V - Replace the component: K20 Engine Control Module
- Go to next step: If less than 1 V
1. Disconnect the electrical connector: K20 Engine Control Module
2. Test for infinite resistance between the test points: Signal circuit terminal 1 @ Component harness & Ground
  - If less than infinite resistance - Repair the short to ground on the circuit.
  - Go to next step: If infinite resistance
Test for less than 2 ohms between the test points: Signal circuit terminal 1 @ Component harness & The other end of the circuit @ Control module harness
- If 2 ohms or greater
  Repair the open/high resistance in the circuit.
- Go to next step: If less than 2 ohms
Test or replace the component: B19B Brake Booster Vacuum Sensor
If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not set.
- If the DTC sets
  Test or replace the component: K20 Engine Control Module
- Go to next step: If the DTC does not set
All OK.