Diagnostic Test

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

CHECK FOR AN ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, read DTCs and record on the repair order.
  Is the DTC active or pending?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK FOR OTHER DTCS
1. Refer to the recorded DTCs.
  Are there any communication or low voltage DTCs, or is DTC P258A active or pending?
  
  Yes
  - Perform the applicable diagnostic procedure(s). Refer to 3.2L - DIAGNOSTIC CODE INDEX .
  No
  - Go To 3
VERIFY IF THE ENGINE HAS AN ELECTRIC VACUUM PUMP
1. Verify vehicle is equipped with an Electric Vacuum Pump.
  Is the vehicle is equipped with an Electric Vacuum Pump?
  
  Yes
  - Go To 4
  No
  - Go To 14
CHECK THE ELECTRIC VACUUM PUMP FOR PROPER OPERATION
1. Turn the ignition on.
2. With the scan tool actuate the Electronic Vacuum Pump.
  Does the Electric Vacuum Pump run?
  
  Yes
  - Go To 9
  No
  - Go To 5
CHECK THE PDC FOR PROPER OPERATION
1. Turn the ignition off.
2. Remove the Vacuum Pump Relay from the relay connector in the PDC.
3. Turn the ignition on.
4. Using a 12-volt test light connected to ground, probe the Fused RUN/START circuit (terminal 86) at the Vacuum Pump Relay connector.
  Does the test light illuminate brightly?
  
  Yes
  - Go To 6
  No
  - Replace the PDC in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE (T108) ELECTRIC VACUUM PUMP CONTROL OUTPUT CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Disconnect the Electric Vacuum Pump harness connector.
2. Measure the resistance of the (T108) Electric Vacuum Pump Control Output circuit between the Vacuum Pump Relay connector and the Electric Vacuum Pump harness connector.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 7
  No
  - Repair the (T108) Electric Vacuum Pump Control Output circuit for an open.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE (T108) ELECTRIC VACUUM PUMP CONTROL OUTPUT CIRCUIT FOR A SHORT TO GROUND
1. Measure the resistance between ground and the (T108) Electric Vacuum Pump Control Output circuit at the Vacuum Pump Relay connector.
  Is the resistance above 10k Ohms?
  
  Yes
  - Go To 8
  No
  - Repair the (T108) Electric Vacuum Pump Control Output circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE (Z904) GROUND CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Using a 12-volt test light connected to 12 volts, probe the (Z904) Ground circuit at the Electric Vacuum Pump harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Replace the Electric Vacuum Pump in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
  No
  - Repair the (Z904) Ground circuit for an open.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE VACUUM SUPPLY LINE FOR DAMAGE
1. Turn the ignition off.
2. Check the vacuum supply line to brake booster for a pinched, cut or open hose.
  Were any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
  No
  - Go To 10
CHECK THE BRAKE BOOSTER FOR PROPER OPERATION
1. Start the engine.
2. With the scan tool, view and record the vacuum pressure signal with foot off the brake pedal.
3. With the scan tool, view the vacuum pressure signal while pressing the brake pedal several times.
4. Record the highest value.
  Without the brake pedal applied, was the vacuum pressure signal -40 kPa (12 in. Hg)?
  
  Yes
  - Go To 11
  No
  - Replace the Power Brake Booster in accordance with the Service Information. Refer to BOOSTER, POWER BRAKE, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE VACUUM PRESSURE SENSOR FOR PROPER OPERATION
1. Turn the ignition on.
2. Remove the Vacuum Pressure Sensor from the Booster.
3. Connect a vacuum pump to the Vacuum Pressure Sensor.
4. Apply vacuum to the Vacuum Pressure Sensor and watch for signal change.
  Is the voltage signal changing on the scan tool as vacuum is being applied?
  
  Yes
  - Go To 12
  No
  - Replace the Vacuum Pressure Sensor in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE BRAKE BOOSTER CHECK VALVE FOR DAMAGE
1. Remove the Brake Booster Check Valve.
2. Apply vacuum to the booster side of the check valve.
  Is the Brake Booster Check Valve holding vacuum?
  
  Yes
  - Go To 13
  No
  - Replace the Power Brake Booster Check Valve in accordance with the Service Information. Refer to BOOSTER, POWER BRAKE, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE BRAKE BOOSTER FOR PROPER OPERATION
1. Reinstall the Brake Booster Check Valve.
2. Apply vacuum to the Brake Booster.
  Is the Brake Booster holding vacuum?
  
  Yes
  - Go To 14
  No
  - Replace the Power Brake Booster in accordance with the Service Information. Refer to BOOSTER, POWER BRAKE, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
CHECK THE ANTI-LOCK BRAKE SYSTEM (ABS) MODULE FOR PROPER OPERATION
1. Turn the ignition off to the lock position.
2. Perform any Service Bulletins that may apply.
3. Inspect the related wiring harness. Look for any chafed, pierced, pinched or partially broken wires.
4. Inspect the related wire harness connectors. Look for broken, bent, pushed out or corroded terminals.
  Were any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 3.2L . .
  No
  - Replace the Anti-lock Brake System (ABS) Module in accordance with the Service Information. Refer to MODULE, ANTI-LOCK BRAKE SYSTEM (ABS), REMOVAL .
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .