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. With the scan tool, read Body Control Module (BCM) DTCs and record on the repair order.
2. Record the Environmental Data and any DTCs.
3. With the scan tool, erase DTCs.
4. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
5. With the scan tool, read BCM DTCs.
  Did the DTC return?
  
  Yes
  - Go To 2
  No
  - Test complete. The condition or conditions that originally set this DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals and correct pin tension.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
CHECK FOR VOLTAGE ON THE (B20) BRAKE FLUID LEVEL SIGNAL CIRCUIT
1. Turn the ignition off.
2. Disconnect the Brake Fluid Level Switch harness connector.
3. Turn the ignition on.
4. Measure the voltage on the (B20) Brake Fluid Level Signal circuit at the Brake Fluid Level Switch harness connector.
  Is there any voltage present?
  
  Yes
  - Go To 3
  No
  - Go To 6
CHECK THE (Z905) GROUND CIRCUIT FOR AN OPEN
1. Turn the ignition off.
2. Measure the resistance of the (Z905) Ground circuit between ground and the Brake Fluid Level Switch harness connector.
  Is the resistance above 3.0 Ohms?
  
  Yes
  - Repair the open in the (Z905) Ground circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 4
CHECK THE (B20) BRAKE FLUID LEVEL SIGNAL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT IN THE HARNESS CONNECTOR
1. Turn the ignition off.
2. Disconnect the BCM C4 harness connector.
3. Check for continuity between the (B20) Brake Fluid Level Signal circuit and all other circuits on the BCM C4 harness connector.
  Is there continuity between the (B20) Brake Fluid Level Signal circuit and any other circuit(s)?
  
  Yes
  - Repair the short between the (B20) Brake Fluid Level Signal circuit and the circuit that has continuity.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 5
CHECK THE BCM FOR PROPER OPERATION
1. Turn the ignition off.
2. Connect the BCM C4 harness connector.
3. Connect a jumper wire between the (B20) Brake Fluid Level Signal circuit and the (Z905) Ground circuit at the Brake Fluid Level Switch harness connector.
4. Turn the ignition on.
5. With the scan tool, read the Brake Fluid Level.
  Does the Brake Fluid Level display Low?
  
  Yes
  - Replace the Brake Fluid Level Switch in accordance with the Service Information. Refer to SWITCH, BRAKE FLUID LEVEL, REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 7
CHECK THE (B20) BRAKE FLUID LEVEL SIGNAL CIRCUIT FOR AN OPEN
1. Disconnect the BCM C4 harness connector.
2. Measure the resistance of the (B20) Brake Fluid Level Signal circuit between the BCM C4 harness connector and the Brake Fluid Level Switch harness connector.
  Is the resistance above 3.0 Ohms?
  
  Yes
  - Repair the open in the (B20) Brake Fluid Level Signal circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 7
CHECK RELATED BCM HARNESS CONNECTIONS
1. Disconnect all BCM harness connectors.
2. Disconnect all related in-line harness connections (if equipped).
3. Disconnect the related component harness connectors.
4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
  - Proper connector installation.
  - Damaged connector locks.
  - Corrosion.
  - Other signs of water intrusion.
  - Weather seal damage (if equipped).
  - Bent terminals.
  - Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
  - Terminals that have been pushed back into the connector cavity.
  - Check for spread terminals and verify proper terminal tension.
  Repair any conditions that are found.
5. Connect all BCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
7. Connect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. With the scan tool, erase DTCs.
9. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
10. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Replace the Body Control Module (BCM) in accordance with the Service Information. Refer to MODULE, BODY CONTROL (BCM), REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - The wiring or poor connection problem has been repaired.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .