Diagnostic Test-EBOOSTER Brake System - Pcm

PRELIMINARY DIAGNOSTIC CHECKS 

1. Check the tire and wheel sizes. Mismatched tires and wheels can cause rationality DTCs to set.
2. Check for any Service Bulletins, Star On-line Cases or ECU flash updates that apply for the DTC or symptom.
3. Check for any Battery voltage DTCs in the BSCM. Low Battery voltage can cause DTCs.
4. Circuit faults should typically be diagnosed before rationality/performance faults.

SYSTEM PERFORMANCE FAULTS (P057B, C053D, C10F5):  The signal performance faults set when one of the following signals received from the BSCM is irrational when compared to the others. The rationality checks are only done during a driver initiated braking event, not during an autonomous braking event.

• P057B - Brake Pedal Position signal is irrational.
• C053D - Brake Pedal Pressure signal is irrational.
• C10F5 - Brake Torque signal is irrational.

The Brake Pedal Position Sensor and Brake Pedal Simulator Pressure Sensor are internal to the Hydraulic Assembly. The Brake Torque signal is calculated by the BSCM. The calculation is based on the sum of the hydraulic pressure to the calipers in all four hydraulic circuits. If one of the signals is irrational, the Hydraulic Assembly or BSCM are likely faulty.

1. Verify the BSCM is mounted correctly to the Hydraulic Assembly. Next, remove the BSCM and inspect the terminals for signs of damage (pushed out, spread, corroded or dirty terminals).
   • If the BSCM terminals appear damaged, repair the terminals or replace the BSCM in accordance with the Service Information.
   • If the BSCM and terminals appear good, replace the eBooster assembly in accordance with the Service Information.
   NOTE:

   The Hydraulic Assembly and BSCM are separate components, but may be required to be replaced as an eBooster assembly for a period of time on some vehicles. If the BSCM is suspected to be the failure, always check to see if the BSCM can be replaced separately. If the Hydraulic Assembly is suspected, the entire eBooster assembly should be replaced.

IMPLAUSIBLE DATA FAULTS (U0418, U11BF):  The implausible/lost brake signal faults set when the BSCM detects a fault against both Brake Pedal Position Sensors and has no rational signal to send to the PCM. The implausible data fault sets when the BSCM detects a fault against the Brake Pedal Pressure Sensor and has no rational signal to send to the PCM.

1. Verify the BSCM is mounted correctly to the Hydraulic Assembly. Next, remove the BSCM and inspect the terminals for signs of damage (pushed out, spread, corroded or dirty terminals).
   • If the BSCM terminals appear damaged, repair the terminals or replace the BSCM in accordance with the Service Information.
   • If the BSCM and terminals appear good, replace the eBooster assembly in accordance with the Service Information.
   NOTE:

   The Hydraulic Assembly and BSCM are separate components, but may be required to be replaced as an eBooster assembly for a period of time on some vehicles. If the BSCM is suspected to be the failure, always check to see if the BSCM can be replaced separately. If the Hydraulic Assembly is suspected, the entire eBooster assembly should be replaced.

LOSS OF COMMUNICATION FAULTS (U0121, U0129):  The U0121 fault sets when the PCM does not receive the Brake Pedal Position Sensor signal message from the BSCM and the U0129 fault sets when the PCM does not receive the Brake Pedal Pressure Sensor signal message. Perform the following diagnostic checks for the Brake System Control Module:

1. Check for any Service Bulletins, Star On-line Cases, PCM or BSCM flash updates that apply for the DTC or symptom.
2. Check for any Battery voltage DTCs in the BSCM. Low Battery voltage can cause a DTC.
3. Verify the vehicle modules are configured correctly. An incorrect configuration can cause a Loss of Communication fault.
4. Using the appropriate wiring information as a guide, check the fuse or fuses that supply power to BSCM. Verify the fuse(s) are not open and has a good connection with the terminals in the PDC
   1. If the fuse(s) are good, continue testing in step 5.
   2. If a fuse is open, check the supply circuit for a short to ground before replacing the fuse.

5. Courtesy of CHRYSLER GROUP, LLC

   Disconnect the BSCM harness connector and load test the Battery Supply and Ignition circuits.

   1. A load test is used to determine if a circuit is capable of carrying the amperage needed to perform properly. The 3156 bulb in the load tool illustrated, is a simple but effective method of testing circuit functionality. A 3156 Bulb has approximately 6.0 Ohms of resistance when the bulb is powered and draws approximately 2.0 amps of current. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool and for additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .
   2. To verify that there is no resistance in the circuit being tested, perform a simple voltage drop test across the 3156 bulb of the load test tool. The voltage drop across the bulb should be equal to the voltage reading across the Battery terminals if there is no resistance in the circuit being tested.
      • If either circuit fails the load testing, repair the resistance in the circuit. If the fuse that supplies power to the module is open or damaged
      • If both circuits pass the load test, continue testing in step 6.

6. Courtesy of CHRYSLER GROUP, LLC

   Load test the BSCM Ground circuit.

   1. If the ground circuit fails load testing, repair the BSCM chassis ground.
   2. If the ground circuit tests good, continue testing in step 7.
7. Check the voltage on the CAN Bus (+) and CAN Bus (-) circuits at the BSCM. Typically the CAN Bus (+) voltage should be approximately 2.6v and CAN Bus (-) voltage should be approximately 2.4v.
   1. If the voltage readings do not match the values given above, check the suspect circuit for opens or shorts.
      NOTE:

      A short in a Bus circuit would likely cause a Bus Performance fault or affect several modules. If only one module has Loss of Communication faults logged against it due to a wiring issue, it would likely be due to an open in a Bus circuit in the module harness connector or the wiring leading to that module.

   2. If both voltage readings match the values given, the BSCM is likely faulty. Use the appropriate wiring information to check all related harness connectors for pushed out, spread, corroded or dirty terminals before condemning the BSCM. To check for an intermittent condition, connect a lab scope to both circuits at the BSCM connector and wiggle test to the wiring harnesses monitoring for a drop in either Bus circuit. If no issues are found, replace the BSCM in accordance with the service information.