Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSJEEP2013COMPASS SPORT, 2.4L ENG VIN B, FWD, STANDARD TRANSREPAIR AND DIAGNOSIS (SINGLE PAGE)BRAKESANTI-LOCK BRAKES(ANTILOCK BRAKE SYSTEM (ABS) - ELECTRICAL DIAGNOSTICS)DTC TROUBLESHOOTINGC121E-BRAKE PRESSURE SENSOR COMPARATIVE PERFORMANCEDIAGNOSTIC TEST
2013 Jeep Compass Sport, 2.4L Eng VIN B, FWD, Standard Trans
Diagnostic Test
2013 Jeep Compass Sport, 2.4L Eng VIN B, FWD, Standard TransSECTION Diagnostic Test
- CHECK FOR A DTC C121E-BRAKE PRESSURE SENSOR COMPARATIVE PERFORMANCE NOTE:
This DTC must be active for the results of this test to be valid.
- Turn the ignition on.
- With the scan tool, read and record the DTCs.
- With the scan tool, read and record the Environmental Data to help identify the conditions in which the DTC was set.
- With the scan tool, erase the DTCs.
- Start the engine.
- Slowly press and release the brake pedal.
- With the scan tool, read and record the DTCs.
Does the scan tool display: C121E-BRAKE PRESSURE SENSOR COMPARATIVE PERFORMANCE?
Yes
- Go To 2
No
- Perform the ABS-INTERMITTENT CONDITION TEST. Refer to ABS-INTERMITTENT CONDITION .
- HCU/ECU ISOLATION
- Turn the ignition off.
- Separate the ECU from the HCU.
- Turn the ignition on.
- With the scan tool, monitor the brake pressure.
Does the scan tool display brake pressure above 218 bar (3162 psi)?
Yes
- Replace the HCU in accordance with the Service Information.
- Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
No
- Replace the ECU in accordance with the Service Information.
- Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.