SureTrack Community Fix: Careful Disassembly

Real Fixes from Mitchell 1’s SureTrack┬« expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is available at no additional cost in our ProDemand product.


When following the factory procedures for repairs, be sure to read all the notes, cautions and warnings provide. It might save you some grief in the end. SureTrack community member cgorzsas had a Jeep Liberty in their shop that came in with ABS issues even after repeated attempts to repair it. They posed the question to the community, and with the help of fellow community member Skip and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

Vehicle
2012 Jeep Liberty Sport 3.7L

Title
Repeat failure of HCU, replaced with assembly.

Complaint
Customer complains that ABS light is on.

Diagnostic Steps Performed/Parts Replaced
No speedo function, ABS & Traction lights on with no communication with scan tool and other modules on network. Found bad ABS module
Replaced antilock brake module (ABM) with dealer part. Did initialization and ABS works with good speedo function, but now have code C121D for brake pressure sensor. Brake pressure PID reads -300 psi. Clear code and comes back. Removed module from hydraulic control unit (HCU) and it still reads -300 psi. Do we have a bad module or HCU? Brake pressure sensor may have been damaged when installing module. Procedure did not state module and HCU had to be removed together as assembly. Another source states both must be removed as assembly before module replacement. Is this procedure correct?

Best Answer from Community Member Skip
Found this caution in the procedure provided. When removing ABM from HCU, be sure to completely separate the two components (approximately 38 mm (1.5 inches)) before removing ABM. Otherwise, damage to the pressure sensor will result requiring HCU replacement.

Cause
HCU damaged when separating from ABM.

Correction
We ordered a salvage yard ABS/HCU assembly, installed it as an assembly and bled the brakes. Took for test drive and problem solved. The brake pressure sensor on HCU must be extremely delicate and can be damaged even if you are careful when installing a module.


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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.