Problem: This vehicle was towed in because
the power steering was working one day, and when the owner got in
to drive it the next morning, the power steering didn’t work.
Details: The technician connected a scan
tool to check for diagnostic trouble codes (DTCs). He found two
active data communication codes. One stored in the transmission
control module (TCM), the other in the body control module (BCM).
U0121 – (TCM) NO COMMUNICATION WITH ELECTRONIC BRAKE CONTROL
U0131 – (BCM) NO COMMUNICATION WTH POWER STEERING CONTROL MODULE
Since the technician didn’t have a lot of experience with “U”
codes, he called ALLDATA Tech-Assist for some advice and
The Tech-Assist consultant suggested first checking the fuses,
power and grounds at the power steering control module. Then he
advised checking for good communication lines to and from the
module by load testing those circuits.
The testing verified that all power and grounds were good at
module but there was no voltage on the “serial data communication
enable” (wake-up) circuit. In the colored wiring diagram, it’s
the LT/BLU wire (circuit 5986 from BCM to the ABS module pin #8
or power steering module pin #1). The BCM uses this circuit to
wake up those modules. NOTE: Splice J311 is the
common link between the two DTCs.
The tech found splice J311 corroded under driver sill plate,
located on the driver side just where the driver put his left
Confirmed Repair: He repaired the splice
and communication was restored. After clearing both the DTCs, he
test-drove the vehicle. All issues are resolved and the DTCs did