P056C

DTC P056C
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC P056C 00: Cruise Control Cancel Switch Circuit Malfunction

Diagnostic Fault Information





Circuit/System Description
The cruise control switch is an input to the body control module (BCM). The BCM monitors the cruise control on/off, set/coast, resume/accelerate and cancel switches via the cruise control switch signal circuit in order to detect when the driver has requested to perform a cruise control function. The BCM detects a specific voltage signal on the cruise control switch signal circuit when a switch is applied. The engine control module (ECM) receives the requested cruise control switch function from the BCM via a serial data message.

Conditions for Running the DTC
The cruise switch is ON.
The engine is running.

Conditions for Setting the DTC
The BCM detects an invalid voltage signal on the cruise control switch signal circuit for greater than 2 s and sends a serial data message to the ECM. The ECM sets these DTCs when the message is received.
The ECM runs this diagnostic every 0.05 s.

Action Taken When the DTC Sets
DTC P056C 00 is a type C DTC.

Conditions for Clearing the DTC
DTC P056C 00 is a type C DTC.

Reference Information
Schematic Reference
Cruise Control Schematics

Connector End View Reference
Component Connector End Views

Description and Operation
Cruise Control Description and Operation

Electrical Information Reference
Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs

DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference
Control Module References for scan tool information

Circuit/System Verification
Engine running, while rotating the steering wheel to both steering stops, observe the scan tool Cruise Control Switch parameter while pressing each of the cruise control switches. The parameter should toggle between On, Off, Resume, Set, and Cancel as the applicable switch is pressed.

Circuit/System Testing
Vehicle OFF, disconnect the harness connector at the S70L steering wheel controls switch - left.
Vehicle in Service Mode, test for B+ between the voltage reference circuit and ground.
If less than the specified value, test the voltage reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
Test for B+ between the voltage reference circuit and the signal circuit.
If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
Vehicle OFF, disconnect the X3 harness connector at the K9 BCM.
Test for infinite resistance between the signal circuit terminal 36 and ground.
If less than the specified value, test the signal circuit for a short to ground.
If all circuits test normal, test or replace the S70L steering wheel controls switch - left.

Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
Cruise Control Switch Replacement
Control Module References for BCM replacement, programming and setup