Pinpoint Tests BD: A Hill Descent Control System Message Is Never/Always On (Raptor Only)
Instrumentation, Message Center and Warning Chimes
Pinpoint Tests
Pinpoint Test BD: A Hill Descent Control System Message Is Never/Always On (Raptor Only)
Normal Operation
The hill descent control system is used to maintain vehicle speed on a downhill grade at operating speeds between 3 km/h (2 mph) and 32 km/h (20 mph). The system goes into standby mode on a flat or uphill terrain. The system deactivates at speeds above 64 km/h (40 mph). During periods of sustained use, the hill descent control system may automatically deactivated in order to cool the braking system.
The hill descent mode is activated by a switch located on the center console. When the switch is pressed, a ground signal is sent to the PCM. The PCM then sends a message to the ABS module along the HS-CAN bus requesting system activation. The ABS module uses input from the Restraints Control Module (RCM) and wheel speed sensors to determine the mode of operation.
The Instrument Cluster (IC) receives the hill descent control status from the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus. The message center displays hill descent control messages to inform the driver that they have entered or exited various states of the hill descent control function.
If the hill descent control system message is missing for less than 5 seconds, the IC defaults the hill descent control system message to the last on/off state, based upon the last known good hill descent control system status message.
NOTE: If DTC U0140 is set in the IC, other symptoms may also be present such as Tire Pressure Monitoring System (TPMS), instrument panel backlighting, and door ajar indication.
If the hill descent control system message status messages are missing for more than 5 seconds, the IC sets DTC U0140 and defaults the hill descent control system message on. If the IC does not receive the ABS status message or the EBD message from the ABS module for more than 5 seconds, the IC sets DTC U0121 and defaults the ABS warning indicator on.
This pinpoint test is intended to diagnose the following:
- ABS module
- Message center concern
PINPOINT TEST BD: A HILL DESCENT CONTROL MESSAGE IS NEVER/ALWAYS ON
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BD1 CHECK THE MESSAGE CENTER WARNING INDICATOR FUNCTION
- Close all doors and hood.
- Ignition ON.
- Open the driver door while monitoring the door ajar message center displays.
- Does the door ajar message center warning indicator display?
Yes
GO to BD2.
No
GO to Pinpoint Test AF. Pinpoint Tests AF: The Message Center Is Not Operating Correctly
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BD2 CHECK AND ENSURE THAT THE HILL DESCENT CONTROL MODE FUNCTIONS
- Start the engine.
- Drive the vehicle between 3 km/h (2 mph) and 32 km/h (20 mph) on a downhill grade and activate the hill descent control system mode.
- Are the brakes applying on a downhill grade?
Yes
GO to BD3.
No
REFER to Antilock Brakes / Traction Control Systems to diagnose ABS system concerns.
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BD3 RETRIEVE THE RECORDED DTCs FROM THE IC SELF-TEST
- Check for recorded DTCs from the IC self-test.
- Is DTC U0121 recorded?
Yes
GO to Pinpoint Test AS. Pinpoint Tests AS: DTC U0121
No
GO to BD4.
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BD4 RETRIEVE THE RECORDED DTCs FROM THE ABS CONTROL MODULE SELF-TEST
- Check for recorded ABS module DTCs from the self-test.
- Are any DTCs recorded?
Yes
REFER to Antilock Brakes / Traction Control Systems.
No
INSTALL a new ABS control module. REFER to Antilock Brakes / Traction Control Systems.
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