Pinpoint Test AE: The Hill Descent Indicator Is Never/Always On

Instrumentation, Message Center and Warning Chimes

Pinpoint Test AE: The Hill Descent Indicator Is Never/Always On

Normal Operation

When the hill descent control switch is pressed, a ground signal is provided to the Instrument Panel Cluster (IPC) through the hill descent control circuit. The IPC (Instrument Panel Cluster) then sends a message to the ABS module over the High Speed Controller Area Network (HS-CAN) communication bus requesting system activation. The ABS module enables the hill descent control system and sends the IPC (Instrument Panel Cluster) an indicator request to turn on the hill descent indicator.

The message center provides the specific messages that indicates whether the hill descent system is active mode, fault mode or in the brake cool down mode. For a list of messages, refer to Information And Message Center Information And Message Center description and operation.

If the hill descent control system message is missing for less than 5 seconds, the IPC (Instrument Panel Cluster) 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.

If the hill descent indicator request message is missing for less than 5 seconds, the hill descent indicator remains in the last indication state (on or off) based upon the last known good message received. If the hill descent indicator request message is missing for more than 5 seconds or longer, the IPC (Instrument Panel Cluster) sets DTC U0121:00 and defaults the hill descent indicator off.

This pinpoint test is intended to diagnose the following:

- ABS module

- IPC (Instrument Panel Cluster)

PINPOINT TEST AE : THE HILL DESCENT INDICATOR IS NEVER/ALWAYS ON

AE1 CHECK THE HILL DESCENT CONTROL MODE FUNCTION

- 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.

Does the hill descent control system function correctly and slow the vehicle?

Yes
GO to AE2.

No
To diagnose the hill descent system, REFER to Antilock Brakes / Traction Control Systems.

AE2 CARRY OUT THE IPC (Instrument Panel Cluster) WARNING LAMPS COMMAND USING THE SCAN TOOL

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: IPC (Instrument Panel Cluster) DataLogger.

- Select the IPC (Instrument Panel Cluster) hill descent indicator (HDC_ACTIVE) active command. Command the hill descent indicator on and off. Observe the hill descent indicator.

Does the hill descent indicator illuminate when commanded on, and turn off when commanded off?

Yes
GO to AE3.

No
INSTALL a new IPC (Instrument Panel Cluster). REFER to Instrument Panel Cluster (IPC) . TEST the system for normal operation.

AE3 RETRIEVE THE RECORDED DTCs FROM THE IPC (Instrument Panel Cluster) SELF-TEST

- Check for recorded DTCs from the IPC (Instrument Panel Cluster) self-test.

Is DTC U0121:00 recorded?

Yes
GO to Pinpoint Test BD. Pinpoint Test BD: DTC U0121:00
No
GO to AE4.

AE4 RETRIEVE THE RECORDED DTCs FROM THE ABS 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 module. TEST the system for normal operation.