Troubleshooting the Terrain Response System (Discovery 3)

System control unit "Terrain Response" stores information about detected system faults "Terrain Response" and CAN bus errors, which can be read using T4. Subsystems "Terrain Response" and the instrument cluster also store information about faults associated with CAN bus errors when exchanging data with the system control unit "Terrain Response".

In addition, the control unit stores the mileage and operating time in the highest stage for individual programs and in the lowest stage for all programs. This information can also be read using T4. This information simplifies system diagnostics. "Terrain Response" and allows to detect incorrect use of the system "Terrain Response", which can lead to premature failure of components.

System operation "Terrain Response" depends on five subsystems. In case of failure of one of the subsystems, the system "Terrain Response" stops working even if the fault is not related to the system itself "Terrain Response". Troubleshooting the control unit and rotary switch of the system "Terrain Response" should only be performed if there are no obvious faults in any of the subsystems. When troubleshooting a subsystem, the system "Terrain Response" will resume normal operation after turning the ignition on and off.

Subsystem failures "Terrain Response"

When a fault is detected in a subsystem, the corresponding indicator lights up and/or a message corresponding to the subsystem is displayed on the instrument cluster message center display. System fault warning "Terrain Response" not served.



If the subsystem is faulty and the driver tries to select another program "Terrain Response" using the rotary switch or after the next ignition switch is turned on, the message center display shows 'SYSTEM FAULT SPECIAL PROGRAMS NOT AVAILABLE' (SYSTEM MALFUNCTION. SPECIAL PROGRAMS NOT AVAILABLE). This means that the system "Terrain Response" is faulty, but this is only due to a fault in the subsystem. This message is displayed for 5 seconds after each ignition on/off cycle and is re-displayed if the driver attempts to select a program using the rotary switch of the system "Terrain Response", as well as after each subsequent ignition switch-on.

NOTE: Also message "SYSTEM FAULT SPECIAL PROGRAMS NOT AVAILABLE" (SYSTEM MALFUNCTION. SPECIAL PROGRAMS NOT AVAILABLE) may be displayed in case of a malfunction of the rotary switch or the control unit of the system "Terrain Response". Rotary switch and control unit faults are discussed in the next section.

System control unit "Terrain Response" cannot cause a malfunction (which is indicated by the indicator turning on or the message being displayed) none of the five subsystems. The illumination of a subsystem indicator and/or the output of a subsystem-related message cannot be related to the system control unit "Terrain Response" or to a system malfunction "Terrain Response".

Subsystem control units can detect CAN signal failures when exchanging data with the system control unit "Terrain Response". If a system malfunction is registered "Terrain Response", the subsystem control units will operate in a mode without special programs. The subsystem control units save fault codes in case of a CAN system signal failure "Terrain Response". Information about these faults can be read using T4. It is useful for diagnosing the control unit of the system. "Terrain Response" and CAN networks.

Rotary switch and control unit malfunctions "Terrain Response"

In case of malfunction of the rotary switch of the system "Terrain Response" all yellow LED symbols on the rotary switch go out (background lighting remains), and the system does not respond to the rotary switch. The message appears on the instrument cluster message center display. "SYSTEM FAULT SPECIAL PROGRAMS NOT AVAILABLE" (SYSTEM MALFUNCTION. SPECIAL PROGRAMS NOT AVAILABLE) at the moment of detection of a malfunction, in the presence of a malfunction and an attempt to select a special program (if the control unit can perform this operation), and also the next time the ignition is turned on.

If the yellow LED indicator of the rotary switch fails, the system "Terrain Response" continues to operate. Each time the ignition is turned on, all special programs are turned off, except for the "Grass/Gravel/Snow" program.

Rotary switch and control unit of the system "Terrain Response" are a single unit. If one of the components fails, the entire unit must be replaced.

CAN bus faults

In case of a CAN bus malfunction that prevents the system from operating normally "Terrain Response", the LEDs of all symbols on the rotary switch turn on and the system does not respond to rotation of the rotary switch.

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If the instrument cluster does not receive messages from the system control unit via the CAN bus "Terrain Response", at the moment of registration of the malfunction and each subsequent time the ignition is turned on, a message appears "SYSTEM FAULT SPECIAL PROGRAMS NOT AVAILABLE" (SYSTEM MALFUNCTION. SPECIAL PROGRAMS NOT AVAILABLE).

User errors

The system's reaction to the following incorrect user actions may be considered a system malfunction:

• The engine is not running: changing programs and displaying information messages is only possible when the engine is running.
• The "Slow movement on rocky surface" program is selected, but the transfer case is in the highest gear.
• An attempt is made to change a special program with the dynamic stabilization system or anti-lock braking system enabled. (including switching on/off the anti-lock braking system, which operates when using the hill descent control system on slippery or loose surfaces).
• An attempt is made to change a special program when the center or rear differential overheats.