1999 LAND ROVER DISCOVERY ECU

SUNROOF
76-6-6 DESCRIPTION AND OPERATION
Front sunroof switch
The front sunroof switch is located in the roof console above the windscreen in front of the front sunroof. It controls
the front sunroof motor via the sunroof ECU.
The front sunroof switch supplies an earth signal to the sunroof ECU. The pin at the ECU that receives the earth
signal determines whether ECU causes the sunroof to open or close.
TestBook cannot monitor the state of the front sunroof switch.
The following table lists the values which can be measured at the listed ECU pins when the conditions outlined are
met:
Signal values (connector connected)
Connector/Pin
No.Condition Resistance, ohms
C0784-2 Ignition in position II, front sunroof switch released > 10,000
C0784-2 Ignition in position II, front sunroof switch open < 0.5
C0785-7 Ignition in position II, front sunroof switch released > 10,000
C0785-7 Ignition in position II, front sunroof switch closed < 0.5

SUNROOF
DESCRIPTION AND OPERATION 76-6-7
Front sunroof motor and microswitch
The front sunroof motor is located within the front sunroof assembly. The sunroof ECU controls the front sunroof
motor.
The sunroof ECU determines the direction the sunroof motor runs. A battery signal to one side of the motor and an
earth to the other side of the motor causes the motor to turn in one direction, reversing the polarity through the same
pins causes the motor to turn in the opposite direction.
The following table lists the values which can be measured at the listed ECU pins when the conditions outlined are
met:
Signal values (connector connected)
Connector/Pin
No.Condition Voltage Resistance, ohms
C0785-5 Ignition in position II, rear of front sunroof switch
pressed+voltage to C0785-
5
C0785-1 Ignition in position II, front of front sunroof switch
pressed+voltage to C0785-
1< 0.5
C0784-8 Ignition in position II, sunroof fully closed +V Batt
C0784-8 Ignition in position II, sunroof not closed > 10,0000

SUNROOF
76-6-8 DESCRIPTION AND OPERATION
Rear sunroof - front switch
The rear sunroof front switch is located in the roof console above the windscreen in front of the front sunroof. It
controls the rear sunroof motor via the sunroof ECU.
The rear sunroof front switch supplies an earth signal to the sunroof ECU. The pin at the ECU that receives the earth
signal determines whether ECU causes the sunroof to open or close.
TestBook cannot monitor the state of the rear sunroof front switch.
The following table lists the values which can be measured at the listed ECU pins when the conditions outlined are
met:
Signal values (connector connected)
Connector/Pin
No.Condition Ohms
C0784-7 Ignition in position II, rear sunroof front switch released > 10,000
C0784-7 Ignition in position II, rear sunroof front switch open < 0.5
C0785-8 Ignition in position II, rear sunroof front switch released > 10,000
C0785-8 Ignition in position II, rear sunroof front switch closed < 0.5

SUNROOF
DESCRIPTION AND OPERATION 76-6-9
Rear sunroof isolation switch
The rear sunroof isolation switch is located in the roof console above the windscreen in front of the front sunroof. It
prevents the rear sunroof rear switch from operating the rear sunroof.
The rear sunroof isolation switch is in the earth path between the rear sunroof rear switch and the sunroof ECU.
Operating the rear sunroof isolation switch opens the circuit and prevents the rear sunroof rear switch from operating
the rear sunroof.
TestBook cannot monitor the state of the rear sunroof isolation switch.
The following table lists the values which can be measured at the listed ECU pins when the conditions outlined are
met:
Signal values (connector connected)
Connector/Pin
No.Condition Resistance, ohms
C0784-6 Ignition in position II, rear sunroof rear switch open, rear
sunroof isolation switch pressed> 10,000
C0784-6 Ignition in position II, rear sunroof rear switch open, rear
sunroof isolation switch released< 0.5
C0785-9 Ignition in position II, rear sunroof rear switch closed, rear
sunroof isolation switch pressed> 10,000
C0785-9 Ignition in position II, rear sunroof rear switch closed, rear
sunroof isolation switch released< 0.5

SUNROOF
76-6-10 DESCRIPTION AND OPERATION
Rear sunroof rear switch
The rear sunroof rear switch is located in the roof console in front of the rear sunroof. It controls the rear sunroof
motor via the sunroof ECU.
The rear sunroof front switch supplies an earth signal through the rear sunroof isolation switch to the sunroof ECU.
The pin at the ECU that receives the earth signal determines whether ECU causes the sunroof to open or close.
TestBook cannot monitor the state of the rear sunroof rear switch.
The following table lists the values which can be measured at the listed ECU pins when the conditions outlined are
met:
Signal values (connector connected)
Connector/Pin
No.Condition Resistance, ohms
C0784-6 Ignition in position II, rear sunroof isolation switch closed, rear
sunroof rear switch released> 10,000
C0784-6 Ignition in position II, rear sunroof isolation switch closed, rear
sunroof front switch open< 0.5
C0785-9 Ignition in position II, rear sunroof isolation switch closed, rear
sunroof front switch released> 10,000
C0785-9 Ignition in position II, rear sunroof isolation switch closed, rear
sunroof front switch closed< 0.5

SUNROOF
DESCRIPTION AND OPERATION 76-6-11
Rear sunroof motor and microswitch
The rear sunroof motor and microswitch are located within the rear sunroof assembly. The sunroof ECU controls the
rear sunroof motor.
The sunroof ECU determines the direction the sunroof motor runs. A battery signal to one side of the motor and an
earth to the other side of the motor causes the motor to turn in one direction, reversing the polarity through the same
pins causes the motor to turn in the opposite direction.
Operating Parameters (connector connected)
Connector/Pin
No.Condition Voltage Resistance, ohms
C0785-4 Ignition in position II, rear of rear sunroof switch pressed +voltage to C0785-
6
C0785-6 Ignition in position II, front of rear sunroof switch
pressed+voltage to C0785-
4< 0.5
C0784-2 Ignition in position II, sunroof fully closed +V Batt
C0784-2 Ignition in position II, sunroof not closed > 10,0000

SUNROOF
76-6-12 DESCRIPTION AND OPERATION
Sunroof ECU
The sunroof ECU is located behind the head lining above the rear view mirror. Most functions of the sunroof ECU are
covered under other components.
Sunroof ECU connector pin details - C0784
Sunroof ECU connector pin details - C0785
Pin No. Description Input/Output
1 Rear sunroof microswitch Input
2 Front sunroof switch - open Input
3 Not used -
4 Sunroof microswitches - common Input
5 Not used -
6 Rear sunroof, rear switch - open Input
7 Rear sunroof, front switch - open Input
8 Front sunroof microswitch Input
Pin No. Description Input/Output
1 Front sunroof motor forward Output
2 ECU earth Input
3 Battery power supply Input
4 Rear sunroof motor backwards Output
5 Front sunroof motor backwards Output
6 Rear sunroof motor forwards Output
7 Front sunroof switch - close Input
8 Rear sunroof, front switch - close Input
9 Rear sunroof, rear switch - close Input
10 Sunroof enable Input

SUNROOF
DESCRIPTION AND OPERATION 76-6-13
Operation
Ignition switched-off timeout
There are three timeout modes for operating the sunroof assemblies after the ignition is switched off. The BCU
determines the vehicle's timeout mode. The three modes are:
lWhen the ignition is switched off, no sunroof operation is permitted.
lWhen the ignition is switched off, sunroof remains functional for 45 seconds or until the driver door is opened.
lWhen the ignition is switched off, sunroof remains functional for 45 seconds or until any door is opened.
Sunroof open and close
Both sunroof assemblies operate in the same manner. The front sunroof assembly has one switch while there are
two switches to control rear sunroof assembly, a rear sunroof front switch and a rear sunroof rear switch.
The sunroof ECU monitors the position of the sunroof microswitch to determine if the sunroof is to be tilted or opened.
In order for the sunroof to operate, either of the following conditions must exist:
lIgnition switch in position II.
lIgnition switched from on to off, doors closed (this may enable the system to operate for 45 seconds after the
ignition is switched off, or until a door is opened).
When the sunroof is closed, pressing the rear of the sunroof switch causes the sunroof ECU to operate the sunroof
motor and open the sunroof. When the sunroof opens, the sunroof microswitch opens. The sunroof continues to
open until the switch is released or the sunroof reaches the fully open position.
When the sunroof is open, pressing the front of the sunroof switch causes the sunroof ECU to operate the sunroof
motor and close the sunroof. The sunroof ECU continues to operate the motor until the sunroof microswitch closes.
This indicates to the sunroof ECU that the sunroof is fully closed.
Sunroof tilt
Both sunroof assemblies operate in the same manner. The front sunroof assembly has one switch while there are
two switches to control rear sunroof assembly, a rear sunroof front switch and a rear sunroof rear switch.
The sunroof ECU monitors the position of the sunroof microswitch to determine if the sunroof is to be tilted or opened.
In order for the sunroof to operate, either of the following conditions must exist.
lIgnition in position II.
lIgnition switched from on to off, doors closed (this may enable the system to operate for 45 seconds after the
ignition is switched off, or until a door is opened).
When the sunroof is closed and the front of the sunroof switch is pressed, the sunroof ECU detects the combination
of closed microswitch and front of sunroof switch being pressed and tilts the rear of the sunroof. This causes the
microswitch to open. The sunroof continues to open until the switch is released or the sunroof reaches the fully open
position.
When the sunroof is tilted and the rear of the sunroof switch is pressed, the sunroof ECU detects the combination of
open microswitch and rear of sunroof switch and closes the sunroof until the microswitch closes. This indicates to the
sunroof ECU that the sunroof is fully closed.
Rear sunroof isolation
The rear sunroof isolation switch prevents the rear sunroof rear switch from operating the rear sunroof. This can be
used to prevent small children sitting in the rear seat from playing with the rear sunroof.
Pressing the rear sunroof isolation switch opens the circuit between the rear sunroof rear switch and the sunroof ECU.
The sunroof ECU ignores the rear sunroof switch until the rear sunroof isolation switch is pressed and the circuit
closes.