Discovery 2. Manual - part 570
AUTOMATIC GEARBOX - ZF4HP22 - 24
DESCRIPTION AND OPERATION
44-19
After the detection of a fault, the effects remain active for the remainder of the drive cycle. In subsequent drive cycles,
as soon as the EAT ECU diagnoses the fault is no longer present, it resumes normal control of the gearbox. The
conditions required to diagnose that the fault is no longer present depend on the fault. Some faults require the engine
to be started, others require only that the ignition is switched on.
After a fault has not recurred for forty warm-up cycles, the fault is deleted from the EAT ECU memory. Only five
different faults can be stored in the memory at any one time. If a further fault occurs, the fault with the lowest priority
will be replaced by the new fault.
Mechanical limp home
In the mechanical limp home mode, gear engagement is controlled by the manual valve. The gearbox is fixed in 4th
gear if the fault occurs while the vehicle is moving, or 3rd gear if the fault occurs while the vehicle is stationary. 3rd
gear is also engaged if a vehicle is brought to a stop and the selector lever is moved out of, and back into, D. Neutral
and reverse gear are also available.
Fault effects and warning indications
Fault code,
OBD II
(TestBook)
Fault description
Effect
Warning lamp
illumination
MIL
Sport/
Manual
P0705
(14, 23)
* Gear position switch,
incorrect outputs
Maintains current gear in low range, limp home
mode in high range. Shift pressure to maximum,
harsh gear shifts/engagement.
On On
P0721
(21)
* Downshift safety
monitor prevented
downshift which would
have caused engine
overspeed
Maintains current gear in low range, limp home
mode in high range. Shift pressure to maximum,
harsh gear shifts/engagement.
On
On
P0722
(22)
* Torque converter
slipping
Maintains current gear in low range, limp home
mode in high range. Shift pressure to maximum,
harsh gear shifts/engagement.
On
On
P0731
(29)
* Ratio monitoring,
implausible 1st gear ratio
No apparent effect
On
On
P0732
(30)
* Ratio monitoring,
implausible 2nd gear
ratio
No apparent effect
On
Off
P0733
(31)
* Ratio monitoring,
implausible 3rd gear
ratio
No apparent effect
On
Off
P0734
(32)
* Ratio monitoring,
implausible 4th gear ratio
No apparent effect
On
Off
P0741
(5)
* Torque converter lock-
up clutch fault
May affect driveability.
On
Off
P0743
(7, 25)
* Torque converter lock-
up solenoid (MV 3), open
or short circuit
Limp home mode in low and high ranges. Shift
pressure to maximum, harsh gear shifts/
engagement.
On
On
P0748
(10, 28)
* Pressure regulating
solenoid (MV 4), open or
short circuit
Limp home mode in low and high ranges. Shift
pressure to maximum, harsh gear shifts/
engagement.
On
On
P0753
(8, 26)
* Shift solenoid (MV 1),
open or short circuit
Limp home mode in low and high ranges. Shift
pressure to maximum, harsh gear shifts/
engagement.
On
On
P0758
(9, 27)
* Shift solenoid (MV 2),
open or short circuit
Limp home mode in low and high ranges. Shift
pressure to maximum, harsh gear shifts/
engagement.
On
On
P1562
(24)
* Battery supply below
9V while engine running
Maintains current gear in low range, limp home
mode in range. Shift pressure to maximum, harsh
gear shifts/engagement.
Off
On