Range Rover Automatic Transmission. Manual - part 6

 

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Range Rover Automatic Transmission. Manual - part 6

 

 

1-13

Operation Pride

REPAIR

Check the gear position on the PRNDL, message center and from the gearbox diagnostic in the
real time monitor section on TestBook.
Verify they all return the same information as the lever is moved through all possible combinations.
Check mechanical selector for correct positioning.

CODE: 40 FGANG1, First gear ratio incorrect (97 MY onwards)

EFFECT: Limp home in third or fourth

DESCRIPTION

During normal operation, the TCM will monitor the input speed and output speed to determine if
the transmission is operating in the gear selected. The TCM will compare the ratio between the
calculated input speed and the output speed with the value for first gear stored in ROM. If this val-
ue is incorrect, the TCM will store code 40 for a first gear ratio fault.

CAUSE

Selected transmission gear has an incorrect ratio compared to its known value. See mechanical
diagnosis.
Incorrect input/output shaft speeds being sensed.

REPAIR

Transmission may need replacing.
Check input/output speed signals for correct operation.

CODE: 41 FGANG2, Second gear ratio incorrect (97 MY onwards)

EFFECT: Limp home in third or fourth

DESCRIPTION

During normal operation, the TCM will monitor the input speed and output speed to determine if
the transmission is operating in the gear selected. The TCM will compare the ratio between the
calculated input speed and the output speed with the value for second gear stored in ROM. If this
value is incorrect, the TCM will store code 41 for a second gear ratio fault.

CAUSE

Selected transmission gear has an incorrect ratio compared to its known value. See mechanical
diagnosis.
Incorrect input/output shaft speeds being sensed.

REPAIR

Transmission may need replacing.
Check input/output speed signals for correct operation.

1-13

Operation Pride

CODE: 42 FGANG3, Third gear ratio incorrect (97 MY Onwards)

EFFECT: Limp home in third or fourth

DESCRIPTION

During normal operation, the TCM will monitor the input speed and output speed to determine if
the transmission is operating in the gear selected. The TCM will compare the ratio between the
calculated input speed and the output speed with the value for third gear stored in ROM. If this
value is incorrect, the TCM will store code 42 for a third gear ratio fault.

CAUSE
Selected transmission gear has an incorrect ratio compared to its known value. See mechanical
diagnosis.
Incorrect input/output shaft speeds being sensed.

REPAIR
Transmission may need replacing.
Check input/output speed signals for correct operation.

CODE: 43 FGANG4, Fourth gear ratio incorrect (97 MY onwards)

EFFECT: Limp home in third or fourth
DESCRIPTION

During normal operation, the TCM will monitor the input speed and output speed to determine if
the transmission is operating in the gear selected. The TCM will compare the ratio between the
calculated input speed and the output speed with the value for fourth gear stored in ROM. If this
value is incorrect, the TCM will store code 43 for a fourth gear ratio fault.

CAUSE
Selected transmission gear has an incorrect ratio compared to its known value. See mechanical
diagnosis.
Incorrect input/output shaft speeds being sensed.

REPAIR
Transmission may need replacing.
Check input/output speed signals for correct operation.

CODE: 44 FWK, TCC gear ratio incorrect (97 MY onwards)

EFFECT: Limp home in third or fourth
At predetermined speeds, the TCM will lock the converter clutch via the TCC solenoid; this occurs
in third and fourth gears thereby giving a direct drive through the transmission. Once the convert-
er is locked up, the TCM will compare the input speed and output speed of the transmission and
verify if the gear ratio is the same as the one stored internally. If not, the TCM will store code 44.

1-13

Operation Pride

Automatic  Transmission Diagnostics - Electrical Symptoms
Model: 1995-97 Range Rover

CAUSE
TCC is not operating mechanically or has insu

fficient pressure to actuate. See mechanical diagn

o-

sis.
Incorrect input/output shaft speeds being sensed.

REPAIR
Transmission may need replacing.
Check input/output speed signals for correct operation.

TRANSFER BOX CONTROL UNIT (TCU) INDICATES LOW RANGE 
PERMANENTLY

EFFECT: No sports mode, shifts rough

DESCRIPTION

TCM assumes that low range is selected permanentl

y. Shifting to low range does not alter the

TCM’s shifting behavio r, i.e. economy mode has di fferent shift pattern and sport mode would be
manual mode.

CAUSE

TCU failure causing open circuit fault on the input to the TCM for range selected.

REPAIR

If the shift into low range does not take place, check TCU Connector C603 pin 35 and TCM con-
nector C601 pin 46 for 0V in high range and greater than 10V when in low range. Check the TCU
for signs of overheating or a burning smell, if evident replace the TCU. Make sure the motor is in
good condition before powering up with the new TCU as a failed motor will damage the new TCU.

TRANSFER BOX CONTROL UNIT (TCU) INDICATES HIGH RANGE 
PERMANENTLY

EFFECT: No manual mode in low range

DESCRIPTION

TCM assumes that high range is selected permanentl

y. Shifting to low range does not alter the

TCM’s shifting behavio r, i.e. economy mode has di fferent shift pattern and manual mode would be
sport mode.

CAUSE

TCU failure causing short to ground fault on the input to the TCM for range selected.

1-13

Operation Pride

REPAIR

If the shift into low range does not take place, check TCU connector C603 pin 35 and TCM con-
nector C601 pin 46 for 0V in high range and greater than 10V when in low range. Check the TCU
for signs of overheating or a burning smell. If evident, replace the TCU. Make sure the motor is in
good condition before powering up with the new TCU as a failed motor will damage the new TCU.

GEMS P1775 code

EFFECT: “CHECK ENGINE” light on

DESCRIPTION

This code confirms the existence of a stored TCM fault code.
The fault is flagged when the Pulse Width Modulation (PWM) signal on the ignition retard line has
a duty cycle of between 10% and 14% for 100 ms or longer.

CAUSE

If the fault is permanent and not intermittent, then the ignition retard value can be viewed by Test-
Book through the Real Time Monitoring section under the Switches and Status icon. A normal val-
ue of 17% should be shown if the fault is not present at the time of viewing. A value of 10% - 14%,
for example 12%, would indicate that the TCM fault is currently present.

REPAIR

Diagnose the TCM, retrieve the fault codes and follow the diagnosis for the stored faults.

GEMS P1776 code

EFFECT: “CHECK ENGINE” light on

DESCRIPTION

The ignition retard line from the ECM to the TCM will have a PWM signal to identify any ignition
retard requests during normal operation of the TCM.
The values for this signal are:



17% to indicate ignition retard is not active.



20% to 90% to indicate 0 to 27.8 retard.

CAUSE

During normal operation if the ignition retard request exceeds 4 seconds, then P1776 will be
flagged.
This can also be caused by a variety of electrical connector/terminal problems between the ECM
and TCM.

 

 

 

 

 

 

 

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