Range Rover Automatic Transmission. Manual - part 5

 

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Range Rover Automatic Transmission. Manual - part 5

 

 

1-13

Operation Pride

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

CAUSE

Signal from TCM to ECM being sent for too long or outside normal limits.

REPAIR

Check the following connectors for any sign of loose connectors or terminals backing out.

ECM connector C507 pin 31.

TCM connector C601 pin 32.

In-line connectors C551 pin 4 and C659 pin 9.

CODE: 24 FRSS, Output speed sensor, signal out of range

EFFECT: Limp home in third or fourth

DESCRIPTION

This fault is only tested during a downshift and therefore the engine must be in a forward gear, i.e.
D, 3, 2. If the engine speed is above a defined threshold during the shift for a duration of 50 ms or
more, then the fault will flagged.
Erratic, harsh, or elongated shifts can be a result of this fault.

CAUSE

The output speed sensor provides the information necessary for the TCM to calculate the pressure
needed for any shift and also for the length of the shift. The TCM compares the engine speed to
output speed for a measure of slip.
Mechanical slip due to excessive internal wear on the clutches can also cause a large difference
between engine speed input and output speed.

REPAIR
Check the continuity of the wiring from the TCM to the transmission connector and also the resis-
tance of the output speed sensor.
See figure 1 for assistance with the transmission connector pinouts and resistance of the output
speed sensor.
Verify the mechanical condition of the transmission and check transmission fluid for contamination.

CODE: 26 FT_T, Engine torque signal out of range

EFFECT: Poor shift quality - Maximum pressure on shifts
DESCRIPTION

The ECM provides the TCM with an indication of the torque the engine is currently producing. In-
correct information can affect both the timing and the length of the shifts. The torque signal is also
needed to determine the amount of torque reduction required by the TCM for smooth shifts.
Erratic, harsh or elongated shifts can result.

1-13

Operation Pride

CAUSE
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.
This line will also indicate a fault condition when the TCM sends a PWM of less than 10% or
greater than 93% and the engine speed is above 448 rpm

REPAIR
Check the following connectors for any sign of loose connectors or terminals backing out.



ECM connector C505 pin 29.



TCM connector C601 pin 21.



In-line connectors C551 pin 5 and C659 pin 1.

CODE: 27 FFSTBR, Output speed sensor, no signal

EFFECT: Limp home in third or fourth
DESCRIPTION

By comparing the engine speed while in gear and checking for the signal from the output speed
sensor, it can be determined if the sensor is operational. The diagnostic monitors for zero rpm from
the sensor while the engine speed is above 2000 rpm and a forward gear is selected. If the fault
condition lasts for 50 ms, then the fault will be flagged.
The engine speed and torque are used by the TCM to determine input shaft speed. When the
torque converter locks up, engine speed equals input speed.
Erratic, harsh or elongated shifts can result.

CAUSE
The output speed sensor provides the information necessary for the TCM to calculate the pressure
needed for any shift and also for the length of the shift. The TCM compares the engine speed to
output speed for a measure of slip. Mechanical slip due to excessive internal wear on the clutches
can also cause a large difference between engine speed input and output speed.

REPAIR
Check the continuity of the wiring from the TCM to the transmission connector and also the resis-
tance of the output speed sensor. Check output sensor screen wires for shorts to output sensor
wiring.
See figure 1 for assistance with the transmission connector pinouts and resistance of the output
speed sensor. Verify the mechanical condition of the transmission and check transmission fluid for
contamination.

1-13

Operation Pride

CODE: 28 FEPROM, TCM data corrupted

EFFECT: Limp home in third or fourth

DESCRIPTION

On each power-up the TCM analyzes its internal Read Only Memory (ROM) and checks that its
contents are correct by calculating the contents for a specified length and comparing this value
with the checksum value stored in ROM. When the two disagree on three attempts, the TCM will
flag a code 28. The ROM contains the program which runs the TCM and calculates the upshift
and downshift points together with all the diagnostics on the TCM and its associated sensors.
The TCM will also analyze its Electrically Erasable Programmable Read Only Memory (EEPROM),
which is an area of memory that is kept alive even when the TCM is disconnected. This memory
is used to determine that the stored conditions of freeze frame and DTCs are correct.
The same conditions apply for flagging a fault in the EEPROM as in the ROM.

CAUSE

The TCM data has become corrupted and the information it contains cannot be relied upon.

REPAIR

Renew the TCM and verify everything works correctly.

CODE: 30 FPOS, Gear position switch inaccurate while running

EFFECT: Limp home in third or fourth

DESCRIPTION

During normal operation the gear position is read from the XYZ switches. This information is also
read by the BeCM so it can enable/disable cranking and display the currently selected gear on the
message center.
If the lever position does not return the correct selection then the BeCM, TCM and  H-GATE will re-
ceive incorrect information.
If the wiring between the XYZ switches and the TCM is good but the wiring between the XYZ
switches and the BeCM or H-GATE is faulty, no fault code woud set but a gear indication problem
would exist.
The table on the following page helps to identify the reaction of the BeCM, TCM and H-GATE to
false information from the XYZ switches.
The first column is the reaction to the system when Park is selected, the second when Reverse is
selected and so on.

1-13

Operation Pride

ÁÁÁÁÁÁÁ

Status

ÁÁÁÁÁ

P

ÁÁÁÁÁ

R

ÁÁÁÁÁ

N

ÁÁÁÁÁ

D

ÁÁÁÁÁ

3

ÁÁÁÁÁ

2

ÁÁÁÁÁ

1

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

Normal

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

R

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

D

ÁÁÁÁÁ

ÁÁÁÁÁ

3

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

X o/c

ÁÁÁÁÁ

ÁÁÁÁÁ

Z

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

D

ÁÁÁÁÁ

ÁÁÁÁÁ

D

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

Y o/c

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

Z

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

Z o/c

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

R

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

R

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

Z

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

X s/c gnd

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

R

ÁÁÁÁÁ

ÁÁÁÁÁ

R

ÁÁÁÁÁ

ÁÁÁÁÁ

3

ÁÁÁÁÁ

ÁÁÁÁÁ

3

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁÁÁ

Y s/c gnd

ÁÁÁÁÁ

R

ÁÁÁÁÁ

R

ÁÁÁÁÁ

N

ÁÁÁÁÁ

D

ÁÁÁÁÁ

3

ÁÁÁÁÁ

3

ÁÁÁÁÁ

D

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

Z s/c gnd

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

3

ÁÁÁÁÁ

ÁÁÁÁÁ

D

ÁÁÁÁÁ

ÁÁÁÁÁ

D

ÁÁÁÁÁ

ÁÁÁÁÁ

3

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

X s/c bat

ÁÁÁÁÁ

ÁÁÁÁÁ

Z

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

D

ÁÁÁÁÁ

ÁÁÁÁÁ

D

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

Y s/c bat

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

Z

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

2

ÁÁÁÁÁ

ÁÁÁÁÁ

1

ÁÁÁÁÁÁÁ

ÁÁÁÁÁÁÁ

Z s/c bat

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

R

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

N

ÁÁÁÁÁ

ÁÁÁÁÁ

R

ÁÁÁÁÁ

ÁÁÁÁÁ

P

ÁÁÁÁÁ

ÁÁÁÁÁ

Z

Note: Bold selections indicate a failure condition, Z is an open circuit condition on all switch

positions and is not normally seen.

The TCM will store fault 30 when a fault condition has been seen for more than 50 ms.

CAUSE

The status information from the XYZ switches is incorrect due to either an open circuit switch or
shorts in the wiring from the switches.
A misadjusted mechanical selector can cause the switch position to be different from the mechan-
ically selected position.

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: 31 FPOSST, Gear position switch inaccurate while starting

EFFECT: Limp home in third or fourth

DESCRIPTION

During normal operation the gear position is read from the XYZ switches. This information is also
read by the BeCM so it can enable/disable cranking and display the currently selected gear on the
message center.
The TCM will check the probability of this fault once only during cranking, when the engine speed
exceeds a specific threshold (96 rpm). If during this time the TCM detects anything other than
Park or Neutral for more than 50 ms, then a fault code 31 will be stored.

CAUSE

The status information from the XYZ switches is incorrect due to either an open circuit switch, or
shorts on the wiring from the switches.
A misadjusted mechanical selector can cause the switch position to be different from the mechan-
ically selected position.

 

 

 

 

 

 

 

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