Page 39 of 74

ZF Automatic Transmissions Service Manual
Problem Possible Cause
1.3.6 Fault Finding Chart
Action
Converter
Stall speed too low
Stall speed too
high and keeps
rising
Acceleration below specification
Top speed below specification
Position 'P'- Park
Will not move out of Park
Does not engage Park
Does not hold
Starter motor does not operate
Position 'R- Reverse
No reverse gear or severely
delayed engagement
High pitched squeaking noise Stator freewheel
faulty allowing
stator to revolve
Engine out of tune
Transmission slip.
Engine out of tune
Torque converter freewheel faulty
allowing stator to revolve.
Engine out of tune.
Torque converter freewheel seized.
Engine out of tune.
Gearshift interlock failure
Parking pawl mechanism sticking
Check cable adjustment
Parking pawl mechanism damaged
Check cable adjustment
Starter
inhibit switch faulty.
Faulty selector lever.
Position
'P' or 'N' not selected.
Check cable adjustment
Dirty oil filter.
Jammed governor.
Jammed reverse inhibit valve.
Low oil level.
'B' clutch destroyed (also no 3rd
gear
in Drive).
'D' clutch destroyed.
'E' clutch destroyed (no engine
braking
in 2nd & 3rd gears.
Reverse gear safety valve faulty. Renew
torque converter
Check engine tune.
Check oil level, check mechanical
failure, renew transmission as
necessary.
Renew torque converter.
Check engine tune.
Renew torque converter.
Check engine tune.
Rectify. Renew fuse, check circuits,
renew relay and solenoid.
Renew park pawl components:
connecting bar, pawl
pin, tension
spring, guide piece
& guide sheet
Adjust cable as necessary.
Replace park pawl components
Adjust cable as necessary.
Replace switch.
Replace lever.
Select 'P'
or 'N'.
Adjust cable as necessary.
Renew oil filter.
Replace governor.
Replace valve block.
Check oil.
Service
/ renew transmission.
Service
/ renew transmission.
Service
/ renew transmission.
Service
/ renew valve block.
Issue 1 August 1994 34
Page 52 of 74

4
AFLR M- -1
4 13 9
14
15 7
J44-718
1.
Selector 2. Mode switch 3. Rotary switch
4. Transmission control unit 5. Output shaft speed sensor 6. Kick-down switch 7. Battery
8. Transmission relay
9.
10.
11.
12.
13.
14.
15.
16.
Transmission control module (TCM)
Reverse lamps
Start inhibiter
Engine speed
Ignition retard
Engine load
Engine control module
(ECM) Engine speed sensor
Fig.
1 Control Layout Schematic
2.1.5 Transmission Control Module (TCM)
The Transmission Control Module (TCM) is an electronic control unit located in the front passenger footwell behind
the underscuttle pad. It is electrically connected to the transmission and other components through a cable harness
and multiple pin plug.
The TCM continuously monitors the gear selected (via the rotary transmission switch), the speed of the output shaft
(by speed sensor on the output shaft) and throttle position ('kick
-down' switch). This information plus input from the
Engine Control Module (ECM) of throttle angle and engine speed and load in conjunction with a pre-programmed con- trol map, enables the most suitable gear to be selected.
The TCM, by operating solenoid valves
MVI, MV2 and MV3, controls the gear shift speed and in conjunction with the
solenoid operated pressure control valve, controls the gear shift quality. Gear shift quality on upshifts is improved by
the TCM momentarily retarding the ignition to reduce the torque input as the gear change takes place. Information
is fed to the TCM from sensors and
if any electronic component fails, the basic shift changes will be performed by the
hydro-mechanical system, ie Park, Reverse, Neutral, D3 or D4.
46
Issue 1 August 1994
Page 66 of 74

ZF Automatic Transmissions Service Manual
Problem Possible Cause
2.3.4 Road Test
. Fully check all shift speeds and note. Compare the results with the specification in addition to general observations of transmission behaviour, noises, leaks etc., and consult the following Fault Finding Chart.
Action
CAUTION:
When renewing the transmission, ALWAYS flush out the oil cooler and feed and return pipes.
2.3.5 Electrical Checks
. Check 'Kick-down'.
If any electrical component fault is suspected, refer to Electrical Diagnostic Manual (EDM) to verify the failure mode
before a repair or replacement is attempted.
2.3.6 Fault Finding Chart
Stall speed too low
Stall speed too high and keeps
,ising
hceleration below specification
Top speed below specification
'osition 'P - Park
Nil1 not move out of Park
Ioes not engage Park
Ioes not hold Stator
freewheel faulty allowing stator to
revolve
Engine out of tune
Transmission slip
Engine out of tune
Torque converter freewheel faulty
allowing stator to revolve.
'Kick
-down' switch defective.
Transmission
in 'Limp Home' mode
Engine out of tune
Torque converter freewheel seized
Engine out of tune
Gearshift interlock failure
Check cable adjustment
Parking pawl mechanism sticking
Check cable adjustment
Parking pawl mechanism damaged Renew
torque converter
Check engine tune
Check oil level, check mechanical
failure, renew transmission as
necessary
Check engine tune
Renew torque converter.
Refer to EDM, rectify
I renew
'Kick
-down'switch.
Check.
Check
engine tune
Renew torque converter
Check engine tune
Refer to EDM, rectify
- renew fuse,
check circuits, renew relay and
solenoid.
Check central
'P, check Park switch,
check Brake switch.
Adjust to correct setting
Renew park pawl components:
connecting bar, pawl pin, torsion
spring, pawl, guide piece and guide
sheet.
Adjust to correct setting
Replace park pawl components
61 Issue 1 August 1994