AT-36
TROUBLE DIAGNOSIS
How to Perform Trouble Diagnoses for Quick and Accurate RepairBCS000ZZ
INTRODUCTION
The TCM receives a signal from the vehicle speed sensor, accelera-
tor pedal position sensor or PNP switch and provides shift control or
lock-up control via A/T solenoid valves.
Input and output signals must always be correct and stable in the
operation of the A/T system. The A/T system must be in good oper-
ating condition and be free of valve seizure, solenoid valve malfunc-
tion, etc.
It is much more difficult to diagnose a malfunction that occurs inter-
mittently rather than continuously. Most intermittent malfunctions are
caused by poor electric connections or improper wiring. In this case,
careful checking of suspected circuits may help prevent the replace-
ment of good parts.
A visual check only, may not find the cause of the malfunctions. A
road test with CONSULT-II or a circuit tester connected should be
performed. Follow the AT- 3 7 , "
WORK FLOW" .
Before undertaking actual checks, take a few minutes to talk with a
customer who approaches with a drivability complaint. The customer
can supply good information about such malfunctions, especially
intermittent ones. Find out what symptoms are present and under
what conditions they occur. A “DIAGNOSTIC WORKSHEET” like the
example (AT- 3 8 , "
DIAGNOSTIC WORKSHEET" ) should be used.
Start your diagnosis by looking for “conventional” malfunctions first.
This will help troubleshoot drivability malfunctions on an electroni-
cally controlled engine vehicle.
Also check related Service bulletins for information.
SAT631IA
SAT632I
SEF234G
AT-38
TROUBLE DIAGNOSIS
DIAGNOSTIC WORKSHEET
Information From Customer
KEY POINTS
WHAT..... Vehicle & A/T models
WHEN..... Date, Frequencies
WHERE..... Road conditions
HOW..... Operating conditions, Symptoms
Customer name MR/MS Model & Year VIN
Trans. model Engine Mileage
Malfunction Date Manuf. Date In Service Date
Frequency❏ Continuous❏ Intermittent ( times a day)
Symptoms❏ Vehicle does not move. (❏ Any position❏ Particular position)
❏ No up-shift (❏ 1st → 2nd❏ 2nd → 3rd❏ 3rd → 4th)
❏ No down-shift (❏ 4th → 3rd❏ 3rd → 2nd❏ 2nd → 1st)
❏ Lock-up malfunction
❏ Shift point too high or too low.
❏ Shift shock or slip (❏ N → D❏ Lock-up❏ Any drive position)
❏ Noise or vibration
❏ No kick down
❏ No pattern select
❏ Others
()
TROUBLE DIAGNOSIS
AT-39
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Diagnostic Worksheet
1.❏ Read the Fail-safe and listen to customer complaints.AT- 3 4, AT- 3 8
2.❏ Check A/T fluidAT- 1 4❏ Leakage (Follow specified procedure)
❏ Fluid condition
❏ Fluid level
3.❏ Perform “STALL TEST” and “LINE PRESSURE TEST”.AT- 4 3
,
AT- 4 6
❏ “STALL TEST” — Mark possible damaged components/others.
❏ Torque converter one-way clutch
❏ Reverse clutch
❏ Forward clutch
❏ Overrun clutch
❏ Forward one-way clutch❏ Low & reverse brake
❏ Low one-way clutch
❏ Engine
❏ Line pressure is low
❏ Clutches and brakes except high clutch and
brake band are OK
❏ “LINE PRESSURE TEST” — Suspected parts:
4.❏ Perform “Road Test”.AT- 4 8
4-1.“Check Before Engine is Started”AT- 4 8
❏ AT-173, "A/T CHECK Indicator Lamp Does Not Come On" .
❏ Perform self-diagnostics. Enter checks for detected items. AT- 6 9
, AT- 7 6 .
❏ AT-133, "
CAN COMMUNICATION LINE" .
❏ AT-80, "
VEHICLE SPEED SENSOR·A/T (REVOLUTION SENSOR)" .
❏ AT-86, "
VEHICLE SPEED SENSOR MTR" .
❏ AT-120, "
TURBINE REVOLUTION SENSOR" .
❏ AT-90, "
SHIFT SOLENOID VALVE A" .
❏ AT-95, "
SHIFT SOLENOID VALVE B" .
❏ AT-100, "
OVERRUN CLUTCH SOLENOID VALVE" .
❏ AT-105, "
TORQUE CONVERTER CLUTCH SOLENOID VALVE" .
❏ AT-110, "
BATT/FLUID TEMP SEN (A/T FLUID TEMP SENSOR CIRCUIT AND TCM POWER
SOURCE)" .
❏ AT-116, "
ENGINE SPEED SIGNAL" .
❏ AT-136, "
A/T 1ST GEAR FUNCTION" .
❏ AT-140, "
A/T 2ND GEAR FUNCTION" .
❏ AT-143, "
A/T 3RD GEAR FUNCTION" .
❏ AT-146, "
A/T 4TH GEAR FUNCTION" .
❏ AT-151, "
A/T TCC S/V FUNCTION (LOCK-UP)" .
❏ AT-126, "
LINE PRESSURE SOLENOID VALVE" .
❏ AT-156, "
CONTROL UNIT (RAM)" .
❏ AT-157, "
CONTROL UNIT (ROM)" .
4-2.“Check at Idle”AT- 4 8
❏ AT-175, "Engine Cannot Be Started in “P” and “N” Position" .
❏ AT-176, "
In “P” Position, Vehicle Moves Forward or Backward When Pushed" .
❏ AT-176, "
In “N” Position, Vehicle Moves" .
❏ AT-177, "
Large Shock. “N” → “R” Position" .
❏ AT-179, "
Vehicle Does Not Creep Backward in “R” Position" .
❏ AT-181, "
Vehicle Does Not Creep Forward in “D”, “3”, “2” or “1” Position" .
AT-40
TROUBLE DIAGNOSIS
4. 4-3.“Cruise Test”AT- 5 0
Part 1
❏ AT-182, "
Vehicle Cannot Be Started From D1" .
❏ AT-184, "
A/T Does Not Shift: D1 → D2 or Does Not Kickdown: D4 → D2" .
❏ AT-186, "
A/T Does Not Shift: D2 → D3" .
❏ AT-188, "
A/T Does Not Shift: D3 → D4" .
❏ AT-191, "
A/T Does Not Perform Lock-up" .
❏ AT-193, "
A/T Does Not Hold Lock-up Condition" .
❏ AT-195, "
Lock-up Is Not Released" .
❏ AT-195, "
Engine Speed Does Not Return To Idle (Light Braking D4 → D3 )" .
Part 2AT- 5 1
❏ AT-182, "Vehicle Cannot Be Started From D1" .
❏ AT- 1 8 4 , "
A/T Does Not Shift: D1 → D2 or Does Not Kickdown: D4 → D2" .
❏ AT-186, "
A/T Does Not Shift: D2 → D3" .
❏ AT-188, "
A/T Does Not Shift: D3 → D4" .
Part 3AT- 5 2
❏ AT-197, "A/T Does Not Shift: D4 → 33 , When A/T Selector Lever “D” → “3”" .
❏ AT-203, "
Vehicle Does Not Decelerate By Engine Brake (D4 → 33 )" .
❏ AT-198, "
A/T Does Not Shift: 33 → 22 , When Selector Lever “3” → “2” Position" .
❏ AT-205, "
Vehicle Does Not Decelerate By Engine Brake (33 → 22 )" .
❏ AT-200, "
A/T Does Not Shift: 22 → 11 , When Selector Lever “2” → “1” Position" .
❏ AT-208, "
Vehicle Does Not Decelerate By Engine Brake (22 → 11 )" .
❏ Perform self-diagnostics. Enter checks for detected items. AT- 6 9
, AT- 7 6 .
❏ AT-133, "
CAN COMMUNICATION LINE" .
❏ AT-80, "
VEHICLE SPEED SENSOR·A/T (REVOLUTION SENSOR)" .
❏ AT-86, "
VEHICLE SPEED SENSOR MTR" .
❏ AT-120, "
TURBINE REVOLUTION SENSOR" .
❏ AT-90, "
SHIFT SOLENOID VALVE A" .
❏ AT-95, "
SHIFT SOLENOID VALVE B" .
❏ AT-100, "
OVERRUN CLUTCH SOLENOID VALVE" .
❏ AT-105, "
TORQUE CONVERTER CLUTCH SOLENOID VALVE" .
❏ AT-110, "
BATT/FLUID TEMP SEN (A/T FLUID TEMP SENSOR CIRCUIT AND TCM POWER
SOURCE)" .
❏ AT-116, "
ENGINE SPEED SIGNAL" .
❏ AT-136, "
A/T 1ST GEAR FUNCTION" .
❏ AT-140, "
A/T 2ND GEAR FUNCTION" .
❏ AT-143, "
A/T 3RD GEAR FUNCTION" .
❏ AT-146, "
A/T 4TH GEAR FUNCTION" .
❏ AT-151, "
A/T TCC S/V FUNCTION (LOCK-UP)" .
❏ AT-126, "
LINE PRESSURE SOLENOID VALVE" .
❏ AT-156, "
CONTROL UNIT (RAM)" .
❏ AT-157, "
CONTROL UNIT (ROM)" .
5.❏ For self-diagnosis NG items, inspect each component. Repair or replace the damaged parts.
6.❏ Perform “Road Test”.AT- 4 8
7.❏ Perform the Diagnostic Procedures for all remaining items marked NG. Repair or replace the damaged parts.
Refer to the Symptom Chart when you perform the procedures. (The chart also shows some other possible
symptoms and the component inspection orders.)AT- 5 5
8.❏ Erase DTC from TCM and ECM memories.AT- 6 9AT- 7 9
TROUBLE DIAGNOSIS
AT-43
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Inspections Before Trouble DiagnosisBCS00102
A/T FLUID CHECK
Fluid Leakage and Fluid Level Check
Inspect for A/T fluid leakage and check the A/T fluid level. Refer to AT- 1 4 , "Checking A/T Fluid" .
A/T Fluid Condition Check
Inspect the A/T fluid condition.
STALL TEST
Stall Test Procedure
1. Check ATF and engine oil levels. If necessary, add ATF and oil.
2. Drive vehicle for approximately 10 minutes or until ATF and
engine oil reach operating temperature.
3. Set parking brake and block wheels.
4. Install a tachometer where it can be seen by driver during test.
It is good practice to mark the point of specified engine
rpm on indicator.
5. Start engine, apply foot brake, and place selector lever in “D”
position.
Fluid status Conceivable Cause Required Operation
Varnished (viscous
varnish state)Clutch, brake
scorchedReplace the ATF and check the A/T
main unit and the vehicle for mal-
functions (wire harnesses, cooler
pipes, etc.)
Milky white or
cloudyWater in the ATFReplace the ATF and check for
places where water is getting in.
Large amount of
metal powder mixed
inUnusual wear of
sliding parts within
A/TReplace the ATF and check for
improper operation of the A/T.
SAT638A
ATF operating temperature: 50 - 80°C (122 - 176°F)
SAT647B
SCIA7463E
SCIA5703E
AT-44
TROUBLE DIAGNOSIS
6. Accelerate to wide open throttle gradually while applying foot
brake.
7. Quickly note the engine stall revolution and immediately release
throttle.
CAUTION:
Do not hold down the accelerator pedal for more than 5 sec-
onds during this test.
8. Move selector lever to “N” position.
9. Cool off ATF.
CAUTION:
Run engine at idle for at leas 1 minute.
10. Repeat steps 6 through 9 with selector lever in “3”, “2”, “1” and
“R” positions.
Judgement of Stall Test
The test result and possible damaged components relating to each result are shown in the illustrations on next
page.
In order to pinpoint the possible damaged components, refer to AT- 3 7 , "
Work Flow Chart" .
NOTE:
Stall revolution is too high in “D”, “3”, “2”, or “1” position:
Slippage occurs in 1st gear but not in 2nd and 3rd gears. ..... Low one-way clutch slippage
Slippage occurs in the following gears:
1st through 3rd gears in “D” position and engine brake functions with selector lever set to “3” position.
1st and 2nd gears in “2” position and engine brake functions with accelerator pedal released (fully closed
throttle)...... Forward clutch or forward one-way clutch slippage
Stall revolution is too high in “R” position:
Engine brake does not function in “1” position. ..... Low & reverse brake slippage
Engine brake functions in “1” position. ..... Reverse clutch slippage
Stall revolution within specifications:
Vehicle does not achieve speed of more than 80 km/h (50 MPH). ..... One-way clutch seizure in torque
converter housing
CAUTION:
Be careful since automatic fluid temperature increases abnormally.
Slippage occurs in 3rd and 4th gears in “D” position. ..... High clutch slippage
Slippage occurs in 2nd and 4th gear in “D” position. ..... Brake band slippage
Engine brake does not function in 2nd and 3rd gears in “D” position with 3rd position switch set to ON, 2nd
gear in “2” position, and 1st gear in “1” position. ..... Overrun clutch slippage
Stall revolution less than specifications:
Poor acceleration during starts. ..... One-way clutch seizure in torque converterStall revolution
For QR20DE engine models:
2,400 - 2,850 rpm
For VQ23DE engine models:
2,400 - 2,900 rpm
SAT514G
SCIA5704E
AT-46
TROUBLE DIAGNOSIS
LINE PRESSURE TEST
Line Pressure Test Ports
Location of line pressure test ports are shown in the figure.
Always replace pressure plugs as they are self-sealing
bolts.
Line Pressure Test Procedure
1. Check ATF and engine oil levels. If necessary, add ATF or
engine oil.
2. Drive vehicle for approx. 10 minutes or until engine oil and ATF
reach operating temperature.
3. Install oil pressure gauge to corresponding line pressure test
port.
4. Set parking brake and block wheels.
SCIA3332E
ATF operating temperature: 50 - 80°C (122 -176°F)
SAT647B
SCIA4845E
SCIA7463E
TROUBLE DIAGNOSIS
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5. Start engine and measure line pressure at idle and stall speed.
CAUTION:
Keep the brake pedal pressed all the way down during
measurement.
When measuring line pressure at stall speed, refer to AT-
43, "STALL TEST" .
Line Pressure
Judgement of Line Pressure Test
SAT493G
Engine speed rpmLine pressure kPa (bar, kg/cm2 , psi)
“D”, “3”, “2” and “1” positions “R” position
Idle 500 (5.00, 5.1, 73) 778 (7.78, 7.9, 113)
Stall 1,233 (12.33, 12.6, 179) 1,918 (19.18, 19.6, 278)
Judgement Suspected parts
At idleLine pressure is low in all positions.
Oil pump wear
Control piston damage
Pressure regulator valve or plug sticking
Spring for pressure regulator valve damaged
Fluid pressure leakage between oil strainer and pressure regulator valve
Clogged strainer
Line pressure is low in particular posi-
tion.
Fluid pressure leakage between manual valve and particular clutch
For example, line pressure is:
− Low in “R” and “1” positions, but
− Normal in “D”, “3” and “2” positions.
Therefore, fluid leakage exists at or around low and reverse brake circuit.
Refer to AT-18, "
CLUTCH AND BAND CHART" .
Line pressure is high.
Accelerator pedal position signal malfunction
A/T fluid temperature sensor damaged
Line pressure solenoid valve sticking
Short circuit of line pressure solenoid valve circuit
Pressure modifier valve sticking
Pressure regulator valve or plug sticking
Open in dropping resistor circuit
At stall
speedLine pressure is low.
Accelerator pedal position signal malfunction
Line pressure solenoid valve sticking
Short circuit of line pressure solenoid valve circuit
Pressure regulator valve or plug sticking
Pressure modifier valve sticking
Pilot valve sticking