Lexus SC300 / Lexus SC400. Manual - part 99

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AT00X–01

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

SHIFT LOCK SYSTEM

TROUBLESHOOTING

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

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HOW TO PROCEED WITH TROUBLESHOOTING

AT09N–0D

1. 

CUSTOMER PROBLEM ANALYSIS
Using the customer problem analysis check sheet for reference, ask the customer in as much detail as
possible about the problem.

2. 

CHECK AND CLEAR THE DIAGNOSTIC TROUBLE CODES (PRECHECK)
Before confirming the problem symptom, first check if there are any diagnostic trouble malfunction codes
stored in memory. When there are malfunction codes, make a note of them, then clear them and proceed
to “3. Problem Symptom Confirmation”.

3. PROBLEM 

SYMPTOM 

CONFIRMATION

Confirm the problem symptoms.

4. SYMPTOM 

SIMULATION

If the problem does not reappear, be sure to simulate the problem by mainly checking the circuits indicated
by the diagnostic trouble code in step 2., using “Problem Simulation method”.

5. 

DIAGNOSTIC TROUBLE CODE CHECK
Check the diagnostic trouble codes. Check if there is abnormality in the sensors or the wire harness.
If a malfunction code is output, proceed to “6. Diagnostic Trouble Code Chart”.
If the normal code is output, proceed to “11. Matrix Chart of Problem Symptoms”.
Be sure to proceed to “6. Diagnostic Trouble Code Chart” after the steps 2. and 3. are completed.
If troubleshooting is attempted only by following the malfunction code stored in the memory is output, errors
could be made in the diagnosis.

6. 

DIAGNOSTIC TROUBLE CODE CHART
If a malfunction code is confirmed in the diagnostic trouble code check, proceed to the inspection proce-
dure indicated by the matrix chart for each diagnostic trouble code.

7. PRELIMINARY 

CHECK

Carry out a preliminary check of the transmission oil level, throttle cable adjustment, etc.

8. 

SHIFT POSITION SIGNAL CHECK
Carry out the shift position signal check when the transmission gears do not up–shift, down–shift or lock–
up. This is to check the output condition from the ECM to each solenoid. If the results are NG, then it is
likely that the trouble is in the electrical system (particularly in the sensors or the ECM).
Proceed to Part 1 (Electrical System) under “11. Matrix Chart of Problem Symptoms”. If all the circuits speci-
fied in Part 1 are OK, check the ECM and replace it.

9. 

MECHANICAL SYSTEM TEST
(Stall Test, Time Lag Test, Line Pressure Test, Accumulator Back Pressure Test)
If the malfunction is found in the stall test, time lag test, line pressure test or accumulator back pressure
test, check the parts indicated in the respective tests. If the problem is that “shift shock is large”, perform
the accumulator back pressure test.

10.  MANUAL SHIFTING TEST

If the results of the manual driving test are NG, it is likely that the trouble is in the mechanical system or
hydraulic system. Proceed to Part 2 (Mechanical System) under the Matrix Chart of Problem Symptoms.

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

11.  MATRIX CHART OF PROBLEM SYMPTOMS

If the normal code is confirmed in the diagnostic trouble code check, perform inspection according to the
inspection order in the matrix chart of problem symptoms. Perform diagnosis of each circuit or part in the
order shown in the Matrix Chart. The Matrix Chart contains 3 chapters, Electronically Controlled Circuits
in Chapter 1, On–vehicle Inspection in Chapter 2 and Off–vehicle Inspection in Chapter 3. If all the circuits
indicated in Chapter 1 are normal, proceed to Chapter 2. If all the parts indicated in Chapter 2 are normal,
proceed to Chapter 3. If all the circuits and parts in Chapter 1–Chapter 3 are normal and the trouble still
occurs, check and replace the ECM.

12. CIRCUIT 

INSPECTION

Perform diagnosis of each circuit in accordance with the inspection order confirmed in 6. and 11. Judge
whether the cause of the problem is in the sensor, actuators, wire harness and connectors, or the ECM.
In some cases, the Flow Chart instructs that a throttle signal check, brake signal check or kick down signal
check (in test mode) be performed. These are diagnosis functions used to check if signals are being input
correctly to the ECM.

13. PARTS INSPECTION

Check the individual parts of the mechanical system and hydraulic system in the order of the numbers indi-
cated in the Matrix Chart.

14. REPAIRS

After the cause of the problem is located, perform repairs by following the inspection and replacement pro-
cedures in this manual or ’94 A340E and A341E Automatic Transmission Repair Manual (for LEXUS
SC400).

15. CONFIRMATION TEST

After completing repairs, confirm not only that the malfunction is eliminated, but also conduct a test drive,
etc., to make sure the entire electronically controlled transmission system is operating correctly.

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A304E (1UZ–FE) AUTOMATIC TRANSMISSION

TROUBLESHOOTING

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