Flow of Diagnosis

HOW TO PROCEED WITH TROUBLESHOOTING
The Transaxle Control System broadly consists of the sensors, Engine Control Module (ECM) and actuators. The ECM receives signals from various sensors, judges the operating conditions and determines the shift and lock-up timing. When troubleshooting OBD II vehicles, use an OBD II Scan Tool complying with SAE J1978 or LEXUS hand-held tester to confirm the diagnostic trouble codes, freeze frame data and engine data. This will enable you to determine the system causing the problem. This section the best method of troubleshooting and how to carry out the necessary repairs.

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. CONNECT THE OBD II SCAN TOOL OR LEXUS HAND-HELD TESTER TO DLC3
Connect the OBD II scan tool complying with SAE J1978 or LEXUS hand-held tester to the vehicle's data link connector 3.

NOTICE: For OBD II scan tool or LEXUS hand-held tester operating instructions, see the instruction booklet accompanying the scan tool.

If your display shows "UNABLE TO CONNECT TO VEHICLE" when you have you have connected the scan tool/LEXUS hand-held tester cable to DLC3, turned the ignition switch ON and operated the scan tool/LEXUS hand-held tester, inspect DLC3.

3. CHECK DIAGNOSTIC TROUBLE CODE AND FREEZE FRAME DATA (PRECHECK)
First check the diagnostic trouble codes. If a code is output, make a note of it. Also check and note the freeze frame data.

HINT: Output of the malfunction code indicates a circuit malfunction. However, it does not indicate whether the malfunction is still occurring or occurred in the past and returned to normal. To determine this, first confirm the problem symptoms in Step 7 and then recheck the diagnostic trouble code in Step 9. If troubleshooting has begun based only on the malfunction code in the diagnostic trouble code check in Step 3, it could result in a misdiagnosis and troubleshooting of circuits which are normal, making it more difficult to locate the cause of the problem.

4. CLEAR DIAGNOSTIC TROUBLE CODE AND FREEZE FRAME DATA
Use the OBD II scan tool or LEXUS hand-held tester to erase the diagnostic trouble codes and freeze frame data.

NOTICE: For OBD II scan tool or LEXUS hand-held tester operating instructions, see the instruction booklet accompanying the scan tool.

5. VISUAL INSPECTION

6. SETTING THE CHECK MODE DIAGNOSIS

7. PROBLEM SYMPTOM CONFIRMATION
Confirm the problem symptoms.

8. 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 3, using "Problem Simulation method".

9. 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 "9 Diagnostic Trouble Code Chart". If the normal code is output, proceed to "14 Matrix Chart of Problem Symptoms". Be sure to proceed to "9 Diagnostic Trouble Code Chart" after the steps 3 to 6 inclusive 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.

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

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

12. MECHANICAL SYSTEM TEST (Stall Test, Time Lag Test, Line Pressure Test)
If the malfunction is found in the stall test, time lag test or line pressure test, check the parts indicated in the respective tests.

13. 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.

14. 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.

15. CIRCUIT INSPECTION
Perform diagnosis of each circuit in accordance with the inspection order confirmed in Steps 9 and 13. 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 or brake signal check be performed. These are diagnosis functions used to check if signals are being input correctly to the ECM.

16. PARTS INSPECTION
Check the individual parts of the mechanical system and hydraulic system in the order of the numbers indicated in the Matrix Chart.

17. REPAIRS
After the cause of the problem is located, perform repairs by following the inspection and replacement procedures.

18. CONFIRMATION TEST
After completing adjustment or repairs, confirm not only that the malfunction is eliminated, but also conduct a test drive, etc., to make sure the entire Engine Control System is operating normally.