AUTOMATIC TRANSAXLE SYSTEM, Diagnostic DTC:P0746

DESCRIPTION

The ECM uses the vehicle speed signal and signals from the transmission speed sensors (NC, NT) to detect the actual gear (1st, 2nd, 3rd, 4th, 5th or 6th gear).

Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical problems of the shift solenoid valves and valve body.

MONITOR DESCRIPTION

The ECM commands gear shifts by turning the shift solenoid valves on and off. According to the input shaft speed, intermediate (counter) shaft speed and output shaft speed, the ECM detects the actual gear (1st, 2nd, 3rd, 4th, 5th or 6th gear). When the gear commanded by the ECM and the actual gear are not the same, the ECM illuminates the MIL and stores the DTC.

CAUTION / NOTICE / HINT

PROCEDURE

1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P0746)

   
   

   1. Connect the GTS to the DLC3.

   2. Turn the ignition switch to ON.

   3. Turn the GTS on.

   4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

      
      Powertrain > Engine and ECT > Trouble Codes

   5. Read the DTCs using the GTS.

      Result
      Result Proceed to Only P0746 is output A P0746 and other DTCs are output B

      Tech Tips

      If shift solenoid valve SL1 is stuck off, DTCs for several shift solenoid valves including the malfunctioning shift solenoid valve will be stored.

   
   

   A

   GO TO STEP 3 Click here

   B

2. PERFORM ACTIVE TEST USING GTS (DRIVING TEST)

   Note

   This test should always be performed with at least 2 people.

   
   

   1. Warm up the engine.

   2. Turn the ignition switch off.

   3. Connect the GTS to the DLC3.

   4. Turn the ignition switch to ON.

   5. Turn the GTS on.

   6. Enter the following menus: Powertrain / Engine and ECT / Active Test.

   7. According to the display on the GTS, perform the Active Test.

      Tech Tips

      
      

      • Comparing the gear commanded by the Active Test with the actual gear enables confirmation of the problem.

        Click here

      • The gear commanded by the ECM is shown in the Data List / Shift Status display on the GTS.

      
      Powertrain > Engine and ECT > Active Test

      Tester Display	Measurement Item	Control Range	Diagnostic Note
      Control the Shift Position	Operate the shift solenoid valves and set each shift position	Press "→" button: Shift up Press "←" button: Shift down	Can be used to check the operation of the shift solenoid valves. A 10-second interval is required between gear changes. Do not down-shift at high speeds. Doing so will damage the automatic transaxle. [Vehicle Condition] 50 km/h (30 mph) or less

      
      Powertrain > Engine and ECT > Active Test

      Active Test Display
      Control the Shift Position

      Data List Display
      Shift Status

      Note

      
      

      • This test can be conducted when the vehicle is stopped.

      • When shifting gears using the Active Test function, do not operate the accelerator pedal for 2 seconds before and after shifting gears.

   8. Check the vehicle speed and the gear when the engine speed is 1000 rpm.

      Tech Tips

      Because the torque converter has not engaged, it may be difficult to obtain the speeds specified in 4th, 5th and 6th gear, however a difference of speed should still be evident following each gear change.

      Standard
      1st 2nd 3rd 4th 5th 6th 8 to 12 km/h (5 to 7.5 mph) 15 to 19 km/h (9.3 to 11.8 mph) 21 to 25 km/h (13.0 to 15.5 mph) 31 to 35 km/h (19.3 to 21.7 mph) 44 to 48 km/h (27.3 to 29.8 mph) 52 to 56 km/h (32.3 to 34.8 mph)

   9. Compare the ECM commanded gear and the actual gear.

      Result

      System Condition ECM Gear Shift Command Proceed to 1st 2nd 3rd 4th 5th 6th Malfunction Shift solenoid valve SL1 Stuck ON 1st 2nd 3rd 4th 4th 4th A Shift solenoid valve SL1 Stuck OFF N*1 N*1 N*1 N*1 5th 6th Shift solenoid valve SL2 Stuck ON 4th 4th 4th 4th 5th 6th B Shift solenoid valve SL2 Stuck OFF 1st 2nd 3rd 1st N*1 N*1 Shift solenoid valve SL3 Stuck ON 2nd 2nd 3rd 4th 5th 6th C Shift solenoid valve SL3 Stuck OFF 1st 1st 3rd 4th 5th N*1 Shift solenoid valve SL4 Stuck ON*3 3rd 3rd 3rd 4th 5th 5th D Shift solenoid valve SL4 Stuck OFF 1st 2nd 1st 4th N*1 6th Shift solenoid valve SLT Stuck ON N*2 N*2 N*2 N*2 N*2 N*2 E Shift solenoid valve SLT Stuck OFF*3 1st 2nd 3rd 4th 5th 6th

      Tech Tips

      
      

      • *1: Neutral

      • *2: If shift solenoid valve SLT is stuck on, the line pressure will be low. Therefore, the amount of torque that can be transmitted by each gear is less than the normal limit. When the engine power exceeds this lowered limit, the engine speed will increase freely.

      • *3: When shift solenoid valve SLT is stuck off, gear shifting is normal.

   
   

   B

   GO TO DTC P0776 Click here

   C

   GO TO DTC P0796 Click here

   D

   GO TO DTC P2808 Click here

   E

   GO TO DTC P2714 Click here

   A

3. INSPECT SHIFT SOLENOID VALVE SL1

   
   
   1. 

      *1	Shift Solenoid Valve SL1

      Remove shift solenoid valve SL1.

   2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition 1 - 2 20°C (68°F) 5.0 to 5.6 Ω

   3. Apply 12 V battery voltage to the shift solenoid valve and check that the valve moves and makes an operating noise.

      OK
      Measurement Condition Specified Condition Battery positive (+) with a 21 W bulb → Terminal 1 Battery negative (-) → Terminal 2 Valve moves and makes an operating noise

      Result
      Proceed to OK NG

   
   

   NG

   REPLACE SHIFT SOLENOID VALVE SL1 Click here

   OK

4. INSPECT TRANSMISSION VALVE BODY ASSEMBLY

   
   

   1. Check the transmission valve body assembly.

      Click here

      OK
      There are no foreign objects on any valve.

      Result
      Proceed to OK NG

   
   

   OK

   REPAIR OR REPLACE AUTOMATIC TRANSAXLE ASSEMBLY Click here

   NG

   REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY Click here