ELECTRONIC CONTROLLED AUTOMATIC TRANSMISSION SYSTEM, Diagnostic DTC:P2757

SYSTEM DESCRIPTION

The ECM uses the signals from the throttle position sensor, air-flow meter, turbine (input) speed sensor, output speed sensor and crankshaft position sensor to monitor the engagement condition of the lock-up clutch.

Then the ECM compares the engagement condition of the lock-up clutch with the lock-up schedule in the ECM memory to detect mechanical problems of the shift solenoid valve SLU, valve body and torque converter clutch.

MONITOR DESCRIPTION

Torque converter lock-up is controlled by the ECM based on the turbine (input) speed sensor NT, output speed sensor SP2, engine rpm, engine load, engine temperature, vehicle speed, transmission temperature, and gear selection. The ECM determines the lock-up status of the torque converter by comparing the engine rpm (NE) to the input turbine rpm (NT). The ECM calculates the actual transmission gear by comparing input turbine rpm (NT) to output shaft rpm (SP2). When conditions are appropriate, the ECM requests lock-up by applying control voltage to the shift solenoid SLU. When the SLU is turned ON, it applies pressure to the lock-up relay valve and locks the torque converter clutch.

If the ECM detects no lock-up after lock-up has been requested or if it detects lock-up when it is not requested, the ECM interprets this as a fault in the shift solenoid valve SLU or lock-up system performance.

The ECM will illuminate the MIL and store the DTC.

Example:

When one of the following conditions is met, the system determines that there is a malfunction.

• There is a difference in rotation between the input side (engine speed) and output side (input turbine speed) of the torque converter when the ECM commands lock-up.

  Engine speed is at least 70 rpm greater than input turbine speed.

• There is no difference in rotation between the input side (engine speed) and output side (input turbine speed) of the torque converter when the ECM commands lock-up OFF.

  The difference between engine speed and input turbine speed is less than 35 rpm.

INSPECTION PROCEDURE

1. Warm up the engine.

2. Turn the ignition switch OFF.

3. Connect the intelligent tester to the DLC3.

4. Turn the ignition switch ON and push the tester main switch ON.

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

6. Follow the instructions on the tester and read the Active Test.

   Item	Test Details	Diagnostic Note
   Control the Lock Up	[Test Details] Control the shift solenoid SLU to set automatic transmission to lock-up condition [Vehicle Condition] Throttle valve opening angle: Less than 35% Vehicle speed: 60 km/h (37 mph) or more	Possible to check the shift solenoid valve SLU operation

   Tech Tips

   This test can be conducted in the 5th gear.

7. Lightly depress the accelerator pedal and check that the engine speed does not change abruptly.

   Tech Tips

   
   

   • When changing the accelerator pedal opening angle while driving, if the engine speed does not change, lock-up is ON.

   • Slowly release the accelerator pedal in order to decelerate. Suddenly releasing the pedal will close the throttle valve and lock-up may be turned off automatically.

     

PROCEDURE

1. CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P2757)

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the ignition switch ON and push the intelligent tester main switch ON.

   3. Enter the following menus: Powertrain / Engine and ECT / DTC / Current or Pending.

   4. Read the DTCs using the intelligent tester.

      Result
      Display (DTC output) Proceed to Only P2757 is output A P2757 and other DTCs B

      Tech Tips

      If any other codes besides P2757 are output, perform troubleshooting for those DTCs first.

   
   

   B

   GO TO DTC CHART

   A

2. INSPECT SHIFT SOLENOID VALVE SLU

   
   

   1. 

      Remove the shift solenoid valve SLU.

   2. Measure the resistance of the solenoid valve.

      Standard resistance
      5.0 to 5.6 Ωat 20°C (68°F)

   3. Connect the positive (+) lead with a 21 W bulb to terminal 2 and the negative (-) lead to terminal 1 of the solenoid valve connector, then check the movement of the valve.

   4. Check the operating noise of terminal 1 of the solenoid valve.

      OK
      Solenoid makes operating noise.

   
   

   NG

   REPLACE SHIFT SOLENOID VALVE SLU

   OK

3. INSPECT TRANSMISSION VALVE BODY ASSEMBLY

   
   

   1. Check the transmission valve body assembly.

      OK
      There are no foreign objects on each valve.

   
   

   NG

   REPLACE TRANSMISSION VALVE BODY ASSEMBLY

   OK

4. INSPECT TORQUE CONVERTER CLUTCH ASSEMBLY

   
   

   1. Check the torque converter clutch assembly Click here.

      OK
      The torque converter clutch operates normally.

   
   

   NG

   REPLACE TORQUE CONVERTER CLUTCH ASSEMBLY

   OK

   REPAIR OR REPLACE AUTOMATIC TRANSMISSION ASSEMBLY