AUTOMATIC TRANSMISSION SYSTEM, Diagnostic DTC:P2757

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 shift solenoid valve SLU, the valve body and torque converter clutch.

MONITOR DESCRIPTION

Torque converter lock-up is controlled by the ECM based on the turbine (input) speed sensor NCO, output speed sensor SP2, engine speed, 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 speed (NE) to the input turbine speed (NCO). The ECM calculates the actual transmission gear by comparing the input turbine speed (NCO) to the output shaft speed (SP2). When conditions are appropriate, the ECM requests lock-up by applying control voltage to shift solenoid valve SLU. When shift solenoid valve 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 shift solenoid valve SLU or the 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 speed between the input side (engine speed) and output side (input turbine speed) of the torque converter when the ECM commands lock-up ON.

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

• There is no difference in speed 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. ACTIVE TEST

   Tech Tips

   Using the intelligent tester to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.

   
   

   1. Warm up the engine.

   2. Turn the ignition switch off.

   3. Connect the intelligent tester to the DLC3.

   4. Turn the ignition switch to ON.

   5. Turn the intelligent tester on.

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

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

      Engine and ECT

      Tester Display	Test Part	Control Range	Diagnostic Note
      Activate the Lock Up	Control shift solenoid valve SLU to set automatic transmission to lock-up	ON or OFF	Possible to check shift solenoid valve SLU operation. [Vehicle Condition] Throttle valve opening angle: Less than 35% Vehicle speed: 80 km/h (50 mph) or more

      Tech Tips

      This test can be conducted when the vehicle speed is 80 km/h (50 mph) or more.

   8. 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 rapidly, lock-up is on.

      • Slowly release the accelerator pedal in order to decelerate, but do not fully release the pedal. (Fully releasing the pedal will close the throttle valve and lock-up may be turned off automatically.)

PROCEDURE

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

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the ignition switch to ON.

   3. Turn the intelligent tester on.

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

   5. Read the DTCs using the intelligent tester.

      Result

      Result	Proceed to
      Only P2757 is output	A
      P2757 and other DTCs are output	B

      Tech Tips

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

   
   

   B

   GO TO DTC CHART Click here

   A

2. INSPECT SHIFT SOLENOID VALVE SLU

   
   
   1. 

      Text in Illustration

      *a	Component without harness connected (Shift Solenoid Valve SLU)

      Remove shift solenoid valve SLU.

   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) 5.1 to 5.5 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 2 Battery negative (-) → Terminal 1 Valve moves and makes an operating noise

   
   

   NG

   REPLACE SHIFT SOLENOID VALVE SLU Click here

   OK

3. INSPECT TRANSMISSION VALVE BODY ASSEMBLY

   
   

   1. Check the transmission valve body assembly Click here.

      OK
      There are no foreign objects on each valve.

   
   

   NG

   REPLACE TRANSMISSION VALVE BODY ASSEMBLY Click here

   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 Click here

   OK

   REPAIR OR REPLACE AUTOMATIC TRANSMISSION ASSEMBLY Click here