Monitor Description

Torque converter lock up is controlled by the ECM based on speed sensor (NT), speed sensor (NC), 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 counter gear RPM (NC). When conditions are appropriate, the ECM requests "lock up" by applying control voltage to shift solenoid DSL. When the DSL is turned on, solenoid DSL 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 DSL or lock up system performance. The ECM will turn on the MIL and store the DTC.

Example: When any of the following is met, the system judges it as a malfunction.

1. There is a difference in rotation between before and after torque converters even when the ECM commands lock up.

   (Engine speed is at least 75 RPM greater than input turbine speed.)

2. There is no difference in rotation between before and after torque converters even when the ECM commands lock up off.

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