Monitor Description

WARNING: This page is about a different car, the 2015 Lexus IS 250 and 2014 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.

Torque converter assembly lock-up is controlled by the ECM based on the transmission revolution sensor (NT), transmission revolution 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 assembly by comparing the engine revolution (NE) to the input turbine revolution (NT). The ECM calculates the actual transmission gear by comparing input turbine revolution (NT) to output shaft revolution (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 assembly.

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 malfunction of in the shift solenoid valve SLU or lock-up system performance.

The ECM will illuminate the MIL and store this DTC.

Example:

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

There is a difference in rotation between the input side (engine speed) and output side (input turbine speed) of the torque converter assembly 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 assembly when the ECM commands lock-up off.
(The difference between engine speed and input turbine speed is less than 20 rpm.)