Toyota Celica 2005 Repair Manual page 1006

DTC P0741
SYSTEM DESCRIPTION
The ECM uses the signals from the throttle position sensor, air−flow meter 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 trouble of the shift solenoid valve SL, valve body and torque converter
clutch or automatic transaxle (clutch, brake or gear etc.).
DTC No.
S Lock−up does not occur when driving in the lock−up range
(normal driving at 80 km/h [50 mph]), or lock−up remains ON
in the lock−up OFF range.
P0741
(2−trip detection logic)
S When lock−up is ON, clutch or brake slips or gear is broken.
(2−trip detection logic)
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 SL. When the SL is turned on, solenoid SL 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 re-
quested, the ECM interprets this as a fault in the torque converter clutch 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.
(a) There is a difference in rotation between before and after torque converters even when the ECM com-
mands lock−up.
(Engine speed is at least 100 rpm greater than input speed.)
(b) There is no difference in rotation between before and after torque converters even when the ECM com-
mands lock−up off.
(The difference between engine speed and input speed is less than 35 rpm.)
2005 CELICA (RM1131U)
DIAGNOSTICS
Torque Converter Clutch Solenoid Perfor-
mance (Shift Solenoid Valve SL)
DTC Detecting Condition
− AUTOMATIC TRANSAXLE (U341E)
S Shift solenoid valve SL is stuck open or closed
S Valve body blocked up or stuck
S Lock−up clutch
S Automatic transaxle (clutch, brake or gear etc.)
1005
Trouble Area
DI−805
DIAJC−03