Torque Converter Clutch, No RPM Drop at Lockup

Name of Code:
Torq Conv Clutch No RPM Drop at Lock-up

When Monitored:
When all of the following steps are taken:
1. None of the following matured or maturing trouble code conditions:
a. TCC solenoid circuit
b. Any cam/crank-related code
c. Vehicle speed signal
d. Any TPS-related code

2. Battery voltage greater than 11.0 volts
3. Vehicle speed greater than 60 mph during step 5.
4. Run vehicle in third gear at about 40 mph with torque converter unlocked for at least 10 seconds.
5. Apply 1/3 throttle while making sure transmission does not downshift. Back off on the throttle slightly until the torque converter locks. Keep the torque converter locked for at least 5 seconds by holding the throttle and vehicle speed constant.

Set Condition:
Torque converter malfunctions that are detected are the torque converter not locking up properly when desired, and the torque converter not unlocking properly when desired. A minimum amount of improvement in torque converter efficiency is expected after the torque converter is locked. This expected minimum improvement will not be seen when the torque converter is malfunctioning. Three consecutive test failures over one trip will store the trouble code.

Theory of Operation:
The torque converter lock-up system locks the crankshaft to the output shaft of the transmission when vehicle road load is stable and transmission is in third gear. This action reduces transmission oil heating, and improves fuel economy. The lock-up system is controlled by the powertrain control module.

Possible Causes:
- Drive wheel size is bigger than standard wheel size or smaller than spare wheel size
- Low transmission oil level or pressure
- Debris in transmission oil
- Incorrect speedo gear for the front wheels
- PTU solenoid not securely connected or stuck
- Malfunctioning lock-up valve in transmission
- Hydraulic leak at torque converter lock-up clutch
- Worn out friction material on friction disc in torque converter
- Failed gear box or differential
- Powertrain control module failure
- Worn out connector terminals/wires