BMW Transmission Fault Code – P0741 – Torque Converter Clutch
This answer is applicable for many BMWs in addition to the one listed below.
car year: 2002
car model: 530i
I changed the auto trans fluid and filter at 82000 miles.,now 90000 miles and fault code p0741 is showing . I cleared it a few times and it keeps coming back again after a few weeks. I checked the fluid and it was o k. Which parts need changing?
The P0741 fault code is a transmission fault code for “Torque Converter Clutch Performance or Stuck Open”. This is telling us that there is a problem with the torque converter’s lock-up clutch.
Most BMW models with automatic transmissions, from the late ’80s-on, utilize a clutch within the torque converter. The clutch engages when at a steady cruise at highway speeds. This bypasses the normal fluid coupling through the torque converter and improves fuel mileage.
The P0741 fault code could be due to a problem within the lock-up clutch itself or the hydraulic control circuit within the transmission control valve body or the electrical control circuit or solenoid that operates the hydraulic circuit via the valve in the valve body. Additionally, the fault could be as simple as a corroded (or fluid soaked) harness connector plug at the transmission (where the vehicle electrical harness connects to the transmission).
Your transmission is a 5-speed model (A5S-325Z). This means that you will have four up-shifts to be in 5th gear. Once in 5th gear (note that this all applies to earlier 4-speed auto transmissions, but the top gear will be 4th, not 5th), and you are at a steady speed, the transmission should tell the clutch in the torque converter to lock-up, or engage. This is like another final gear change …. as if you had another gear, or a 6th gear. Before the converter locks, you can slightly vary the accelerator and you can see the engine RPM vary slightly, without the vehicle speed changing. Once the converter locks up, if you slightly vary the throttle, the RPM will not change as it does with the converter unlocked. It will act like a manual transmission. If you press the throttle a bit more, the converter will unlock and you will see the RPM jump up a couple to a few hundred RPM.
So, here’s what you should experience, if you run through a test to see if the converter is locking:
1) Shifter in D – Drive
2) Starting to move, you will be in 1st gear
3) Note shift to 2nd gear as you accelerate (as each gear is changed, RPM will drop by a few hundred RPM).
4) Note shift to 3rd gear
5) Note shift to 4th gear
6) Note shift to 5th gear
7) Lighten up on the acceleration to transition to a steady cruise. Watch the RPM. Play with varying the rpm by a couple hundred RPM and note that the RPM changes but the vehicle speed stays fairly constant.
8) Back to steady state running (above 45mph) and note when (if ) the converter locks up and the RPM drops by another 200 to 300 RPM. At this stage, if you slightly vary the throttle (as in step 7) the RPM will not change.
9) Push on the throttle a bit more and the converter will unlock and put you back to step 7. If you push harder on the throttle, the transmission will downshift to 4th gear (step 5). If you lighten up, it will shift back to 5th … and then into lock-up.
If you can not detect the lock-up, then the clutch is not functioning. We would suggest that you first inspect the transmission harness electrical connection plugs for fluid or corrosion. After this, a more detailed code reading will be required, using a full diagnostic tool that would be employed by a BMW independent or dealer technician.