Automatic transmission
I have a 2000 Saab 9-5 Aero auto with engine code 2.3T. I rebuilt the AW50-42 transmission two years ago with professional help, fitting a new torque converter, and recently replaced the valve body and electrical harness. The transmission performs perfectly. However, between 50-60mph when not accelerating, the transmission and engine lights pop up consistently, especially with a very small amount of steady throttle to maintain speed. My Tech2 reader is showing the fault code ‘P0741 - Torque lock up circuit short or poor performance’. If I just slowly accelerate through 50-60mph to, say, 70-80 and drive at the higher speed, then decelerate to below 50, the code does not appear. If I drive all day below 50, the lights don’t appear. The code can always be cleared.
I have the ATSG manual for the AW50-42LE transmission, and my Tech2 can read and record live data, but I find this is time consuming as I am not totally skilled with it.
Derek Houghton
Given the work that has been carried out, I am making the assumption that the auto transmission fluid is in good condition and at the correct level.
Code ‘P0741’ refers to the torque lock-up solenoid and will normally be flagged if the output speed of the torque converter varies from the expected ratio of 100rpm for 10 seconds when it should be locked. The problem is normally down to one of three reasons: either the lock-up solenoid is faulty, the torque convertor clutch has failed or there is a wiring fault.
Given that the torque convertor and valve body has been replaced, if this included the torque converter clutch solenoid, I would say that the last option of a wiring problem is the most likely. As you have fitted a new loom, I would concentrate on the connections. The most common wiring problem to produce the code ‘P0741’ is if the circuit shorts to earth. With this in mind, I would also check for anywhere the loom may have rubbed through. You should also inspect the connections to the gearbox speed sensor – a poor connection in this area can trick the ECU into believing there is a variation in speed.