Torque converter lock-up clutch (WSK) actuation operational check using actual values

The output signal (output stage) of the lockup clutch at the TCC control module (pin 2) can be checked. The function of the lockup clutch can be checked together with actual value 03.

In addition the shift points for the lockup clutch can be checked. The sub-menu nT/nP shows a ratio between the output rotor speed and input rotor speed calculated by the HHT for each actuation (actual value 01 ON). When the vehicle is stationary (in neutral position) or the vehicle is unladen a value which is too high is displayed in the lower gears as the output rotor is not braked sufficiently. The value must be between 0.7 and 0.8 for a correct recording.

If the value is 1.0 the engine speed sensor is defective or installed incorrectly (distance to ring gear on converter is too great), see actual value 02.

In the event of a complaint (e.g. no fault code appears if there is a defective pilot control valve, engine speed sensor and turbine speed sensor), this value can be checked on a road test with a drive train under load and compared with the table in the Repair Instructions, Chapter 8, page 5. When the vehicle is unladen it must be shifted into the highest gear and accelerated slowly.

If the lockup clutch engages too early when the splitter switch is switched upwards, check the function of the "transmission splitter switch" (actual value 04).

If the oil level is too low, the lockup clutch does not engage or engages too late.

If ON is displayed, but the lockup clutch does not engage (TCC display lamp goes out):

– Check relay K1-35 and cable to relay K1-A35 for open-circuit.

– Pilot control valve (in TCC control box).

– Lockup clutch shift valve stiff/defective (in TCC control box).

– Lockup clutch pressure valve stiff/defective (in TCC control box).

If ON is displayed, but the lockup clutch does not engage (TCC display lamp stays on):

– Check relay K1-A35, K2-A35 and wiring.

– Wiring from relay K1-A35 to control module or control module defective.

If ON is displayed and the lockup clutch is permanently engaged (TCC display lamp does not come on):

– TCC control module defective or short-circuit to UB+ at supply lead to or at relay A35-K1.

If the lockup clutch does not disengage when the kick-down switch is operated (actual value 03 is in order):

1. Check kick-down switch, voltage supply and wiring (actual value 07 with EMR, actual value 13 with FMR).

2. Replace control module on an experimental basis.

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