I forgot to tell you, when you drive the car you have to shift it manually when this error code has been set to avoid damaging the tranny. The car should be driven from a stop with the shift selector in "L" (Low) then pushed through the gear positions till you end up in "D" (Drive) for normal cruise.

And here's an explanation of "Test Position 4" referred to in the previous post:

Test Mode No. 4 (Activating Individual Components)
1) Test mode No. 4 activates individual components to verify
operation when a specific code is input into diagnostic unit.
Components are activated 6 times in sequence. Shift lever must be in
"P" or "N" position and vehicle must be stopped.

Rate of code transmission between TCM and diagnostic unit can be changed to 2 or 10 times the basic rate.
Doubled rate can be used for reading codes from diagnostic unit LED.
Highest rate is selected automatically when Volvo scan tool is used.

2) To activate test mode No. 4, push diagnostic unit button 4
times. Enter code for chosen component. See COMPONENT ACTIVATION CODES
table. One digit is entered each time diagnostic unit LED is lit.
Diagnostic unit LED flashes when chosen component is activated. After
testing components, system automatically exits test mode No. 4.

COMPONENT ACTIVATION CODES
................................................................
Component Code
No. 1 Shift Solenoid ................................. 342
No. 2 Shift Solenoid ................................. 343 <<<
Lock-Up Solenoid ..................................... 344
Line Pressure Solenoid ............................... 411
Warning Indicator Light .............................. 412
Drive Compensation (1) ............................... 414
Torque Limiting TC2 (1) .............................. 422
Torque Limiting TC1 (1) .............................. 423
Basic Code Transmission Rate ......................... 311
2 Times Basic Code Transmission Rate ................. 312
10 Times Basic Code Transmission Rate ................ 313

(1) - Engine idle speed will change during activation.
..............................................................

This will just test the individual components as you enter their code.

I'll let you know if I forgot anything else...... Mike