Volvo: Reset up arrow indicator for 94 Volvo 850, transmission control unit, transmission control module

Question
The up arrow indicator on the instrument panel is flashing, I would like to reset it to see if it will come back or if it is just a fluke.

Answer
Bill,
That would be an indication of a fault in the transmission control unit. Go to the diagnostic test box (front right side under the hood)test box A plug the pigtail into A-1 and begin reading and recording the codes. Ignition in on position.
Stored Diagnostic Trouble Codes (DTCs) can be read off and erased in DTM 1. A short press on the button on the DLC will start the DTC read-off procedure. If the control module replies by flashing code 1-1-1 no faults have been registered, so no DTCs have been stored. If the control module replies using any other flashing code sequence it is a DTC that has been stored. Use the table in the section D. Diagnostic Codes to identify the reason for the DTC being set.

The control module can store a maximum of five DTCs. The fault must be corrected and the DTC erased before further DTCs can be stored in the transmission control module.

Erasing DTCS



 



It is only possible to clear the data link connector (DLC) of codes after reading off all the codes at least once and the first code stored at least twice. The procedure for erasing stored DTCs is as follows:



Ignition ON
Press the button and hold down for more than five seconds. Release the button.
Wait for the LED to light.
Press the button again and hold down for more than five seconds. Release the button.
Make sure that the DTC's have been cleared by reading off the DTCs again.
Also you can disconnect the battery for 5 minutes and see if that will clear the codes. Now at this point you will not be able to read those codes.