Testing 850 trouble codes.
Here is a write-up on Volvo – 850 Trouble Codes. Like on any “Mode” change with the diagnostic box under the hood, press the button two times for mode two and 4 times for mode 4. I hope that this helps someone. Oh, and always, Victor Rocha who is a member here can rebuild your ABS module if that’s your problem (it is over 90% of the time with faulty ABS functioning).
If no faults were found while performing procedures in the F – BASIC TESTING article, proceed with self-diagnostics. If no fault codes are present, proceed to the H – TESTS W/O CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.).
NOTE: All voltage tests should be performed using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in testing procedures.