P1400 Differential Pressure Feedback EGR Circuit Low Input (Dealer TSB Number: 99103 addressed some possibles with this issue)
p0135 Heater O2 Sensor1 Bank 1 (This is the first sensor nearest the engine)
P0325 Knock Sensor
The last code often sets with almost any other problem, there is probably nothing wrong with the knock sensor itself, it's a passive part.
The O2 sensor may be bad, but it may also have a broken wire about six inches up the harness where there is a splice, this is a COMMON problem on these vehicles.
The P1400 I would not worry about until you get the O2 sensor problem fixed. These codes tend to daisy-chain on these vehicles, sometimes one problem will cause 3 codes, I've seen it many times.
Trouble code P0135 means:O2 sensor heater circuit malfunction (Bank 1 Sensor 1)
Trouble code P0135 means: HO2S Heater Performance Sensor 1
it is the ignition coil is the problem replace it p0135 for Volvo not sure about p1081
Trouble code P0135 means:O2 sensor heater circuit malfunction (Bank 1 Sensor 1)
Trouble code P0135 means:O2 sensor heater circuit malfunction (Bank 1 Sensor 1)
Trouble code P0135 means: O2 Heater Circuit (Bank 1, Sensor 1)
Trouble code P0135 means: O2 Heater Circuit (Bank 1, Sensor 1)
Trouble code P0135 means:O2 sensor heater circuit malfunction (Bank 1 Sensor 1)
Trouble code P0135 means:O2 sensor heater circuit malfunction (Bank 1 Sensor 1)
Trouble code P0135 means:O2 sensor heater circuit malfunction (Bank 1 Sensor 1)
Trouble code P0135 means:O2 sensor heater circuit malfunction (bank 1,sensor 1)
Trouble code P0135 means:O2 sensor heater circuit malfunction (Bank 1 Sensor 1)