Time to chime in.

I recently had a 1-1-3 happen to me, but the "fault in fuel injectors" in the Haynes manual may not be correct.

Check here: https://www.volvoclub.org.uk/faq/EngineOBDCodes.html
Here it says 1-1-3 means "Fuel trim (lambda control) too lean or rich".

I agree with Art that this may not be related to the O2 sensor as in my 245 the cause turned out to be an intermittent fault in the fuel pressure regulator.

Lately, it started misfiring just after the cold start and then clear up within 30 s or so. Touching the accelerator during this half a minute only made it worse. So it was start, wait a minute, drive.

After some thinking about the functioning of the LH 2.4 during the first few minutes, when the O2 sensor doesn't give reliable data and is thus ignored by the ECU, I decided that the pressure regulator was the most likely cause.
No, there was no fuel leakage on the vacuum side and yes, there was also a healthy volume of fuel going back into the return line. But the replacement solved the problem.

So, the 1-1-3 during driving was probably thrown when the regulator decided to stick for a moment resulting in hitting the limits of the adjustment range.
After the replacement of the regulator, no codes have been thrown and the too rich running just after the cold start has been solved.

In other words: 1-1-3 doesn't really tell you the cause, only a symptom. You will have to exclude possible causes one by one.