90, 240 sedan

B230F, non-turbo

My 240 Check Engine light is coming on. This is the first time it has happened since I owned the car (10 months). The OBD says it is a 1-1-3 and a 2-3-2 code. The 2-3-2 is fuel system is compensating for rich or lean mixture at idle. The 1-1-3 is fault in injector(s).

I have done all the tests possible for the injectors, except for actually taking them out to see the spray pattern and volume. But since they passed all the other tests, and since I am told injectors rarely fail, I see no use in messing with the injectors any further. I believe something else is going on. The CAT on my car is bad and getting worse. I do not get the continuity it is supposed to receive from the O2 Sensor (Green Wire), when doing the ECU connector input test.

The O2 Sensor connector is getting the proper Voltage from the Main Relay (R/Y wire) Ground Continuity (Black wire), and OHMS from the Heated Wire Connector (two prongs on connector). Since I figured all this out I expected the 2-3-2 code about the fuel system compensating for rich or lean mixture. What I do not understand is why I am getting the 1-1-3 code (injectors).

Here are a few other things that happened that might give a clue. When I had gotten this car it had been neglected to a degree. The owners had it fixed by local non Volvo mechanics as it needed repairs, but were not aware of anything else they should be doing, like preventive maintenance. So I was fixing it up as I found things that needed attention. Being busy with work and other matter in life I could only devote my time to the most critical and necessary things first. So I had never even cleaned it. Recently, I decided to clean the engine. It was filthy. At least, it does look better. But I have to wonder, did I make things better or worse by doing that?

Well, first I took the precaution of taking the battery out of the car, and cleaning the Alternator by hand and then covering it with Saran Wrap type plastic. I used Simple Green on almost everything, except for some all metal parts that were extremely dirty, and I used GUNK on them. I avoided getting any GUNK on any non metal parts. I also avoided getting too much of the Simple Green on the electrical connectors. After I was finished I rinsed everything off with extremely hot water from a 2 gallon hand held pressure tank (which worked well). I let it all dry. While the engine was drying off, I used a plastic safe quick drying electrical contact cleaner and sprayed up all the connectors. I fired it up and everything was okay.

The next day I did the underneath of the front part of the car the same way. I may have hit the outside of the O2 sensor with either GUNK or Simple Green, I don't remember. I have since learned that the O2 Sensor has slotted vents on the outside to allow air into the sensor. I would assume and that you should not clog them up. I wonder if that's what I did with the cleaners. Next time I will either remove the O2 Sensor or cover it up. But a local mechanic friend of mine who is a decent mechanic says he doubts my cleaning the engine or hitting the O2 sensor with the any of the cleaners or the water did any harm. He also said the CAT has not destroyed the O2 Sensor, but more likely the O2 Sensor failing has destroyed the CAT. The CAT was on its way of going bad when I first got the car. I almost failed the NOX test (borderline). The only logical thing I can think of is that the O2 Sensor has been bad all along or failing more and more, and after it finally went bad it did the CAT in. About a month ago I started hearing this odd rattling sound, and I finally located it. The CAT. The sound was also hard to trace because of several other related sounds from the front muffler hitting nearby metal, and a loose preheater shield.

But my cleaning those electrical contacts might have just made the entire system work like it was supposed to be working all along, and so I am now just getting the codes I should have seen before. I noticed the input data to the ECU connector is in greater detail than the output analysis data from the ECU to the OBD socket.

I'm not that experienced and wanted to know if there was any way the inputs to the ECU from the failed O2 Sensor and the probably backed up exhaust from a probably partially clogged CAT, could cause the fuel system ECU to analyze those inputs as a problem from the injectors? Thanks, Bruce.