89 240: fault 113 and 232
 

Need some pointers.Recently used BG products intake flush, to flush the air intake ,and after the flush, the check engine light came on. I checked o2 sensor per the Bentley manual. Voltage fluctuated from .01 to .09,( the spec. is .04 to .08). The heater resistance was .04 hot ( spec. calls for 13 ohms) So I replaced the o2 sensor @ $130. Also performed injector cutout test,( unplugged and reconnected each when idling ) and all injectors are working. Removed injectors and replaced o-rings and inspected tips.Tips look good,but did not check spray pattern. Old o2 sensor tip was gray indicating rich condition. The codes cleared,but check engine light came back on when started. What am I missing ? What else can cause an active code 113 ?
The car starts,and runs great,but due to rich condition,fuel mileage is decreased.

Fault 131,232
 

On a hunch,I disconnected the battery neg. cable for 30 seconds,then reconnected to battery. Turned on ignition,and started the car.Check engine light is now OFF! Over a year ago the check engine light came on for the knock sensor. Replaced the knock sensor, and problem remained. Unplugged ECM to ohm the knock sensor circuit, it checked out good. After plugging the ECM back in ,light went off,and problem disappeared . Several months later knock sensor fault reoccurred again.I unplugged the ECM and the fault cleared. I'm starting to think the ECM has a personality disorder ! Why do people like these old Volvos so much ? The parts are expensive and they require constant tinkering. ugggg....!!!