Has codes p0240,p0100,p0089 replaced all sensors
With the engine off and the battery negative cable disconnected, check all electrical connections at the o2 sensors, MAF and elsewhere. Under-hood temperatures tend to cause some oxidation on the terminals themselves. I've seen this issue with nearly every Volvo I've owned. Use electronics cleaner and dielectric grease on the connectors, especially on the MAF connector.P0240 (Catalyst working below efficiency threshold) means the downstream (2nd) o2 sensor is not moving. The reason for this sensor's existence is pretty simple - detect catalyst efficiency and possibly failure in the field. The upstream sensor must be in good condition and not 'lazy', meaning it is slow to respond to the oxygen levels coming out of the exhaust. It must be quick to respond. The downstream o2 sensor, however, usually doesn't change state as much, meaning the catalyst is doing its job. The idea is that if that downstream sensor starts to mimic the upstream o2 sensor activity, catalytic function can be inferred to be less than normal. Ensure the connections are good on both sensors. Replacing only the upstream o2 sensor will not cure this. Catalytic convertor failure is rare in the field but if you have been running rich, it's possible a large quantity of unburned fuels have destroyed or eroded the substrate. The only way to tell is put a scan tool on the car and monitor both sensors, capturing any freeze frame data along the way. Upstream sensor should be rapidly changing state and downstream should be changing state much more slowly.P0100 (MAF circuit - malfunction) usually points towards wiring issues or problems with the connector, especially if the MAF is known good.P0089 (Fuel pressure - regulator) could be a worn fuel pump, clogged filter or the regulator itself. Have the fuel system pressure tested, verifying components along the way.If all checks pass at this point, it is possible that the connections at the ECM itself need cleaning (do not unplug the ECM with the battery negative cable connected). If you perform this procedure do so with extreme caution and scrupulous cleanliness. Allow the cleaner to completely evaporate off the terminals or there could be a serious short condition that will destroy that 600 dollar computer.
