A bad coolant sensor COULD mimic the issues a bad AMM could cause, mostly because a bad AMM can cause a variety of running conditions.

If your coolant temp. sensor is bad then the engine thinks it is cold when it is not. Therefore it will add fuel and run rich. The Oxygen Sensor SHOULD (in theory) notice the extra fuel in the exhaust and correct the A/F mixture however that has not been my observation. I've had a rich running condition where the O2 sensor was operating correctly (I checked the output voltage) but still did not correctly adjust the air/fuel mixture.

The good news is that it's very easy to test your coolant temp. sensor. Pull it out, dunk it into water of a known temperature, measure the resistance across the terminals and match it up to the chart in the Bentley Manual.

Here it is for the B230F LH2.2: http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/06/41/99/small/0900c15280064199.jpg

"Connect the ohmmeter between ground and terminal 2. Resistance depends on coolant temperature (see chart). As a reference, if the coolant is at 68°F (20°C), look for readings of 2300-2700 ohms. If the coolant is at 176°F (80°C), expect readings of 300-360 ohms. Hint: if the ohm reading is incorrect, perform the test again at the pins of the sensor. If the readings are now correct, you have a wiring problem, not a sensor problem."