I replaced the plugs and wires (routine maintenance, after 40,000 miles, plugs looked good - slightly worn electrodes, all with grayish color on ends) on my '92 SSE */c and also replaced the valve cover gaskets. It ran fine during the test drive afterwards. But the next day the SES light turned on and off a few times while I drove to work. The error codes were 13 and 44, both of which are for the o2 sensor. I thougt maybe I had bumped the wire while replacing the rear valve cover gasket, so I bent the sensor wire so it was completely vertical again, cleared the error codes and continued to drive the car. The SES light didn't come on at all the next day, so I thought it was ok. But this morning the light came on again and this time it stayed on for a few minutes and then turned off. Then while I was stopped at a light the engine idle jumped from 750 RPMs to 1,000 RPMs for a few seconds and then dropped back down to 750 again. This never happens when the engine is hot. Now there'* only code 44, which is for a lean o2 sensor reading.

I don't know how old the o2 sensor is, so I'm gong to replace it tonight anyway.

Is there another problem that could cause this error code also? Could this be caused by a growing crack in the exhaust manifold before the o2 sensor (see my other related post)?

I'm sure I moved the wire a little while working on the car, but that shouldn't have caused the sensor to fail. It seems odd that these 02 sensor error codes only began after I worked near that area on the car. Could it just be a strange coincidence?

Well, if anyone'* interested, here'* what I learned yesterday.
The '93 factory shop manual'* code 44 diagnostics showed a 3-wire o2 sensor and had no mention of replacing the sensor itself :?: . I know for a fact that my '92 and '93 both have a 1-wire sensor. So I looked in the '92 factory shop manual'* code 44 diagnostics, and it showed the correct 1-wire sensor and mentioned the replacement of the sensor.

I disconnected the o2 sensor and measured the voltage to the connector while the engine was running. It measured 390 mV, and this is within the expected range as per the diagnostics, so the ECM signal and ground reference were ok. Then I reconnected the o2 sensor and measured the voltage again, while the engine was running and the sensor was at normal temp (hot). The voltage fluctuated slightly between 220mV and 400mV or so. So the ECM was correct in reporting the lean error.

I went to replace the sensor and found that it wasn't threaded tightly into the exhaust manifold! Since I was going to replace it anyway, I did that and measured the voltage again. Now the voltage fluctuated quite a bit between 300 mV and 850 mV or so.

Problem solved.