91 300E 2.6
This CEL code came up today. I'm at a lose as to where to start looking for a remedy. I disconnected the power to air pump years ago after replacing it and then having it fail in the first year. I've searched but not seen any real direction to start looking. Any direction will be appreciated.

The air injection system consists of the air pump, diverter valve, vacuum switch-over valve, and the O2 sensor.

While driving the engine ECU will switch on the air pump & then monitors the O2 sensor for very lot voltage readings.

Check the vacuum lines & does the air pump come on when the engine is cold?

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I'll start checking the vacuum lines. The pump itself has been disconnected for years now because it was so noisy.