A decurler is configured for use in an aqueous inkjet printer to monitor ink contamination of the indent roller in the decurler and generate a signal that maintenance is required prior to the printer beginning to produce wrinkled media sheets by the ink contamination on the indent roller. A reflective sensor is mounted on a shaft for bidirectional movement to sweep the length of the indent roller and generate electrical signals indicative of the presence or absence of contamination on the indent roller. The controller receiving signals from the reflective sensor compares the signals from the reflective sensor to a predetermined threshold prior to commencing monitoring of the indent roller to determine positions where the sensor is opposite the indent roller and positons where the sensor is opposite a frame in the printer.