1991 240 Diagnostic code 1-3-3

[faof2]

1991 Volvo 240 wagon 132,000 miles California car. Engine performs erratically at idle and at speed. Right now I am checking for possible causes. Today I am specifically asking about diagnostic code 1-3-3 (Throttle switch idle contacts misadjusted or shorted to ground) in socket 2 which has appeared three times in the previous two months. I would like to hear from anyone who had this code and corrected the situation. What condition did you find, and what did you do to correct it?

Curiosity question: In the Bentley manual page 241-6, the table c fault code column 3 entitled "Check Engine" light on indicates "No" for code 1-3-3. Is this another Bentley error, or is this telling me something I need to know. In other words, why does this code cause the CEL on my car when the chart indicates this code does not trigger the CEL?