The VW Jetta with the 2.5 engine has a pressure sensor in the secondary air hose. It is common for this sensor to go bad and I have seen outside shops replace this sensor with a map sensor and the came will come back in a few days with the same problem.
The map sensor and secondary air pressure sensor look the same and have the same connector but they do not work the same.
The part number for the secondary air pressure sensor is 07C-906-051 and the map sensor part number is 03C 906 051 the map sensor is located down by the throttle body and the sec air pressure is located in the hose next to the battery.
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