Seat Tarraco automatic transmission issue

The symptoms you describe strongly suggest an issue within the automatic transmission control system, specifically affecting the park engagement mechanism. The engine's inability to start, coupled with the check engine light and shifting anomalies, indicates a potential failure in the control unit's ability to correctly identify and engage the 'P' position. I recall encountering a similar problem on a 2017 Volvo XC60, albeit with a different transmission manufacturer, where a faulty solenoid within the valve body caused intermittent park engagement failures. The stored error codes are paramount in directing diagnosis; have you retrieved the specific codes? Knowing the precise fault codes will allow a more informed assessment of the situation. Furthermore, examine the gear linkage for any signs of physical damage or misalignment; though less probable, a mechanical impediment could manifest similar symptoms.

Thanks for the detailed response. I did retrieve the error codes; it's P173400, indicating a mechanical fault in the gear selector mechanism. You mentioned checking the gear linkage – could you elaborate on what specifically I should be looking for? Is there any way to test the shift lock solenoid?

P173400 corroborates a mechanical issue within the gear selector or linkage. Inspect the linkage for any looseness, corrosion, or physical obstructions that might impede its full range of motion. Focus particularly on the points where the linkage connects to the transmission and the gear selector lever within the cabin. Regarding the shift lock solenoid, diagnosing it in situ without specialized equipment is challenging. Resistance measurements using a multimeter can provide some indication of its electrical integrity, but a functional test requires actuation, typically through diagnostic software. Given the symptoms and error code, a comprehensive diagnostic procedure by a qualified technician is warranted. While it is possible to perform rudimentary checks, attempting extensive repairs without proper expertise can potentially exacerbate the problem. It is prudent to consult a workshop.

Took it to a trusted workshop as suggested. They confirmed the control unit fault in the automatic transmission. Replacement and coding set me back 1000€, but the Tarraco is shifting smoothly again. Thanks for the insight; it saved me a lot of unnecessary diagnostics.