2002 Jetta 1.8T Automatic: P1780 and P1850 Fault Codes - Battery Drain and Transmission Jerk Explained
I'm experiencing two diagnostic trouble codes on my 2002 Jetta 1.8T automatic: P1780 (Engine Intervention Readable) and P1850. Recently, I noticed a significant battery drain—my car loses power even when the engine is off, and multiple electrical components fail to turn on. When attempting to start the vehicle, the battery warning light does not illuminate, despite other dashboard lights functioning normally. This suggests that the car may not be detecting a functional battery for ignition purposes, which is unusual since it was working fine a few days ago. Additionally, when shifting from gear 1 to 2 or 2 to 3, I feel a sharp, sudden jolt—like a sledgehammer striking the transmission—which causes noticeable jerking. This first occurred during a drive and startled me significantly. Given these symptoms, I'm concerned about potential electrical faults or transmission issues. I'm now considering whether a dealership repair might be necessary, but I'd like to understand what these codes mean before making any costly decisions.
Thanks for sharing the details—this is a common issue with 2002 Jetta 1.8T models involving P1780 and P1850 codes, often linked to faulty battery connections or transmission control module problems. The sudden gear shift jolt may indicate a malfunctioning torque converter or sensor. I recommend checking the battery terminals and inspecting the vehicle's body ground connection before visiting a mechanic.