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How to Fix the P1734 Code on a Citroen C4 Picasso with BMP6 Gearbox

Model: Citroen C4 Picasso MK 2 - Years: 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022
Part: Warning light – error code

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Video tutorial

On the Citroen C4 Picasso with BMP6 automatic gearbox and 9HC engine shown in the video, the error code P1734 was detected, indicating a communication or consistency issue between the engine control unit and the gearbox control unit, which consequently remains stuck in neutral for safety reasons, preventing gear engagement.

The cause could be a fault in the gearbox control module (TCM) which may have suffered an internal failure or lost its programming.

If reprogramming is insufficient, replacement may be necessary. A faulty sensor inside the gearbox could also have sent an incorrect signal to the TCM, or a loose or corroded connector could be the cause; additionally, low gearbox oil level or degraded oil quality over time may also be valid causes.


Posted on 4 June 2026 by ScegliAuto


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by ScegliAuto

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