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oskarshadow53

Fiat Fiorino Transmission Control Unit Fault

I'm having trouble with the transmission control unit on my 2007 Fiat Fiorino diesel with 135478 kilometers. The paddle shifters won't change gears, there's slippage and grinding during gear changes, the paddle shifters are sluggish, and the gearbox occasionally enters emergency mode. Diagnostic scrutiny reveals error registered within the error memory, strongly suggesting a defect within the control unit. Any ideas?

Summary of the thread

The 2007 Fiat Fiorino is experiencing issues with the transmission control unit, leading to problems such as gear slippage, grinding, and emergency mode activation. The error code P1729 indicates a fault within the transmission control module. Possible causes include electrical issues or a defective control unit. The recommended solution is to have the vehicle assessed by a qualified technician to confirm the diagnosis and replace the faulty transmission control unit, which resolved the issue in this case.

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4 comment(s)

thomasfox1

Sounds rough! Had similar craziness with my old Saab 9-3 Aero – also an auto 'box. It would randomly shift down gears on the highway, or refuse to shift up at all. Is the 'error memory' throwing up a specific code, or just a generic 'transmission fault' type thing? In my case, it was definitely electrical, playing havoc with the transmission. I am thinking the same for you: control unit problems.

oskarshadow53 (community.author)

The error message recorded is P1729, indicating a fault within the transmission control module itself. Given your experience with the Saab, could you perhaps elaborate on the nature of the electrical gremlins you encountered? Were there any specific diagnostic procedures or observations that proved particularly insightful in pinpointing the root cause?

thomasfox1

Right, P1729 points straight at the TCU. For my Saab, we checked all the wiring and connections first – apparently rodent damage is common. But eventually, it turned out to be the TCU itself. After that, nothing helped anymore. I'd strongly advise getting it checked by a workshop with the proper diagnostic tools. They can check the signals going to and from the TCU and confirm if it's truly toast. Sorry, but that’s what I would do.

oskarshadow53 (community.author)

I appreciate your insightful guidance. Following your recommendation, I had the vehicle assessed by a qualified technician. The diagnosis corroborated your suspicions: the transmission control unit was indeed defective. The repair, inclusive of parts and labor, amounted to approximately 1000€ and solved my problem. Thank you again for your invaluable assistance.

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FIAT

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FIORINO