rudolf_herrmann1
Citan Gear Shift Issue
Summary of the thread
A 2017 Mercedes Citan diesel with 106,993 km is experiencing gear shift issues, including a dead gear shift indicator, inability to engage gears, and erratic transmission behavior. The problem is suspected to be a defective control unit, as indicated by error code P0702, which points to a transmission control system electrical issue. Suggested solutions include inspecting the wiring harness for loose connections and potentially replacing the control unit, with a recommendation to seek professional diagnostic and repair services. The issue was resolved by replacing the control unit at a workshop, restoring smooth gear shifting.
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4 comment(s)
rudolf_herrmann1 (community.author)
Good shout. I did give the wiring a quick look-over, but didn't go too deep. The exact error code is P0702 Transmission Control System Electrical. Is that the same code you experienced? Also, where exactly is the transmission control unit located in the Citan? I want to give those wires a proper inspection before I throw parts at it.
davidtiger3
P0702 rings a bell. It's been a while, but I think that was it. The control unit is usually tucked away somewhere near the gearbox itself, possibly under the vehicle. Honestly, given those symptoms and the error code, and if wiggling the wires doesn't do anything, you're probably looking at a new or refurbished control unit. My advice would be to take it to a reputable workshop. They have the diagnostic tools to confirm the problem and properly program the new unit. You're not going to be able to do that yourself.
rudolf_herrmann1 (community.author)
I appreciate the insight. I think you're right, time to bite the bullet and take it to the shop. Sounds like I'm in over my head with this one. Turns out it was indeed the control unit. The workshop confirmed it and swapped it out. It cost me just shy of 1000€ as expected, but at least it's shifting smoothly again. Thanks for the help!
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MERCEDES
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CITAN
davidtiger3
Sounds familiar. I had similar issues with my Citan, though the mileage was different when it happened to me. The shift knob felt loose, and the digital display was all over the place. I remember the error codes pointing towards a sensor problem related to the gearbox. I'd be interested to know what specific error code you are seeing. Also, have you checked the wiring harness going to the transmission control unit? Sometimes a loose connection can cause similar symptoms. Have you tried any troubleshooting steps?