C4 Grand Picasso gearbox faulty message FIXED

[Mejmag]

Hi guys, I had the “gearbox faulty” message and it cost me just £44 to fix!!! Here’s how:

I have a 2009 c4 Grand Picasso diesel, with the semi auto gearbox, gear lever on the steering column. I had an intermittent problem, a beep followed by a message saying “gearbox faulty”. When the message appeared, I would shift the gear lever into “A” and sometimes it wasn’t recognised, the screen would still show I was in N, and the car wouldn’t move. Other times the gearbox faulty message would appear and I would be able to shift into “A” then drive off without any problems. The same fault occurred when I shifted into reverse. The fault was very temperamental, but was gradually getting worse.

I reluctantly took it to my local approved Citroen dealer. They plugged it into the computer and said they think it’s the gear lever but they’re not sure. Cost to supply and fit was £520!! I politely declined. Fault codes they printed out for me were:

P1394 Gearbox ECU fault
P1718 Gear lever signal fault.

I found an excellent video on YouTube which explains how to remove and repair the gear lever selector:

I couldn’t see anything wrong with my gear lever selector’s soldered joints, but I decided to buy a second hand one on eBay for £44. Fixed!! The gearbox faulty message has not returned, and I can select gears as normal.

Removing the gear selector is very easy and takes 10 minutes. When you buy a second hand gear lever, be sure that the number on the back of it is identical to the number on the back of your faulty lever.

Good luck guys!!

[Maxman71]

Been having the same issue for 3 weeks now,not been able to some times change from N to R or A1/M but more so in the last week.
Was told at garage I normally go to that it would be the actuator and is booked in next month to be looked at.
I'd had enough today and decided to research on it and found this thread,thankyou to however posted the yt link ,after watching it
I thought sod it,its worth a go.
30 minutes later from start to finish, striped down soldering done reassembled and tested all fixed for £0 and a little of my time ,this has saved me a shed load of money time and stress that I didn't need ,thanks again .

[yason]

30 minutes later from start to finish, striped down soldering done reassembled and tested all fixed for £0 and a little of my time ,this has saved me a shed load of money time and stress that I didn't need ,thanks again .

What did you resolder?

I'm having the same issue, I took the gear lever module into bits and the circuit board seems to be in very nice condition merely by eyeballing. I checked that all optical switches get a steady 5V reference and they output between 0.2-4.8V depending on how translucent the obstruction is when switched with a piece of paper. The led counterparts all get the same 1V + then some. I measured all the resistors and the two capacitors against their nominal values printed on them; they all seem to check all right. I had a hard time figuring out what the outputs are from the gear level module, is it just signals or if it speaks bus so I can't tell much about that. Citroen's wiring diagrams are often incomprehensible.

It's likely the gear lever module is at fault but not being an electronics expert beyond very basic knowledge I couldn't find an obvious fault with the circuit board. Looking to find a cheap used one to validate the location of the fault but I would like to ultimately root-cause it.