P1734 Gearbox actuator position in the gear selection shaft signal fault

[Georgie712]

Hi
First time posting, couldn't find what I was looking for so started a new topic, I hope that's okay. If not please let me know the right place to post.
My c4 grand picasso semi auto.
Is stuck in Neutral and showing Gearbox Faulty in dash, car wont always start and when it does there is a pause and 3 knocks and when engine running but idle car feels very juddery
Diagbox shows P1734 Gearbox actuator position in the gear selection shaft signal fault-Short to Earth, permanent fault. I'm waiting for a new jack to arrive to check the acctuator fluid tank, but quick look through the engine bay, I think it may be empty. What could cause this? And could that bring up this fault or does it indicate something else is going on, if so any ideas what it could be? Please help

[GiveMeABreak]

Be very careful as the actuator is pressurised, so the oil must only be filled once the system is depressurised. Then fill to the correct level and repressurise the system. You will need Diagbox or a professional level diagnostic tool to do this.

As for the fault code:

Fault Code:	P1734
Description of Fault:	Fault with the signal of the position of the gearbox actuator in the gear selection shaft : Short circuit to earth. The voltage of the signal is lower than 0,5 V The time of appearance of the fault code is 1s. The following conditions have to be met for the fault: - Ignition on - The starter motor is not operating Technical precision on the context of appearance of the fault code: Supply voltage correct Absence of fault codes P1586 - P1587
Conditions for Fault to clear:	No faults for 2 seconds
Downgrade Modes whilst Fault is active:	Engine running or in Stop and Start phase - The gear change is down-graded (Gear change takes longer) - The gears above 3rd gear cannot be engaged - Activation of Manual mode - Request for neutral accepted when vehicle stopped - If there is a request for reversal of the vehicle’s direction of movement, neutral is engaged - Gear changes prohibited if a malfunction appears while neutral is engaged - If there is a malfunction during a gear change : Emergency selection of neutral - If the vehicle has the Stop and Start system : Stop and start function deactivated Engine stopped - Neutral engaged if there is a request for reverse gear - Neutral engaged if there is a request for a forward gear while reverse gear is engaged - Gear changes prohibited if a malfunction appears while neutral is engaged - The engine can be started
Symptoms:	Warning lamp active (depending on equipment): MIL "SERVICE" warning lamp Sport warning lamp Snow warning lamp Automatic or 6-speed piloted manual gearbox warning lamps (Orange PRND triangle) Display of a "-" on the fascia panel Difficult/impossible to change a gear Lack of power Absence of automatic stopping of the internal combustion engine
Suspect Areas:	Frequent causes Selection sensor Other possible causes 12-way connector of the piloted manual gearbox ECU 12-way harness of the piloted manual gearbox ECU Controlled manual gearbox ECU

How old is the battery? IF older then 5 years it may be time to replace it. I would get a battery health check done as just because it starts, there may not be enough juice to supply all the electrical equipment on the vehicle. Also check the connections on the piloted gearbox, as this won't be the first time we've heard of this issue - often after it has had some maintenance done and somebody has knocked / unplugged or not connected a connector back up properly or bent a pin.

[Doo]

Hi
First time posting, couldn't find what I was looking for so started a new topic, I hope that's okay. If not please let me know the right place to post.
My c4 grand picasso semi auto.
Is stuck in Neutral and showing Gearbox Faulty in dash, car wont always start and when it does there is a pause and 3 knocks and when engine running but idle car feels very juddery
Diagbox shows P1734 Gearbox actuator position in the gear selection shaft signal fault-Short to Earth, permanent fault. I'm waiting for a new jack to arrive to check the acctuator fluid tank, but quick look through the engine bay, I think it may be empty. What could cause this? And could that bring up this fault or does it indicate something else is going on, if so any ideas what it could be? Please help

I recently changed the clutch on our car as the piloted box was playing up. It would start, jump forward & immediately stall. It did this every single morning... I went in with DiagBox & reset the system which helped for a few weeks, but when I removed the gearbox from the engine, it was clear what had caused the issue. The crankshaft oil seal had started leaking and the oil was contaminating the clutch. I assume the sensors picked up the difference in speed as the clutch would have been slipping in higher gears.

Anyway, I would suggest making sure the resevoir bottle is clean as mine was so dirty I couldn't tell what it was, let alone how full it was! Once clean, I found shining a bright torch through it to see the contents was very helpful. Ours was in fact full.

I replaced the clutch with a system kit from LUK and so far it has been excellent. It comes with the clutch plate, cover & replacement electro/hydraulic operated release bearing which was very simple to fit with the box on the bench (it is MUCH easier to drop the engine & box together out of the front of the C4 hatchback, but it means an extensive dismantle, not sure how epic it would be on your model, but I imagine a similar hilarity should you need to go down that route). I cleaned EVERYTHING so that the new components would go back together and function.

However, before you go down that particular rabbit hole, you will need to find your problem. If you have lost your oil, there has to be a cause. Either the plastic resevoir is split or the clutch release bearing has fallen apart and the fluid is in the box. Either way, there would be a trail of fluid... I think you would have noticed.

If there is a short circuit as the sensor has picked up, then that is almost always mechanically inflicted (something has cut the wire perhaps). It sounds like something is affecting the clutch release bearing.

Check you haven't run over something such as a sharp stone that might have got flung up into the front of the gearbox, damaging any wires or the gearbox ECU which is mounted on the front just above the resevoir. From memory, there are a few external sensors on the front of the box and one at the top rear. Check those wires too.

[Georgie712]

Thankyou so much for your replies
So I now have some more information
Car went to main dealer after automatic specialist wouldn't touch it cos it was semi auto and not full auto and local garage said it had to go to main dealer due to the code.
I had car towed there by breakdown cover, told them the code, paid £120 for diagnostic for them to tell me same error I already knew. They told me it was electrical fault and actuator needed replacing and quoted me over 2k to fix. I spoke to a mechanic I know who's fab and he said no way. Paid for car to be towed back home. He came n looked at it. The garage had tried to partly reprogrammed the gears and clutch throwing even more error codes in the way and mechanic said the car had been bled dry of gearbox oil and the car wouldn't pressurise or repressurise. He managed to resolve this and got the pump working again allowing the gers to shift but they won't engage sticking with the original fault I had. He has assured me that the actuator isn't the problem and truly believes the fault lies in either the gearbox ecu or the wiring to or from the gearbox ecu to actuator and said I need an auto electrician to repair. I've contacted loads of them and they all say its a gearbox issue and I need a gearbox specialist. Even though I've told them it's ecu/wiring/electrical and not the actual gearbox or actuator unit itself. I'm being pushed from pillar to post and going round n round in a vicious circle. I've currently spent over £600 fault finding, towing and replacing things like battery etc to be in a no better position than I was to begin with. Only place that's offered to help can't see me til 8th November. My MOT runs out 6th of October and I've nowhere to sorn the car. Please does anyone know what I can do? This is such an awful situation and I've never felt so stressed about something so trivial.

Location is West Norfolk, if anyone can help?
TIA

[Doo]

Thankyou so much for your replies
So I now have some more information
Car went to main dealer after automatic specialist wouldn't touch it cos it was semi auto and not full auto and local garage said it had to go to main dealer due to the code.
I had car towed there by breakdown cover, told them the code, paid £120 for diagnostic for them to tell me same error I already knew. They told me it was electrical fault and actuator needed replacing and quoted me over 2k to fix. I spoke to a mechanic I know who's fab and he said no way. Paid for car to be towed back home. He came n looked at it. The garage had tried to partly reprogrammed the gears and clutch throwing even more error codes in the way and mechanic said the car had been bled dry of gearbox oil and the car wouldn't pressurise or repressurise. He managed to resolve this and got the pump working again allowing the gers to shift but they won't engage sticking with the original fault I had. He has assured me that the actuator isn't the problem and truly believes the fault lies in either the gearbox ecu or the wiring to or from the gearbox ecu to actuator and said I need an auto electrician to repair. I've contacted loads of them and they all say its a gearbox issue and I need a gearbox specialist. Even though I've told them it's ecu/wiring/electrical and not the actual gearbox or actuator unit itself. I'm being pushed from pillar to post and going round n round in a vicious circle. I've currently spent over £600 fault finding, towing and replacing things like battery etc to be in a no better position than I was to begin with. Only place that's offered to help can't see me til 8th November. My MOT runs out 6th of October and I've nowhere to sorn the car. Please does anyone know what I can do? This is such an awful situation and I've never felt so stressed about something so trivial.

Location is West Norfolk, if anyone can help?
TIA

I'm confused... Gearbox oil lubricates the gears & final drive. If the car had no gear oil, it would grind and clonk and jump out of gear, etc.

Do you mean the fluid for the clutch actuator & electro valves that do the selecting?

I'd love to have a look at it, but unfortunately I'm wayyy oop north.

Marc has loaded the possibilities so the best thing is to try yourself. I know it wont be easy, but the print out mentions dead short so I would start at the wires on top of the battery. I believe there is a blue wire which can cause issues.

However, getting back to your original query, the lack of oil... I wonder if your problem is the return pipe to the actuator? They are apparently a common issue and this would explain the loss of fluid. The pipe is partly obstructed by the gearbox ECU which is attached to the front of the gearbox. Look for an oily mess in this vicinity and I guess the real issue may well lie there. I suspect the short circuit is either a separate issue, or created by the lack of fluid....

[Georgie712]

Thanks Doo, I thought the actuator fluid tank was empty, it wasn't when it went to citroen as they told me it was fine, however, when it came back it was, or so my mobile mechanic said, so he filled it so the tank could be pressurised, there is no leak to the tank. So that's all fine.
However car still showing short to earth. Citroen says new gearbox ecu is required as the fault is electrical-short to earth inside of this. But recommend I replace the whole unit. Does anyone know if the part numbers need to match? I'm trying to find a used one, or is it just years need to match. My car is 2009 and my ecu/actuator part number is 9664870880.
Do I need to find one with that number on?
Thanks

[Doo]

Thanks Doo, I thought the actuator fluid tank was empty, it wasn't when it went to citroen as they told me it was fine, however, when it came back it was, or so my mobile mechanic said, so he filled it so the tank could be pressurised, there is no leak to the tank. So that's all fine.
However car still showing short to earth. Citroen says new gearbox ecu is required as the fault is electrical-short to earth inside of this. But recommend I replace the whole unit. Does anyone know if the part numbers need to match? I'm trying to find a used one, or is it just years need to match. My car is 2009 and my ecu/actuator part number is 9664870880.
Do I need to find one with that number on?
Thanks

I'll be honest, Marc would be the best person to ask. However, when we thought our BSM was faulty. Found one with matching numbers and all was well. So I can't see why it wouldn't apply to the gearbox unit too...

[machinedred]

Any updates on this ,I've same code and desperate for help . Thanks . Bob

[GiveMeABreak]

The fault code descriptor is in my previous post above. That should provide pointers.

[machinedred]

Thanks Marc , what is the cheapest way I can get software to read box data ? I swopped the actuator block as it was an easy job and it drove fine for 5 mins then I lost drive and the dash was flicking between 1and 2 gear i tried to get out and push the car and it felt like the brakes were stuck on i had to rock it back and forth and then it started rolling ( deffo brakes not a gearbox brake as I had no backlash in CVjs as I was rocking it ) I managed to push it home and then I selected reverse it didn't move until I have it a good rev and then it jumped backwards and then allowed me to use paddles to move it about. As I say I need to read what's going on but my XTool just says n/a on all items when I access the box

[GiveMeABreak]

It really needs Diagbox with a Lexia 3 VCI to read the codes properly. These semi Autos are basically manual gearbox and clutches with hydraulic actuators to do the gear changes and as such they can have a myriad of issues, so really do need a proper diagnostic. Repairs can be expensive, so always better to have the fault properly diagnosed.

[Otaru]

Hi. I've been having problems with the same. I'm getting the same error codes, particularly 3 of them:

P0944
P1731
P1749

The symptoms in my car are: sometimes when starting to drive from stop position, suddenly it's like the 1st gear disengages abruptly. Apart from that, while driving on 3rd or 4th gear, when I release the throttle, there is a noise probably coming from the gearbox, a kind of "canned" sound of something metallic. It sounds like gears are not having good contact while running.

What I have already done: I changed the gearbox oil, the activator oil, and the accumulator (black ball). Still happens

I don't know what else to do.