Gearbox faulty

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Mhamilton
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Gearbox faulty

Post by Mhamilton »

Hi all
I’m having issues with my grand c4 2007 exclusive 2.0 petrol egs 68000
It’s thrown up faulty gearbox On the dash can’t select gears and shows 2 But no drive regardless of what i do.
Once the engine is warmed up I can turn the engine off let Ecupower down for a minute then it will start and select gears and Gives me drive
I can then go to it later the same day With engine cold and starts and drives as should. Have checked and cleaned all Electrical connections and Checked actuator reservoir and pipe work and all appears to be correct I get intermittent p1726 fault as well
I’m located north norfolk any help or ideas most appreciated

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GiveMeABreak
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Re: Gearbox faulty

Post by GiveMeABreak »

There are a stack of possible fault codes for these - so really we need a fault code to provide any guidance. If you can get it read with a Lexia / Diagbox it will give you some pointers.

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

Only code that shows up on my code reader is the one above and I haven’t got lexia I’m looking at getting it though

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

Code is p1726 is all my code reader brings up

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GiveMeABreak
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Re: Gearbox faulty

Post by GiveMeABreak »

Ok, so Pop your VIN up when you get the chance so I can check exact system and engine, but for this fault:

P1726: Fault with the signal for the position of the gearbox actuator in the gear engagement shaft: Short circuit to earth. The voltage of the signal is lower than 0,4 V and the time of appearance of the fault code is 1s.

The fault will appear when:The following conditions have to be met:
- Ignition on
- The starter motor is not operating
- Absence of gear changing

Down Grade Modes Present whilst the Fault is Active:
1) 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 the vehicle has the Stop and Start system : Stop and start function deactivated

2) Engine stopped and not in Stop and Start phase
- Gear change prohibited (until the ignition is switched off)
- Request for neutral via the lever is achieved through opening of the clutch
- The engine can be started

Warnings / Messages:

"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

Symptoms: Difficult/impossible to change a gear, Lack of power, Absence of automatic stopping of the internal combustion engine.

Suspect Areas: Gear engagement sensor
12-way connector of the piloted manual gearbox ECU
12-way harness of the piloted manual gearbox ECU
Controlled manual gearbox ECU

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

Cool thank you where is the gear engagement sensor located
Vin number is VF7**************[VIN obfuscated, can be read by forum staff]

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GiveMeABreak
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Re: Gearbox faulty

Post by GiveMeABreak »

There are 2 sensors:

(10) Gear engagement position sensor.
(11) Gear selection position sensor.
C4 Picasso Gear Sensors.PNG
So I'd certainly be checking the connections to these as a precursor to any further investigation.

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

Many thanks I’ve cleaned up all connections and still got same fault code plus now got p1734 any suggestion

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GiveMeABreak
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Re: Gearbox faulty

Post by GiveMeABreak »

That issue is to do with the piloted manual gearbox.

P1734 means there is a short circuit to earth fault with the signal of the position of the gearbox actuator in the gear selection shaft. The voltage of the signal is lower than 0.5V.

Downgrade modes with the engine running:
- 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

Downgrade modes with 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:

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


It's going to take some investigation to be honest - checking the wiring connections to determine whether the sensor is at fault or the wiring to the sensor.

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

I’m hoping it’s wiring it’s now not selecting gear regardless of what I do

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

Engine still running can hear actuators clicking on start up but won’t select

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

Engine still running can hear actuators clicking on start up but won’t select

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GiveMeABreak
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Re: Gearbox faulty

Post by GiveMeABreak »

That's what the downgrade mode is doing - reverting to Neutral or preventing gears from being selected.

Mhamilton
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Re: Gearbox faulty

Post by Mhamilton »

Is there anyway you can trick it into thinking that the sensors are working
Can’t find any breaks in wires as of yet

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GiveMeABreak
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Re: Gearbox faulty

Post by GiveMeABreak »

No - because it is a safety feature by design. You would not want the car jumping into gear on it's own or that could be disastrous.

These boxes can be a curse - you may need to bite the bullet and get it to a dealer given that it is immobile now - as even if you tries replacing one or both of the sensors, they you still need to programme the gearbox gate using Lexia.