Citroën C3 U1209 – Communication fault with gearbox ECU

[Memo6161]

Hello everyone,

I have a 2011 Citroën C3 1.4 petrol with a robotised manual (BVMP/SensoDrive) gearbox.

I am getting the following fault:

U1209 – Communication with the transmission control unit: Invalid data received.

This fault is stored in the ABS/ESP ECU.

I can communicate with the gearbox ECU using the diagnostic tool, and there are no fault codes stored in the gearbox ECU itself. I can also access the live data.

However, in the gearbox ECU live data, the starting authorization shows:

“Not activated – Starting not authorised.”

I have checked the CAN wiring between the gearbox ECU, ABS/ESP ECU and engine ECU, and I have continuity between them.

I believe there may be a broken or damaged wire somewhere in the CAN wiring, but I am not sure which section I should focus on.

According to the wiring diagram, the CAN lines between the ABS and gearbox ECU join together and then go to the engine ECU, and I have checked this section and it appears to be good.

I have also checked the CAN lines between the ABS ECU and the BSI, and these also appear to be good.

So what I am wondering is: which CAN wiring section should I check next? Could there be another splice or connection point that could cause the U1209 fault?

Could the gearbox ECU itself have an internal CAN communication fault even though I can communicate with it normally using the diagnostic tool and there are no faults stored inside the gearbox ECU?

What would you recommend checking next?

Thanks in advance for any advice.

[Memo6161]

At the very least, could someone send me the wiring diagram for the ABS or transmission ECU?

Any help would be greatly appreciated.

[ozvtr]

If you are asking for internal circuit diagrams for the ABS and/or gearbox ECUs, there aren't any to my knowledge.
It seems that you have a circuit diagram for the car, so that's the best that you will do.
Doesn't make sense that there is a coms error with the gearbox ECU but you can still poll the gearbox ECU?
I could only assume that the ABS module was trying to pass information on the the gearbox ECU but it didn't answer?

However, in the gearbox ECU live data, the starting authorization shows:
“Not activated – Starting not authorised.”

Did you have your foot on the brake and the ignition on when you polled the gearbox ECU? It might be locked out simply because it wasn't ready to start.
Does the car start and run?
Have you tried resetting the gearbox ECU? Have you tried clearing the U1209 DTC?
Has the car done any other strange things lately? Any other DTCs?

[Memo6161]

Yes, I had my foot on the brake and the ignition was on when I connected to the gearbox ECU. I even replaced the brake pedal switch.

I think the U1209 fault is preventing the car from becoming ready to start.

When I switch the ignition on, N is displayed and the gearbox recognises the gears. I can also see this in the live data. However, the car does not crank/start by itself. If I manually activate the starter motor and get the engine running, the gearbox then goes into limp mode.

Regarding resetting the gearbox ECU, if you mean disconnecting the battery, I have already tried that.

I cannot clear the U1209 fault at all. It is a permanent fault.

The only other fault code I have is 0994 – A/C compressor clutch fault.

Thank you very much for your interest and help. I really hope we can solve this problem.

[RichardW]

If you look at the live data in the ABS ECU is there anything that looks out of place relating to the gearbox?

[Memo6161]

I only had a quick look at the live data and didn’t specifically focus on the gearbox-related values. Is there a particular submenu or specific parameters you would like me to check? I can take a closer look and send you screenshots.

[Memo6161]

1. System Identification

Supplier: TEVES
PSA Reference: 9665375680
Additional Number: 9674415980
Software Version: 255.255
Calibration Version: 255.255
Messaging Index: Q

ECU Information:
00–100a–02(-1)–2d07-559-ESPMK60_O
9665375680_9674415980_744398

⸻

2. Data Stream

Engine Speed: 0 rpm
Front Left Wheel Speed: 0 kph
Front Right Wheel Speed: 0 kph
Left Rear Wheel Speed: 0 kph
Network Communication Diagnostics: Dialogue Problem
Right Rear Wheel Speed: 0 kph
Supply Voltage: 8.59 V
Transverse Acceleration: 0.66 ft/s²
Vehicle Speed: 0 kph

⸻

3. Data Stream

Accelerator Pedal Position: 0 %
Actual Torque: -16.24 lb-ft
Anti-slip Regulation / Motor Skid Regulation (MSR) Setting Performance Status: Normal Operation
Change Of Gear In Progress: NO
Engine Speed: 0 rpm
Gearbox Gear Engaged: Not Available
Gearbox Torque Converter Status: Unspecified Value
Status Of The Clutch: Unspecified Value
Torque Required By The Driver: [ekranda devamı görünmüyor]

⸻

4. Data Stream

Adjustment Of The Steering Wheel Angle Sensor: Adjusted
Calibration Of The Steering Wheel Angle Sensor: Calibrated
Direction Of Steering Wheel Rotation: Left
Steering Wheel Angle: -349 deg
Steering Wheel Angle Sensor Status: Good Condition

⸻

5. Diagnostic Trouble Code

U1209

Fault: Absence Of Communication With The Automatic Gearbox ECU. Data Invalid

Permanent Fault

⸻

6. Data Stream

ABS/ESP Deactivation Switch: Deactivation Of ABS/ESP Not Required
Brake Fluid Level: Sufficient
Brake Lamps Switch: Pressed
Brake Linings Wear: Not Worn
Braking Pressure: 0.6 bar
Control Unit Supply Voltage: 8.52 V
Electrovalve Supply Relay Status: Normal Operation
*Secondary Brake Lights Switch 1 (If Cruise Control Fitted): Pressed

[RichardW]

Steering on almost full left lock?

Supply voltage under 9V

Brake pedal was pressed?

Those are the things that jump out as potentially being an issue - particularly the voltage.

[Memo6161]

Yes, the brake pedal was pressed because I was pressing it to show that it was working.

The voltage also caught my attention. The battery is currently around 13 V. Could there be a problem with the power supply to the ABS/ESP ECU?

What should I check or do to get the voltage back to the normal level?

[Memo6161]

Do you happen to have the wiring diagram or pinout for the ABS connector? I’m not very experienced with this kind of electrical diagnosis, so I’m not sure where exactly I should check the power supply.

[ozvtr]

Regarding resetting the gearbox ECU, if you mean disconnecting the battery, I have already tried that.

No.
To reset the gearbox ,
1) key off, remove key.
2)Close all the doors and tail gate but open the bonnet.
3)Wait no less than 60 seconds.
4)Disconnect the battery positive. Leave it disconnected for a minute or two (the time is not critical).
5)Reconnect the battery positive. Wait no less than 60 seconds.
6)Open the door, get in, turn ignition switch to first position, accessories . See if gear indicator shows "-". If NOT go back to the beginning try again. Gear indicator MUST indicate "-"!!
7)When the gear indicator shows "-", press on the brake peddle AND HOLD IT THERE!!
8)Rotate key to second position, ignition (on..NOT START! do not start the car). If you got everything right, the gearbox will "click and "clack" for about 30 seconds. DO NOT TAKE YOUR FOOT OFF THE BRAKE DURING THIS TIME!! When the gearbox is done it will show a gear number or "N" on the display. You can take your foot off the brake, it's done.

[Memo6161]

2011 Citroën C3 Exclusive, automatic, 95,000 km, with 1 year of TÜV remaining.

The vehicle currently has a U1209 fault code, which I have not been able to diagnose. The engine and gearbox are otherwise normally fault-free.

When the ignition is switched on, the gearbox engages N, 1 and R normally. However, the engine will not start using the ignition key.

The engine can be started directly via the starter motor for testing purposes. When started this way, a “–” (dash) appears on the gear display.

The car is located in Mannheim, Germany.

Price: €2,000.

If anyone is interested or has experience diagnosing this type of fault, feel free to contact me.

[Paul-R]

@Memo6161

Are you offering the C3 for sale as a project with this fault? I am unsure.

[Memo6161]

Yes, exactly. I am offering it for sale as a project with the U1209 fault. The car is otherwise in good condition, but I have spent enough time trying to diagnose the issue and no longer want to continue with it.

[Paul-R]

Can I suggest you copy and paste that post into a fresh post in the Free, For Sale & Wanted section? viewforum.php?f=7