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Citroen C5 X7 2011 LED License Plate Lighting Issue: Not Turning On Automatically, Allegro Purchase

Gomes 40 5775 15
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  • #1 17127732
    Gomes 40
    Level 10  
    Posts: 17
    Rate: 10
    Hello, I want to ask. My car is Citroen C5 X7 2011.
    I bought LED lamps to illuminate the register plates. from this auction from Allegro:
    / LED-array-Citroen-c2-c3-c4-c5-c6-berlingo-DS3
    Moderated By Mirek Z.:

    I removed part of the link to the auction - https://www.elektroda.pl/rtvforum/faq.php p. 3.1.18.


    The lamps are nice, but I have a problem. The backlight does not turn on automatically when the engine is started. In order for it to light up, I have to turn the lamp switch to " 0 "and again on" car ".
    I bought them about two weeks ago and made a complaint. The seller sent me a new set again. New llamas that arrive behave identically.
    I connected the original factory lighting with bulbs and there is no problem with them.
    Anybody knows what's going on?
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  • #2 17127805
    DiZMar
    Level 43  
    Posts: 32219
    Help: 2869
    Rate: 6508
    Does the voltage on the LED appear after starting the engine? If you cannot measure, connect LEDs and a traditional bulb in parallel. After starting the engine, what lights up?
  • #3 17127826
    Gomes 40
    Level 10  
    Posts: 17
    Rate: 10
    After starting the engine, there is a short flash and they go out.
  • #4 17127833
    koks110
    Level 10  
    Posts: 64
    Rate: 11
    And ordinary light bulbs used to glow normally before? Check if there is still voltage after firing on the wire, if so, something must be wrong with the led lights.
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  • #5 17127841
    DiZMar
    Level 43  
    Posts: 32219
    Help: 2869
    Rate: 6508
    Gomes 40 wrote:
    After starting the engine, there is a short flash and they go out.

    Does the voltage remain and the LEDs are off? Without a meter, you can check it with an ordinary light bulb. If the voltage remains, it is the fault of the LEDs. If not, and it appears only after the car's computer is turned off / on.
  • #6 17127854
    Gomes 40
    Level 10  
    Posts: 17
    Rate: 10
    Yes, I wrote above that I connected the factory lamps with bulbs and they shine correctly.
    I have the impression that the computer senses the LEDs and disconnects them.

    Added after 1 [minutes]:

    Tomorrow I will measure the voltage with the leds connected.
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  • #7 17127861
    Krzysztof Kamienski
    Level 43  
    Posts: 21874
    Help: 2030
    Rate: 5128
    The light controller detects too low current consumption in the lighting circuit. Nominally, two 5W bulbs are 10W, that is ~ 0.8A. And LEDs? Less than half of that.
  • #8 17127868
    DiZMar
    Level 43  
    Posts: 32219
    Help: 2869
    Rate: 6508
    Krzysztof Kamienski wrote:
    The light controller detects too low current consumption in the lighting circuit. Nominally, two 5W bulbs are 10W, that is ~ 0.8A. And LEDs? Less than half of that.

    Why the LEDs consume less electricity. The linked auction is
    Quote:
    CAN-BUS system - no burnt bulb error messages

    The driver should be "cheated" by LED lamps.
  • #9 17127869
    Gomes 40
    Level 10  
    Posts: 17
    Rate: 10
    It's just like DiZMar wrote earlier, if I connected the light bulbs in parallel, it should be ok.
  • #10 17127876
    koks110
    Level 10  
    Posts: 64
    Rate: 11
    The lights are probably without can and the computer can probably see the burnt bulb and turn off the power on them. You will need to replace the leds with stronger ones or add a condenser.
  • #11 17127882
    DiZMar
    Level 43  
    Posts: 32219
    Help: 2869
    Rate: 6508
    Gomes 40 wrote:
    It's just like DiZMar wrote earlier, if I connected the light bulbs in parallel, it should be ok.

    If this is the case, however, contrary to what I wrote, the fault may be on the LED side - they do not pretend to be light bulbs sufficiently. They do not "cheat" the driver in the car.
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  • #12 17128759
    Marian B
    Level 38  
    Posts: 3479
    Help: 389
    Rate: 1154
    And here is the problem that in the case of CAN control, it makes no sense to use LED instead of bulbs, because you need to ensure adequate power consumption by this LED bulb by adding, for example, a resistor, which does not make sense at all, because LED is used to save electricity . Using an LED and an additional resistor pretending to be a light bulb? A bit nonsense.
    An imposing solution is simply a separate power supply for the LED. Actually, it is only one wire, because the mass already exists.
  • #13 17129217
    mariann
    Level 39  
    Posts: 3450
    Help: 544
    Rate: 637
    Hello
    koks110 wrote:
    or add a condenser


    I know about adding a resistor and how it works, but how does a capacitor help in this case and how should it be turned on?
    Best regards.
  • #14 17129483
    koks110
    Level 10  
    Posts: 64
    Rate: 11
    mariann wrote:
    Hello
    koks110 wrote:
    or add a condenser


    I know about adding a resistor and how it works, but how does a capacitor help in this case and how should it be turned on?
    Best regards.


    Sorry, my mistake, it was supposed to be a resistor, something else I thought and wrote something else.
  • #15 17130303
    Gomes 40
    Level 10  
    Posts: 17
    Rate: 10
    Thanks to everyone for your help.
    I will be looking for other lamps. :cry:
  • #16 17131104
    Szyszkownik Kilkujadek
    Level 37  
    Posts: 5011
    Help: 211
    Rate: 1008
    @gomes 40 give it a rest and put them there, as provided by the manufacturer. By inserting LEDs in place of light bulbs, you risk even losing the registration certificate for a broken vehicle.
    PS
    One word:
    Gomes 40 wrote:
    I plugged

    Gomes 40 wrote:
    rozłancza

    Gomes 40 wrote:
    connected

    Gomes 40 wrote:
    podłąnczył

    and so many "varieties" :-D
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Topic summary

✨ The discussion revolves around a lighting issue with LED license plate lamps installed in a 2011 Citroen C5 X7. The user reports that the LED lights do not turn on automatically when the engine starts, requiring manual intervention to activate them. Responses suggest that the vehicle's computer may be detecting insufficient current draw from the LEDs compared to traditional bulbs, leading to the lights being turned off. Various solutions are proposed, including checking voltage levels, using resistors to simulate the load of standard bulbs, and considering the use of stronger LEDs or capacitors to ensure proper functionality. The user expresses intent to seek alternative lamps after receiving multiple sets with the same issue.
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FAQ

TL;DR: In a Citroën C5 X7, the controller expects ~0.8 A from two 5 W bulbs; "The light controller detects too low current consumption." CANBUS LEDs can flash once and switch off; fix by adding load, testing in parallel, or reverting to bulbs. [Elektroda, Krzysztof Kamienski, post #17127861]

Why it matters: This FAQ helps Citroën C5 X7 owners fix LED license plate lights that don’t auto‑turn‑on after engine start.

Quick Facts

Why do my Citroën C5 X7 LED license plate lights flash then turn off?

The body control module monitors current on the plate light circuit. OEM uses two 5 W bulbs, about 10 W total. That’s roughly 0.8 A expected. Your LEDs draw far less. The controller interprets this as a failed bulb and cuts power. "The light controller detects too low current consumption." [Elektroda, Krzysztof Kamienski, post #17127861]

How can I confirm if the circuit still has power after startup?

Use a standard bulb as a test load. Connect it to the plate light wires or in parallel with the LEDs. If the bulb stays lit after start, power is present, and the LED module is at fault. If it goes off, the controller shut the circuit down. Without a meter, this is the quickest diagnostic. [Elektroda, DiZMar, post #17127841]

Will switching back to factory bulbs solve this?

Yes. The OP refitted the factory lamps with bulbs, and they worked correctly. That confirms the car and wiring are fine. The issue lies with the LED modules or their CAN emulation. Returning to OEM bulbs keeps the automatic behavior without errors. [Elektroda, Gomes 40, post #17127854]

Do “CANBUS” LEDs guarantee no errors on the C5 X7?

No. Some “CANBUS” kits still fail to mimic the load that the controller expects. As one expert noted, they “do not pretend to be light bulbs sufficiently. They do not ‘cheat’ the driver.” Choose products with proven PSA compatibility and a return option. [Elektroda, DiZMar, post #17127882]

How do I verify if my “CANBUS” LEDs are actually compatible?

Do a parallel‑bulb test. Connect a standard bulb in parallel with the LED module. Start the engine and observe. If the combined load keeps the circuit on, your LED’s emulator is inadequate. Replace with a better‑specified module or add a resistor if you accept the heat and power loss. [Elektroda, DiZMar, post #17127805]

Could a capacitor fix the error instead of a resistor?

No. A capacitor does not provide steady current draw for bulb‑out monitoring. The suggestion to use a capacitor was corrected in the thread. “Sorry, my mistake, it was supposed to be a resistor.” Use resistive load if you choose that route. [Elektroda, koks110, post #17129483]

Is adding resistors a good long‑term solution?

It works, but it defeats the point of LEDs and adds heat. You end up wasting power to mimic the bulb load. As one member put it, “Using an LED and an additional resistor... A bit nonsense.” Consider an alternative supply or LEDs that truly match the expected load. [Elektroda, Marian B, post #17128759]

How do I perform the bulb‑in‑parallel test safely?

  1. Disconnect the LED and identify the plate light positive and ground.
  2. Connect a standard bulb holder in parallel with the LED’s connectors.
  3. Start the engine and check which light stays on; note the result. This quickly shows whether the circuit or the LED is at fault. [Elektroda, DiZMar, post #17127805]

Is a wiring fault likely here?

Unlikely, given the evidence. With factory bulbs installed, the plate lights operate normally. That indicates good wiring and power supply. The failure appears only with the LED modules, implicating their design or load characteristics. [Elektroda, Gomes 40, post #17127854]

Why does toggling from “0” to “Auto” make the LEDs light, then fail again?

Switching resets the light circuit in the controller, so the LEDs light briefly. The OP reports it lights only after toggling, not automatically. This behavior aligns with low‑current shutdown of monitored circuits. [Elektroda, Gomes 40, post #17127732]

What current does the C5 X7 plate light circuit expect?

About 0.8 A total. “Nominally, two 5 W bulbs are 10 W, that is ~0.8 A. And LEDs? Less than half of that.” That difference triggers the controller’s bulb‑out logic. [Elektroda, Krzysztof Kamienski, post #17127861]

What if my replacement LEDs flash once and both sets act the same?

Assume a compatibility issue with the built‑in emulator. The OP received a second set, and it behaved identically. Return them and choose another design or approach. Reputable sellers list compatibility with Citroën/PSA CAN systems. [Elektroda, Gomes 40, post #17127732]

Are there legal concerns with LED plate lights on this model?

Yes. A forum member warns that fitting LEDs in place of approved bulbs risks a failed inspection. “By inserting LEDs in place of light bulbs, you risk even losing the registration certificate.” Confirm homologation before modifying lighting. [Elektroda, Szyszkownik Kilkujadek, post #17131104]

Can I power the LED modules from a separate feed to avoid errors?

Yes, if you know what you’re doing. One member suggests a dedicated supply so the LED isn’t on the monitored circuit. “An imposing solution is simply a separate power supply for the LED.” Ensure proper fusing and routing. [Elektroda, Marian B, post #17128759]

What’s the simplest, safest fix today?

Reinstall OEM bulbs or a homologated equivalent. This restores automatic operation with no errors and avoids legal risk. As another member put it, “give it a rest and put them there, as provided by the manufacturer.” Save LEDs for models designed for them. [Elektroda, Szyszkownik Kilkujadek, post #17131104]
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