FAQ
TL;DR: Peugeot 407 SW rear-left indicator faults often trace to 1 failed BSI output; “I located on the black 3-pin plug.” [Elektroda, Aleksander_01, post #16936886]
Why it matters: This FAQ helps 2004–2010 Peugeot owners quickly diagnose BSI B4BD turn-signal errors without chasing the entire loom.
Quick-Facts
- Rear-left turn feed identified as A17 287C wire to lamp cluster. [Elektroda, Daro122, post #16936339]
- Related connector noted as a black 3‑pin plug at the BSI area. [Elektroda, Aleksander_01, post #16936886]
- Code B4BD = “short to rear left turn signal” reported by scan tool. [Elektroda, Aleksander_01, post #16934200]
- Battery clamp pull can restore function temporarily, sometimes for over 30 minutes. [Elektroda, Aleksander_01, post #16934332]
- Burned lamp-ground (“mass”) fixed by adding a direct ground wire to the board. [Elektroda, Aleksander_01, post #16934396]
Quick Facts
- Rear-left turn feed identified as A17 287C wire to lamp cluster. [Elektroda, Daro122, post #16936339]
- Related connector noted as a black 3‑pin plug at the BSI area. [Elektroda, Aleksander_01, post #16936886]
- Code B4BD = “short to rear left turn signal” reported by scan tool. [Elektroda, Aleksander_01, post #16934200]
- Battery clamp pull can restore function temporarily, sometimes for over 30 minutes. [Elektroda, Aleksander_01, post #16934332]
- Burned lamp-ground (“mass”) fixed by adding a direct ground wire to the board. [Elektroda, Aleksander_01, post #16934396]
What does BSI error B4BD mean on a Peugeot 407?
B4BD indicates a detected short circuit on the rear-left turn-signal circuit. The symptom is a dead left indicator and stored BSI fault. [Elektroda, Aleksander_01, post #16934200]
Which BSI wire feeds the rear-left turn signal?
Users identified the rear-left indicator feed as wire A17 287C that runs from the BSI to the left rear lamp cluster. [Elektroda, Daro122, post #16936339]
Where is the connector for this circuit on the BSI?
One repair located the relevant lead on a black 3‑pin plug at the BSI. The output “driver” for that bulb had failed. [Elektroda, Aleksander_01, post #16936886]
Will disconnecting the battery reset the indicator fault?
A battery disconnect can temporarily restore the indicator. "Disconnect the battery for a while." Then retest the circuit. [Elektroda, andrzej20001, post #19303495]
How long should I leave the battery disconnected?
One member tried up to 4 hours with no lasting fix. If the fault returns, the issue isn’t reset-related. [Elektroda, Nas19, post #19306528]
Can swapping left and right indicator feeds help diagnose?
Yes. Swap mux/feeds to compare left vs right. If the fault follows the lamp, suspect the lamp/ground; if not, suspect wiring/BSI. [Elektroda, Anonymous, post #16934242]
What if the lamp ground (“mass”) pad is burnt?
Add a dedicated ground wire soldered from harness ground to the lamp board. This restored function in similar cases. [Elektroda, Aleksander_01, post #16934396]
What is the “driver” people mention in this thread?
It’s the BSI’s output stage for the bulb. One case found that driver "released" (failed) for the left rear circuit. [Elektroda, Aleksander_01, post #16936886]
Could a short inside the BSI be the cause?
One responder noted if the BSI itself shorted, the bulb behavior and ground fault message wouldn’t match that scenario. [Elektroda, Anonymous, post #16934347]
Why does a battery reset help only briefly?
Reset clears a latched fault, but hazards work without ignition. Intermittent wiring or lamp issues can quickly retrigger the code. [Elektroda, Anonymous, post #16934734]
How do I perform a quick 3‑step BSI reset for the indicators?
- Switch everything off and open the hood.
- Disconnect the battery negative clamp and wait a short while.
- Reconnect, then test indicators and hazards.
"Disconnect the battery for a while." [Elektroda, andrzej20001, post #19303495]
Only the rear-left lamp is dead—what next?
If ground is good and bulb is new, suspect the BSI output for that circuit. One fix required replacing that BSI driver. [Elektroda, Aleksander_01, post #16936886]
Is there an inline module between BSI and the rear lamp?
The thread’s working fix targeted the BSI output and the A17 287C run, not a separate inline module. [Elektroda, Daro122, post #16936339]
What’s an edge case that can confuse diagnostics?
A lamp can still shine yet log a ground short. Check for partially burned ground paths on the lamp board. [Elektroda, Anonymous, post #16934347]
What real-world duration did the reset last?
After pulling the clamp, the indicator worked again, sometimes for over half an hour before failing. [Elektroda, Aleksander_01, post #16934332]
