2016 Peugeot 508 GT 2.0 BlueHDi – B1624/B162C CPC Relay Fault, BPGA Tested Good, Suspect BSI/Wiring

[vimal246]

Hi all,

Looking for specialist PSA/Peugeot electrical diagnostics input before I go too far down the wrong path.

Vehicle:
2016 Peugeot 508 GT 2.0 BlueHDi 180 (DW10FC / AHW engine)
VIN: VF3**************[VIN obfuscated, can be read by forum staff]

Issue:
Persistent “Electrical fault: have the vehicle repaired” warning with SERVICE light.

Main DiagBox faults:
- B1624 73 – Supplies protection and management unit: Central power switch positive relay status fault
- B162C 11 – Accessories positive relay control/status incoherent
- previously also B1601 15 (CPC relay control fault)
- U1218 81 communication fault with BSI / invalid data (gearbox ECU)
- exterior temp sensor fault (currently reading nonsense values like 87.5°C)
- historic keyless / hands-free faults (door handle sensors not working for a long time before this issue)

Important timeline:
The B1624 fault appeared suddenly. The faulty keyless door sensors existed long before this event, so I do not think they triggered it.

What has already been done:
- BPGA replaced with identical OEM used unit (same PSA part number, same fuse layout/ratings)
- New Varta AGM battery fitted
- Previous low battery episode before this issue (car driven with weak battery for some time)
- Radiator fan relay previously replaced

Key observations:
- Car starts every time
- Headlights, windows, radio, accessories all work
- Random intermittent “key not detected” happened at times
- Charging voltage healthy (~14.3–14.4V)

Multimeter testing performed:
Ignition ON, engine OFF:

Battery:
12.45V

BPGA main input:
12.45V

Voltage drop between BPGA input and multiple switched outputs:
0V

This strongly suggests:
- CPC relay IS electrically closing
- main BPGA power path is conducting properly
- outputs are live

DiagBox live data also shows:
- BSI command to CPC relay = ACTIVE
- BPGA relay status = CLOSED

This makes me question whether the BPGA was ever actually the root cause, especially since the original unit had the same B1624.

Current suspicion:
- BPGA ↔ BSI low-current control / feedback wiring issue
- BSI relay status monitoring/input fault
- BSI sleep/wake logic issue
- possible BSI fuse / supply issue

Questions for PSA specialists:
1. On the 508 R8 platform, what exact wires in the BPGA small low-current connector correspond to CPC command / feedback?
2. Has anyone seen B1624/B162C caused by BSI rather than BPGA?
3. Can a failed BSI internal input/logic circuit falsely report relay incoherence while BPGA is actually functioning?
4. Any known wiring break points between BPGA and BSI on this platform?
5. Could U1218 invalid BSI data be a symptom of the same root issue?
6. Any known BSI fuse(s) specifically worth checking for CPC monitoring logic?

I have ServiceBox wiring for the car and can test further with multimeter/DiagBox.

Appreciate input from anyone with real PSA electrical diagnostic experience.

[mickthemaverick]

I have moved this post to the Diagnostics area where you have a better chance of some help. Good luck