FAQ
TL;DR: 5 A OBD feed failures are common; "The 5a fuse located on the strip next to the battery was responsible..." Replace that 5 A fuse to restore scanner power. [Elektroda, Mlerte, post #17230644]
Why it matters: For Citroën C4 Grand Picasso owners and techs, this restores OBD power so diagnostics and coding work again.
Quick Facts
- Typical OBD2 pin 16 voltage ≈ 12 V; readings near 0.2 V indicate a supply fault. [Elektroda, radoslawdojlidko, post #20534981]
- Common fix: replace the 5 A fuse on the battery-mounted strip to restore OBD power. [Elektroda, Mlerte, post #17230644]
- Check F4 (10 A) in the board box, battery F2 and F5, and engine-bay F13 for OBD power feed. [Elektroda, korsarz50, post #20532914]
- BSI green 16‑pin connector, pin 2, provides the OBD pin 16 feed. [Elektroda, Maliniaktg, post #20536840]
- Fuse layouts differ between manual and automatic gearboxes; verify the correct map. [Elektroda, korsarz50, post #20532914]
Where is the OBD2 fuse on a Citroën C4 Grand Picasso?
On many C4 Grand Picasso cars, the OBD feed runs through a 5 A fuse on the battery-mounted strip. Owners report replacing this 5 A fuse restored OBD power. Inspect the strip next to the battery and identify the 5 A position. Replace it with the correct rating if blown. [Elektroda, Mlerte, post #17230644]
What voltage should be on OBD2 pin 16?
Pin 16 should show battery voltage, about 12 V, with the ignition on or off. Readings near 0.2 V indicate a failed feed. Measure between pin 16 and chassis ground. If low, proceed to fuse and BSI checks. [Elektroda, radoslawdojlidko, post #20534981]
Which fuses should I check if the OBD port has no power?
Check these in order: interior F4 (10 A) in the board box, battery-strip F5 (5 A), battery F2, and engine-bay F13. Some cars leave certain slots empty. Replace only blown fuses with correct ratings. This set feeds the OBD power path. [Elektroda, korsarz50, post #20532914]
How do I quickly troubleshoot no power on the OBD socket?
- Probe OBD pin 16 for voltage at the socket.
- Inspect engine-compartment fuse F5 in the feed path.
- Back-probe the BSI green plug, pin 2; confirm it outputs power to pin 16.
[Elektroda, Maliniaktg, post #20536840]
Where is the interior fuse strip relative to the OBD socket?
"Next to the OBD socket you have a fuse strip and a BSI with fuses." Inspect that area when diagnosing power loss. Loose add-ons or non-factory connections may also be present there. [Elektroda, pepe150, post #17170598]
My meter shows ~0.2 V on pin 16. What does that mean?
It indicates a nearly open circuit or high resistance to the OBD feed. Expect roughly 12 V at pin 16 in a healthy circuit. Check the battery-strip fuses and the BSI pin 2 output next. [Elektroda, radoslawdojlidko, post #20534981]
Does gearbox type change which fuse feeds the OBD port?
Yes. Manual and automatic transmissions use different fuse allocations. Confirm your vehicle’s fuse map before testing or moving fuses. This prevents misdiagnosis and saves time. [Elektroda, korsarz50, post #20532914]
Could a previous owner have fitted an OBD power switch?
Yes. A retrofit switch or altered feed can interrupt OBD power. Inspect for non-factory wiring or switches near the socket and fuse strip. [Elektroda, pepe150, post #17170598]
How do I confirm the BSI supplies power to the OBD port?
Find the BSI’s green 16-pin plug. Pin 2 should carry the OBD feed. If pin 2 has power but pin 16 does not, the harness or connector is at fault. [Elektroda, Maliniaktg, post #20536840]
Is there a fuse map for 2008–2012 C4 Grand Picasso?
Yes. A shared image lists BSI, BSM, and battery-strip fuses for 2008–2012 cars. Use it to confirm F2, F5, and F13 locations before testing. [Elektroda, korsarz50, post #20525244]
Which OBD pins are power and ground on this car?
Pin 16 provides positive supply to the diagnostic port. Pins 4 and 5 are grounds. Use them for voltage checks and powering scan tools. [Elektroda, romuald-f, post #17721155]
What wire color feeds OBD power in some C4 Grand Picasso cars?
One owner traced a blue wire marked 4059 to the 5 A fuse feeding OBD on the battery strip. Wire codes can vary by year and trim. [Elektroda, Mlerte, post #17230644]
All fuses test OK. What’s next?
Verify that power exits the BSI on the green plug’s pin 2. If not, suspect the connector or the BSI unit itself. Repair or replace as required. [Elektroda, Maliniaktg, post #20535379]
After replacing the 5 A fuse, will diagnostics work again?
Yes. Restoring the 5 A battery-strip fuse brought back OBD socket power and computer connectivity in the reported fix. [Elektroda, Mlerte, post #17230644]
