B173d Peugeot Info

The wiring harness that connects the glow plug control unit to the four glow plugs sits directly on top of a hot diesel engine. Over time (60,000+ miles), the insulation becomes brittle. The wire leading to Cylinder 4 often rubs against the engine cover or a fuel line, snapping internally. You may see no external damage, but a continuity test will reveal the break.

You do not need a mechanic for the diagnostic phase. A basic digital multimeter ($20) and an OBD2 scanner are enough.

Step 1: Clear the code and retest. Erase the B173D code, start the engine on a cold morning, and re-scan. If it returns immediately, the fault is permanent.

Step 2: Visual inspection. Open the hood. Locate the glow plug for Cylinder 4. Look for:

Step 3: The Resistance Test (Disconnect the harness). Unplug the electrical connector from the glow plug control unit and test each glow plug directly at the unit's connector pins. You need the pinout diagram for your specific Peugeot engine (DV6 or DW10). For cylinder 4, you should see approximately 0.6 to 1.2 Ohms. b173d peugeot

Step 4: The Harness Test. If the glow plug tests fine (0.6 Ohms), you need to test the wire from the control unit to the plug. Disconnect both ends and use your multimeter on continuity mode. A beep means the wire is good. No beep means the wire is broken.

Step 5: Swap test. If possible, swap the Cylinder 4 glow plug with Cylinder 1. Clear the codes and restart.

Peugeot BlueHDi engines are notorious for carbon buildup. Because the glow plugs extend into the combustion chamber, they become crusted with hard, black carbon. This carbon can:

Depending on the diagnosis, the solution will usually be one of the following: The wiring harness that connects the glow plug

While this code can appear in any modern Peugeot, it is most frequently reported in:

These models share similar door construction and mirror designs that are prone to wiring fatigue near the hinge point.

The sensor receives a 12V or 5V reference from the BSI. A blown fuse in the engine bay fuse box (often F11 or F18, check your manual) can cause this code. Additionally, a BSI that needs a software reset can report false codes.

To understand this fault, you must first forget everything you know about old diesel engines. Step 3: The Resistance Test (Disconnect the harness)

The Old Way: In older diesels, glow plugs only activated for 10–30 seconds before starting the engine to heat the combustion chamber. Once the engine was running, the glow plugs turned off.

The New Way (BlueHDi): Modern Peugeot engines (DV6 and DW10 BlueHDi) use a "Glow Plug Control Unit" that keeps the glow plugs active for up to 3 to 4 minutes after the engine starts. They assist with:

The B173D code specifically points to an electrical open circuit or a resistance issue on the 4th cylinder (the cylinder closest to the timing belt or flywheel, depending on engine orientation). "Open circuit" means the engine control unit (ECU) tried to send voltage to that glow plug, but the electrical loop was broken.