B2172

Code

LAND ROVER B — Body

Failure in the inertia switch input - open circuit

Brand: LAND ROVER

Type: B — Body

Views: UK: 17 EN: 111 RU: 16

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Page language: EN

Causes

Faulty or tripped inertia (impact) switch
Open or shorted wiring between switch and control module
Corroded, loose or damaged connector at the switch or module
Blown fuse or poor fuse contact on the fuel/power circuit
Water intrusion or physical damage to the switch
Faulty body control module (rare) or incorrect module software

Symptoms

Engine cranks but will not start (fuel pump may be disabled)
Intermittent or no fuel pump operation
No obvious fuel pressure at rail
Related warning lights or DTCs present (BCM/fuel system)
No power present to fuel pump circuit until switch is reset

What to check

Retrieve freeze frame and related DTCs with a scan tool; record live data while attempting start
Visually inspect inertia switch location, cover and connector for damage or water ingress
Confirm fuse(s) for fuel pump/inertia circuit are intact and properly seated
Check for 12V supply and good ground at the switch connector with ignition ON
Press/reset the inertia switch (if equipped) and see if condition clears / fuel pump runs
Perform continuity test between switch terminal and BCM/input pin with harness disconnected

Signal parameters

Switch closed: near battery voltage (~11–14 V) present at the inertia switch output/input to BCM with ignition ON
Switch open/tripped: open circuit or ~0 V at BCM input (no continuity to battery)
Continuity across a closed inertia switch: low ohms (typically
Open switch: very high resistance or infinite continuity
Intermittent faults: fluctuating voltage on input when harness is moved

Diagnostic algorithm

Use a scan tool to confirm B2172 and note any additional stored codes or freeze frame data.
Visually inspect the inertia switch assembly and connector for corrosion, damage, or evidence it has been triggered; reset the switch if it has a manual reset button.
Check related fuses and relays (fuel pump/inertia circuit) and replace/seat as required.
With ignition ON, measure battery voltage at the switch supply terminal and at the switch output to the BCM (or wiring harness). If supply is present but output is open, suspect the switch.
With the switch removed/accessible, perform a continuity test across the switch while operating/resetting it. Replace switch if no continuity when closed.
If switch tests OK, trace and test continuity of the wiring from the switch to the BCM input pin; repair any open or damaged conductors and repair corroded connectors.
If wiring and switch are good, check the BCM input circuit for proper pull-up/pull-down and for shorts to ground/power. Consult wiring diagram for pin location and expected behavior.
After repairs, clear DTCs and perform a functional test (attempt start, verify fuel pump operation and scan tool input). Monitor for reoccurrence.
If fault persists after switch and wiring checks, consider BCM diagnostics or replacement as a last resort (follow manufacturer procedures).

Likely causes

Inertia switch has been triggered or mechanically failed
Damaged harness or broken conductor to the switch
Connector pins corroded or pushed out at the switch
Fuse for fuel pump/inertia circuit is blown or not seated
Switch mounted in a location exposed to water/dirt causing failure

Fault status

⚠️ Status

B2172 — Inertia switch input circuit open. The control module detected an open circuit or no input from the inertia (impact) switch, which can interrupt fuel pump power or related safety circuits.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours

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B2172 — Failure in the inertia switch input - open circuit