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Home / DTC / P1252 — Vacuum switching valve stuck in vacuum to atmosphere / vacuum for vacuum

P1252 — Vacuum switching valve stuck in vacuum to atmosphere / vacuum for vacuum

Detailed page for trouble code P1252.

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P1252

LAND ROVER P — Powertrain

Vacuum switching valve stuck in vacuum to atmosphere / vacuum for vacuum

Brand: LAND ROVER
Type: P — Powertrain
Views: UK: 18 EN: 34 RU: 18
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Page language: EN

Causes

  • Failed or seized vacuum switching valve (stuck open or closed)
  • Blocked, collapsed, disconnected or leaking vacuum hoses
  • Faulty electrical connection to the valve (open/short/corroded connector)
  • Broken wiring, intermittent connection, or poor ground
  • Contaminated valve (carbon, oil or debris preventing movement)
  • Faulty engine control module (rare) or incorrect software/calibration

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Loss or intermittent operation of vacuum‑controlled systems (e.g., actuators, EVAP purge, HVAC doors, brake booster depending on application)
  • Hissing vacuum leak noise near valve/hose
  • Rough idle, hesitation or reduced driveability if vacuum used for engine control
  • Failed emissions test or EVAP/secondary air related faults

What to check

  • Retrieve freeze frame and mode 06/Live data with a scan tool to confirm conditions when code set
  • Visual inspection of VSV, vacuum hoses and fittings for damage, disconnection or contamination
  • Check connector for corrosion, bent pins and secure fit
  • Measure supply voltage at valve connector with ignition on (battery voltage expected)
  • Backprobing control signal from ECU (verify switching or PWM) while commanding valve
  • Perform a manual vacuum/bench test to see if valve holds or vents vacuum as commanded

Signal parameters

  • Supply voltage: battery voltage (~11–14 V) at ignition ON (verify with meter)
  • Control signal: switched ground or PWM from ECU when commanded (scan tool should show command status)
  • Coil resistance: low ohm range (manufacturer spec required) — measure continuity and compare to service data
  • Vacuum response: valve should allow vacuum or vent to atmosphere immediately when commanded (no significant delay)
  • Vacuum hold: when closed, vacuum should be held without rapid decay (use vacuum gauge)

Diagnostic algorithm

  1. Read and record freeze frame, pending codes and related stored codes. Note operating conditions.
  2. Perform a visual inspection of the VSV, vacuum hose routing, clamps and connectors for obvious faults.
  3. With key ON, verify battery voltage at the VSV power pin. If power missing, trace fuse/relay/circuit.
  4. Command the valve ON/OFF with a scan tool while monitoring control wire for expected switching or PWM. If no command, check ECU outputs and wiring.
  5. Backprobe the valve and bench test: apply 12 V/ground as specified to operate solenoid and apply vacuum to confirm it vents and holds as designed. Replace if it fails to operate.
  6. Pressure/vacuum test hoses and associated components (smoke test or vacuum pump) to locate leaks or blockages.
  7. Repair/replace damaged hoses, connectors or the valve as required. Ensure correct part per VIN/manufacturer.
  8. Clear codes and road test under original conditions to confirm repair. Re-scan to verify code does not return.
  9. If electrical faults persist after repairs, inspect/repair wiring harness, test continuity to ECU and consider ECU diagnostics if wiring and component tests are good.

Likely causes

  • VSV mechanical failure (internal stuck piston/diaphragm)
  • Vacuum hose collapsed or disconnected at valve or manifold
  • Connector corrosion or damaged pins at valve
  • Vacuum supply weakness (intake manifold leak or blocked port)
  • Valve contaminated by oil/soot from PCV or turbo system

Fault status

⚠️ Status
Vacuum switching valve stuck between vacuum and atmosphere or stuck supplying vacuum. ECU detected incorrect valve response or abnormal vacuum flow; this may disable or impair vacuum‑operated systems and trigger the MIL.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours

Similar codes

P0440 P0441 P0442 P0491
320

Browse 320 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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