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Home / DTC / P0942 — Hydraulic pressure unit

P0942 — Hydraulic pressure unit

Detailed page for trouble code P0942.

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Code

P0942

LAND ROVER P — Powertrain

Hydraulic pressure unit

Brand: LAND ROVER
Type: P — Powertrain
Views: UK: 5 EN: 15 RU: 14
AI status
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Page language: EN

Causes

  • Low or contaminated transmission/hydraulic fluid
  • Faulty hydraulic pressure sensor (pressure transducer)
  • Faulty hydraulic pressure unit / pump / control valve assembly
  • Wiring damage: open, short to ground, short to battery, or poor connection at sensor/HPU
  • Corroded or loose electrical connector(s) at sensor or transmission control unit (TCU)/PCM
  • Faulty transmission control module/TCU or software/calibration error

Symptoms

  • Check Engine/Transmission warning lamp illuminated
  • Harsh, delayed, or erratic shifting
  • Transmission stuck in limp/limitation mode (reduced gear range)
  • Unusual whining or abnormal noise from transmission area (weak pump)
  • Fluid leaks under vehicle or around transmission/HPU area
  • Incorrect line/rail pressure readings in live data

What to check

  • Check for stored transmission/TCU freeze frame data and additional related codes with a capable scan tool
  • Visually inspect transmission fluid level and condition (burnt smell, debris, contamination)
  • Inspect wiring harness and connectors to hydraulic pressure sensor and hydraulic pressure unit for damage, corrosion or loose pins
  • Use scan tool to monitor hydraulic pressure sensor/rail pressure live data during cranking and road test and compare to expected behaviour
  • Check for external fluid leaks around hydraulic pump, valve body, and hoses
  • Perform a basic battery/charging system check (low voltage can cause sensor/actuator faults)

Signal parameters

  • Hydraulic pressure sensor: typical voltage range 0–5 V (sensor output varies with pressure)
  • Solenoid control signals: PWM duty cycle 0–100% from TCU/PCM
  • Hydraulic pump current draw: typically low amps at idle; significant increase under load (manufacturer-specific)
  • Expected line/rail pressure (dependant on transmission): monitor relative changes and correlation with sensor voltage rather than relying on one absolute number without OEM spec

Diagnostic algorithm

  1. Connect OEM-level scan tool and read all transmission/engine/TCU stored and pending codes; record freeze frame data
  2. Verify battery voltage and power/ground to transmission control module and hydraulic pressure sensor with engine off and running
  3. Inspect connectors and wiring between TCU and hydraulic pressure sensor/HPU; repair any damaged pins, corrosion, or chafing
  4. With scan tool, monitor hydraulic pressure sensor output while performing key-on, engine idle and during road test; note any intermittent or implausible values
  5. If sensor output is out of range, backprobe sensor connector and verify sensor reference voltage (usually ~5 V), ground, and sensor signal; repair wiring as required
  6. If wiring and connector are good but signal remains incorrect, test or replace the hydraulic pressure sensor/transducer
  7. If sensor tests OK, perform hydraulic pressure/flow checks per manufacturer procedure (pressure gauge or OEM test harness) to confirm pump/valve body/HPU operation
  8. If mechanical pressure is low or unstable, inspect pressure unit (pump/valve body/solenoid pack) for internal leaks or failure; repair or replace hydraulic pressure unit as required
  9. After repairs, clear codes and perform a road test and full adaptation/learning procedure if required by manufacturer; re-scan to confirm code does not return

Likely causes

  • Low fluid level or very dirty fluid
  • Damaged/loose connector or wiring to hydraulic pressure sensor
  • Failed pressure sensor or pressure control valve pack (hydraulic pressure unit)
  • Internal failure in hydraulic pump or valve body causing insufficient pressure

Fault status

⚠️ Status
Hydraulic pressure unit fault detected — the transmission control module has logged a pressure/circuit fault. Driveability and shifting may be affected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1-4 hours

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