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Home / DTC / B2804 — Reservoir solenoid signal - short circuit to battery

B2804 — Reservoir solenoid signal - short circuit to battery

Detailed page for trouble code B2804.

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Code

B2804

LAND ROVER B — Body

Reservoir solenoid signal - short circuit to battery

Brand: LAND ROVER
Type: B — Body
Views: UK: 8 EN: 11 RU: 12
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Page language: EN

Causes

  • Damaged or chafed wiring contacting battery positive or another switched 12V source
  • Corroded or bridged connector terminals (water ingress, salt corrosion)
  • Failed solenoid with internal short to battery
  • Improper repairs or aftermarket wiring tied into the signal circuit
  • Faulty body/control module (rare) driving incorrect voltage onto the circuit

Symptoms

  • Stored B2804 fault and corresponding warning lamp/message
  • Reservoir solenoid does not operate or operates continuously
  • Related system malfunction (e.g., air suspension reservoir not controlled, depending on vehicle)
  • Possible audible clicking or inability to energize circuit
  • Intermittent faults that may clear with vibration or reconnecting harness

What to check

  • Read live data and fault freeze frame with a diagnostic scanner; confirm B2804 is current or historic
  • Visual inspection of harness and connectors at the reservoir solenoid for damage, corrosion or water
  • Check for +12V present at the solenoid signal terminal with ignition off and with key on (uncommanded voltage indicates short to battery)
  • Measure coil resistance of the solenoid against manufacturer spec
  • Perform continuity checks between the signal pin and battery positive and between signal pin and control module
  • Inspect nearby harnesses and components for aftermarket connections or recent repairs

Signal parameters

  • Battery voltage: ~12–14 V (system battery voltage range)
  • Expected signal: when OFF the solenoid signal line should be near 0 V or open; when ON the control module should apply ~12 V
  • Solenoid coil resistance: compare measured ohms to manufacturer specification (typical coils often tens of ohms)
  • Voltage at harness pin with connector disconnected: unexpected battery voltage indicates short to B+ on vehicle side

Diagnostic algorithm

  1. Use a scanner to confirm DTC B2804 and note freeze-frame/conditions. Attempt to reproduce the fault.
  2. Visually inspect the reservoir solenoid, connector, and harness routing for damage, corrosion, or pinched wiring.
  3. With ignition OFF, disconnect the solenoid connector. Using a DVOM, measure resistance/continuity from the harness signal pin to battery positive. Continuity indicates a short to B+ in the harness or downstream.
  4. With connector disconnected, turn ignition ON (engine off). Measure voltage at the harness signal pin. If ~12 V is present without command, there is a short/incorrect feed on the vehicle side.
  5. Check resistance of the solenoid coil (at the solenoid connector). An internal short will show abnormally low resistance or direct feed. Compare to spec or known-good unit.
  6. Backprobe the control module signal pin while commanding the solenoid ON/OFF with a scanner. Verify the module drives the line correctly (switches to battery when commanded ON, low/open when OFF).
  7. If wiring short suspected, trace and isolate sections of the harness; repair or replace damaged wires and connectors. If the solenoid is faulty, replace it and retest.
  8. After repair, clear codes and perform functional test / road test to confirm fault does not return.
  9. Safety: isolate battery negative before performing extensive wiring repairs to avoid shorts or airbag/ECM issues.

Likely causes

  • Wiring harness damage near reservoir or along harness routing (pinch, rubbing)
  • Connector shorted to adjacent +12V circuit or fused feed
  • Solenoid assembly failed internally and is feeding battery to the signal line
  • Poor ground or connector sealing allowing corrosion and bridging

Fault status

⚠️ Status
Reservoir solenoid signal circuit short to battery detected. Control module senses continuous battery voltage on the solenoid signal line when it should be low or switched by the module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.5 hours

Similar codes

B2800 B2801 B2802 B2803 B2805
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