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Home / DTC / B1157 — Fan control 'B'

B1157 — Fan control 'B'

Detailed page for trouble code B1157.

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Code

B1157

LAND ROVER B — Body

Fan control 'B'

Brand: LAND ROVER
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or shorted wiring in fan control 'B' circuit
  • Poor or corroded connector/ground at blower motor or control module
  • Faulty blower motor (high-current failure) or blower motor module/resistor pack
  • Faulty HVAC control unit or body control module (BCM) output transistor
  • Blown fuse or failed relay supplying the blower circuit
  • Water ingress or debris causing intermittent contact

Symptoms

  • HVAC fan inoperative on one or more speed settings
  • Fan only works at certain speeds or runs at full speed uncontrollably
  • Intermittent blower operation or fan cutting in/out
  • HVAC warning messages or fault lamp illuminated
  • Reduced cabin heating or cooling performance

What to check

  • Read freeze frame and live data with a capable scan tool; note when fault sets (ignition state, fan command, vehicle temperature)
  • Perform visual inspection of blower motor, connector, and wiring harness for damage, corrosion, or water ingress
  • Check relevant fuses and relays for continuity and proper operation
  • Verify ground continuity between blower motor negative and chassis/BCM ground
  • With connector disconnected, check blower motor resistance and for signs of seizure or high current draw
  • Back-probe control and power pins at blower motor/module while commanding fan through scanner; observe voltage and PWM signal

Signal parameters

  • Supply voltage to blower motor: ~12–14 V when commanded ON (key on, engine running)
  • Motor return/ground: near 0 V when properly grounded
  • PWM control signal (if applicable): 0–100% duty cycle; frequency typically tens to a few hundred Hz (manufacturer-specific)
  • Motor current draw: typically a few amps for small blowers; heavy-duty blowers can draw 5–20 A — compare to spec
  • Connector/backprobe voltages should switch in coordination with commanded fan speed

Diagnostic algorithm

  1. Retrieve and record freeze-frame and live data for B1157 and any related codes.
  2. Visually inspect blower motor, resistor/module, connectors, and wiring for corrosion, damage, or water ingress. Repair or secure as needed.
  3. Check fuses and blower relay; replace if faulty. Test relay operation by applying power and verifying contacts close.
  4. With ignition OFF, disconnect blower motor connector and check resistance of motor windings; compare to service spec. Spin motor by hand for roughness.
  5. Reconnect and back-probe power and control circuits. Command fan ON with a scan tool and verify battery voltage at the power feed and proper switching at the control/ground side. Observe PWM duty/frequency if present.
  6. Measure current draw while commanding blower. Excessive current suggests a seized or shorted motor; no current suggests open circuit or relay/fuse issue.
  7. If wiring and motor check good, test or swap blower motor control module / resistor pack (if separate) according to service manual. Inspect and test BCM/HVAC control output if the module is integrated.
  8. If hardware checks pass, consult manufacturer service information for module calibration/software updates and perform flashing or relearn procedures if indicated.
  9. Clear codes and perform operational test cycle to verify fault does not recur.

Likely causes

  • Corroded connector or poor ground at blower motor or fan module
  • Failed blower motor module (PWM driver)
  • Open/short in harness to blower motor (chafing, rodent damage)
  • Blown fuse or failed relay feeding the blower circuit

Fault status

⚠️ Status
Fault detected in HVAC blower/fan control circuit 'B' — electrical or control fault preventing normal fan operation.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1156 B1158 P0480 P0481 B1120
413

Browse 413 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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