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Home / DTC / B1794 — Active headlight switch with inactive sidelight switch

B1794 — Active headlight switch with inactive sidelight switch

Detailed page for trouble code B1794.

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Code

B1794

LAND ROVER B — Body

Active headlight switch with inactive sidelight switch

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

Causes

  • Faulty headlight or sidelight switch (stalk/rotary)
  • Damaged wiring harness or broken/shorted connector pins between switch and body control module (BCM)
  • Corroded or loose connectors at switch or BCM
  • Faulty body control module / lighting control module
  • Blown fuse or faulty relay affecting sidelight circuit
  • CAN bus or module communication error

Symptoms

  • DTC B1794 stored in memory and may trigger a dashboard warning
  • Sidelights (parking lights) do not come on when expected or behave inconsistently
  • Headlights operate while sidelight indicator does not follow expected state
  • Erratic or intermittent lighting operation
  • Possible loss of other exterior lighting functions tied to BCM

What to check

  • Read and record all stored DTCs and freeze frame data with a capable diagnostic tool
  • Check for any related communication codes (U-codes) that indicate CAN/communication faults
  • Visually inspect headlight switch, stalk and connectors for damage, corrosion, moisture or foreign debris
  • Inspect BCM connector and body harness for corrosion, bent pins, water ingress or impact damage
  • Verify fuses and relays for the lighting circuits (replace if suspect)
  • Operate headlight and sidelight switches while watching live data stream for switch status bits from the switch and the BCM response

Signal parameters

  • Switch input voltage: ~0 V (OFF) or ~9–12 V (ON) depending on vehicle wiring
  • Ground continuity: near 0 Ω between switch ground and chassis ground
  • CAN bus voltage: nominal ~2.5 V on CAN_H/CAN_L differential idle (verify with CAN tool)
  • Resistance/continuity values for switch terminals: low resistance when closed, open when open (compare to known-good values)
  • Diagnostic tool live data: headlight switch state (binary), sidelight switch state (binary)

Diagnostic algorithm

  1. Connect a factory-level or equivalent diagnostic scanner. Read and record all DTCs and live data. Note when B1794 sets and any accompanying codes.
  2. Clear codes and attempt to reproduce the fault by operating headlight and sidelight controls while monitoring live data for both switch inputs and BCM status bits.
  3. Visually inspect switch, connectors and associated harness for damage, corrosion, moisture. Repair any obvious wiring damage.
  4. Check fuses and relays for lighting circuits. Replace if suspect and re-test.
  5. With ignition on, use a multimeter to probe the switch harness: confirm voltage changes at the switch when toggling headlight and sidelight positions; verify continuity to the BCM input pin.
  6. Backprobe the BCM input with diagnostic tool active to confirm the BCM receives the correct switch status. If switch registers correctly at the switch harness but not at the BCM, suspect wiring or connector between them.
  7. Wiggle-test connectors and harness while watching live data to find intermittent faults. Repair or replace damaged connectors/harness sections.
  8. If wiring and switch are good but the BCM does not register inputs correctly, check for CAN-bus related codes and test communication with other modules. Reprogram or update BCM software if a calibration/flash is available.
  9. If module input circuit is confirmed faulty and wiring/switch are good, replace or repair the BCM per manufacturer procedures. After any repair, clear codes and verify repair by retesting switch operations and ensuring no reoccurrence.
  10. Document repair and consider immobilizer/cluster alignment procedures if BCM replaced per manufacturer service instructions.

Likely causes

  • Defective headlight/sidelight switch
  • Open/short in switch-to-BCM wiring or poor ground
  • Intermittent connector contact or corrosion at the BCM connector
  • Module input channel fault or BCM software glitch

Fault status

⚠️ Status
Headlight switch active while sidelight switch inactive — input mismatch reported to body control module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.5 hours

Similar codes

B1793 B1795 B1796 U0100 U0155
320

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

LAND ROVER

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Code

B1794

Other B — Body

Lamp Headlamp Low-Beam Circuit Failure

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

Causes

  • Faulty headlight or sidelight switch (stalk/rotary)
  • Damaged wiring harness or broken/shorted connector pins between switch and body control module (BCM)
  • Corroded or loose connectors at switch or BCM
  • Faulty body control module / lighting control module
  • Blown fuse or faulty relay affecting sidelight circuit
  • CAN bus or module communication error

Symptoms

  • DTC B1794 stored in memory and may trigger a dashboard warning
  • Sidelights (parking lights) do not come on when expected or behave inconsistently
  • Headlights operate while sidelight indicator does not follow expected state
  • Erratic or intermittent lighting operation
  • Possible loss of other exterior lighting functions tied to BCM

What to check

  • Read and record all stored DTCs and freeze frame data with a capable diagnostic tool
  • Check for any related communication codes (U-codes) that indicate CAN/communication faults
  • Visually inspect headlight switch, stalk and connectors for damage, corrosion, moisture or foreign debris
  • Inspect BCM connector and body harness for corrosion, bent pins, water ingress or impact damage
  • Verify fuses and relays for the lighting circuits (replace if suspect)
  • Operate headlight and sidelight switches while watching live data stream for switch status bits from the switch and the BCM response

Signal parameters

  • Switch input voltage: ~0 V (OFF) or ~9–12 V (ON) depending on vehicle wiring
  • Ground continuity: near 0 Ω between switch ground and chassis ground
  • CAN bus voltage: nominal ~2.5 V on CAN_H/CAN_L differential idle (verify with CAN tool)
  • Resistance/continuity values for switch terminals: low resistance when closed, open when open (compare to known-good values)
  • Diagnostic tool live data: headlight switch state (binary), sidelight switch state (binary)

Diagnostic algorithm

  1. Connect a factory-level or equivalent diagnostic scanner. Read and record all DTCs and live data. Note when B1794 sets and any accompanying codes.
  2. Clear codes and attempt to reproduce the fault by operating headlight and sidelight controls while monitoring live data for both switch inputs and BCM status bits.
  3. Visually inspect switch, connectors and associated harness for damage, corrosion, moisture. Repair any obvious wiring damage.
  4. Check fuses and relays for lighting circuits. Replace if suspect and re-test.
  5. With ignition on, use a multimeter to probe the switch harness: confirm voltage changes at the switch when toggling headlight and sidelight positions; verify continuity to the BCM input pin.
  6. Backprobe the BCM input with diagnostic tool active to confirm the BCM receives the correct switch status. If switch registers correctly at the switch harness but not at the BCM, suspect wiring or connector between them.
  7. Wiggle-test connectors and harness while watching live data to find intermittent faults. Repair or replace damaged connectors/harness sections.
  8. If wiring and switch are good but the BCM does not register inputs correctly, check for CAN-bus related codes and test communication with other modules. Reprogram or update BCM software if a calibration/flash is available.
  9. If module input circuit is confirmed faulty and wiring/switch are good, replace or repair the BCM per manufacturer procedures. After any repair, clear codes and verify repair by retesting switch operations and ensuring no reoccurrence.
  10. Document repair and consider immobilizer/cluster alignment procedures if BCM replaced per manufacturer service instructions.

Likely causes

  • Defective headlight/sidelight switch
  • Open/short in switch-to-BCM wiring or poor ground
  • Intermittent connector contact or corrosion at the BCM connector
  • Module input channel fault or BCM software glitch

Fault status

⚠️ Status
Headlight switch active while sidelight switch inactive — input mismatch reported to body control module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.5 hours

Similar codes

B1793 B1795 B1796 U0100 U0155
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