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Home / DTC / B1501 — Left turn indicator warning lamp short to positive

B1501 — Left turn indicator warning lamp short to positive

Detailed page for trouble code B1501.

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Code

B1501

ALFA ROMEO B — Body

Left turn indicator warning lamp short to positive

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

Causes

  • Wiring short to battery positive on the left turn indicator lamp circuit
  • Corroded/damaged lamp socket or connector bridging to +12V
  • Faulty turn signal switch or multifunction stalk
  • Instrument cluster or BCM internal fault (lamp driver shorted)
  • Aftermarket accessory or repair that bridged the circuit
  • Incorrect bulb type or bulb contact causing unintended positive feed

Symptoms

  • Left turn indicator warning lamp illuminated continuously on dash
  • Left turn lamps may not flash correctly or may be stuck on
  • Possible blown fuse or repeated fuse failures for lighting circuit
  • Possible battery drain if short is permanent
  • Related multifunction switch functions intermittent or non-functional

What to check

  • Read and record freeze-frame/live data and confirm B1501 is stored and current
  • Visually inspect left turn lamp(s), sockets, outer lenses and wiring for damage or corrosion
  • Check relevant fuses and fuse box for signs of overheating or corrosion
  • Measure voltage at the left turn lamp connector with ignition OFF and ON (expect ~0V with OFF and ~pulsed 12V when signalling)
  • Unplug left lamp connector and check for +12V presence to determine if circuit is backfeeding
  • Inspect and wiggle-test connectors, harness routing, and multifunction switch while monitoring the circuit

Signal parameters

  • Ignition OFF: lamp circuit should read ~0 V (no battery positive present)
  • Ignition ON, turn signal OFF: lamp circuit should read ~0 V (no continuous feed)
  • When left turn is activated: pulsed ~12 V (duty cycle depends on flasher/BCM, typically ~50% at ~1–2 Hz)
  • Short to positive condition: steady ~12 V present on circuit when it should be 0 V
  • Resistance to ground for lamp circuit with connector disconnected should be high (open circuit except lamp load)

Diagnostic algorithm

  1. Confirm the code with a diagnostic scanner and note any related codes (left/right indicator, BCM, cluster).
  2. Reproduce the symptom: observe dash indicator and external lamps while scanning live data.
  3. Visually inspect left-side lamps, sockets, connectors, and nearby wiring for chafing, corrosion or water ingress.
  4. With ignition OFF, disconnect the left turn lamp connector. Measure voltage between the lamp + terminal and ground. If ~12 V is present with connector disconnected, the short is upstream (toward BCM/switch).
  5. If no voltage with lamp disconnected, reconnect lamp and unplug the BCM/cluster connector for the circuit (if accessible). Check for voltage at BCM output pin to determine if the module is driving or the short is external.
  6. Check continuity between the lamp positive pin and battery positive to locate any unintended direct connection. Use a multimeter or low-current test light; if needed, measure current draw in the circuit to detect a short.
  7. Inspect and test the multifunction switch: backprobe switch outputs while operating switch; replace or bench-test if it sends continuous +12 V incorrectly.
  8. If wiring and switch check good, suspect BCM/instrument cluster driver fault. Confirm by substituting known-good module (where possible) or bench-testing module outputs per service manual.
  9. Repair damaged wiring or connectors (replace harness sections, repair sockets), replace faulty switch or module as required. Clear codes and retest for absence of fault and correct operation.
  10. After repair, monitor for intermittent faults and verify no additional related codes appear.

Likely causes

  • Damaged insulation where the left front/rear lamp harness rubs against bodywork, contacting a constant +12V source
  • Corroded lamp socket terminals creating a path to a fused +12V feed
  • Faulty turn signal switch sending continuous +12V to the lamp circuit
  • Failed lamp driver transistor inside the BCM/instrument cluster shorted to B+
  • Recent aftermarket lighting (LED conversions) installed without proper resistors/adapters

Fault status

⚠️ Status
Left turn indicator warning lamp - short to positive
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1500 B1502 B1503 B1510
89

Browse 89 ALFA ROMEO manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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Code

B1501

FIAT B — Body

Left turn indicator warning lamp short to positive

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

Causes

  • Wiring short to battery positive on the left turn indicator lamp circuit
  • Corroded/damaged lamp socket or connector bridging to +12V
  • Faulty turn signal switch or multifunction stalk
  • Instrument cluster or BCM internal fault (lamp driver shorted)
  • Aftermarket accessory or repair that bridged the circuit
  • Incorrect bulb type or bulb contact causing unintended positive feed

Symptoms

  • Left turn indicator warning lamp illuminated continuously on dash
  • Left turn lamps may not flash correctly or may be stuck on
  • Possible blown fuse or repeated fuse failures for lighting circuit
  • Possible battery drain if short is permanent
  • Related multifunction switch functions intermittent or non-functional

What to check

  • Read and record freeze-frame/live data and confirm B1501 is stored and current
  • Visually inspect left turn lamp(s), sockets, outer lenses and wiring for damage or corrosion
  • Check relevant fuses and fuse box for signs of overheating or corrosion
  • Measure voltage at the left turn lamp connector with ignition OFF and ON (expect ~0V with OFF and ~pulsed 12V when signalling)
  • Unplug left lamp connector and check for +12V presence to determine if circuit is backfeeding
  • Inspect and wiggle-test connectors, harness routing, and multifunction switch while monitoring the circuit

Signal parameters

  • Ignition OFF: lamp circuit should read ~0 V (no battery positive present)
  • Ignition ON, turn signal OFF: lamp circuit should read ~0 V (no continuous feed)
  • When left turn is activated: pulsed ~12 V (duty cycle depends on flasher/BCM, typically ~50% at ~1–2 Hz)
  • Short to positive condition: steady ~12 V present on circuit when it should be 0 V
  • Resistance to ground for lamp circuit with connector disconnected should be high (open circuit except lamp load)

Diagnostic algorithm

  1. Confirm the code with a diagnostic scanner and note any related codes (left/right indicator, BCM, cluster).
  2. Reproduce the symptom: observe dash indicator and external lamps while scanning live data.
  3. Visually inspect left-side lamps, sockets, connectors, and nearby wiring for chafing, corrosion or water ingress.
  4. With ignition OFF, disconnect the left turn lamp connector. Measure voltage between the lamp + terminal and ground. If ~12 V is present with connector disconnected, the short is upstream (toward BCM/switch).
  5. If no voltage with lamp disconnected, reconnect lamp and unplug the BCM/cluster connector for the circuit (if accessible). Check for voltage at BCM output pin to determine if the module is driving or the short is external.
  6. Check continuity between the lamp positive pin and battery positive to locate any unintended direct connection. Use a multimeter or low-current test light; if needed, measure current draw in the circuit to detect a short.
  7. Inspect and test the multifunction switch: backprobe switch outputs while operating switch; replace or bench-test if it sends continuous +12 V incorrectly.
  8. If wiring and switch check good, suspect BCM/instrument cluster driver fault. Confirm by substituting known-good module (where possible) or bench-testing module outputs per service manual.
  9. Repair damaged wiring or connectors (replace harness sections, repair sockets), replace faulty switch or module as required. Clear codes and retest for absence of fault and correct operation.
  10. After repair, monitor for intermittent faults and verify no additional related codes appear.

Likely causes

  • Damaged insulation where the left front/rear lamp harness rubs against bodywork, contacting a constant +12V source
  • Corroded lamp socket terminals creating a path to a fused +12V feed
  • Faulty turn signal switch sending continuous +12V to the lamp circuit
  • Failed lamp driver transistor inside the BCM/instrument cluster shorted to B+
  • Recent aftermarket lighting (LED conversions) installed without proper resistors/adapters

Fault status

⚠️ Status
Left turn indicator warning lamp - short to positive
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1500 B1502 B1503 B1510
Repair manuals

Manual library for FIAT

26

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FIAT

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Code

B1501

MITSUBISHI B — Body

RR curtain ABG squib open

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

Causes

  • Wiring short to battery positive on the left turn indicator lamp circuit
  • Corroded/damaged lamp socket or connector bridging to +12V
  • Faulty turn signal switch or multifunction stalk
  • Instrument cluster or BCM internal fault (lamp driver shorted)
  • Aftermarket accessory or repair that bridged the circuit
  • Incorrect bulb type or bulb contact causing unintended positive feed

Symptoms

  • Left turn indicator warning lamp illuminated continuously on dash
  • Left turn lamps may not flash correctly or may be stuck on
  • Possible blown fuse or repeated fuse failures for lighting circuit
  • Possible battery drain if short is permanent
  • Related multifunction switch functions intermittent or non-functional

What to check

  • Read and record freeze-frame/live data and confirm B1501 is stored and current
  • Visually inspect left turn lamp(s), sockets, outer lenses and wiring for damage or corrosion
  • Check relevant fuses and fuse box for signs of overheating or corrosion
  • Measure voltage at the left turn lamp connector with ignition OFF and ON (expect ~0V with OFF and ~pulsed 12V when signalling)
  • Unplug left lamp connector and check for +12V presence to determine if circuit is backfeeding
  • Inspect and wiggle-test connectors, harness routing, and multifunction switch while monitoring the circuit

Signal parameters

  • Ignition OFF: lamp circuit should read ~0 V (no battery positive present)
  • Ignition ON, turn signal OFF: lamp circuit should read ~0 V (no continuous feed)
  • When left turn is activated: pulsed ~12 V (duty cycle depends on flasher/BCM, typically ~50% at ~1–2 Hz)
  • Short to positive condition: steady ~12 V present on circuit when it should be 0 V
  • Resistance to ground for lamp circuit with connector disconnected should be high (open circuit except lamp load)

Diagnostic algorithm

  1. Confirm the code with a diagnostic scanner and note any related codes (left/right indicator, BCM, cluster).
  2. Reproduce the symptom: observe dash indicator and external lamps while scanning live data.
  3. Visually inspect left-side lamps, sockets, connectors, and nearby wiring for chafing, corrosion or water ingress.
  4. With ignition OFF, disconnect the left turn lamp connector. Measure voltage between the lamp + terminal and ground. If ~12 V is present with connector disconnected, the short is upstream (toward BCM/switch).
  5. If no voltage with lamp disconnected, reconnect lamp and unplug the BCM/cluster connector for the circuit (if accessible). Check for voltage at BCM output pin to determine if the module is driving or the short is external.
  6. Check continuity between the lamp positive pin and battery positive to locate any unintended direct connection. Use a multimeter or low-current test light; if needed, measure current draw in the circuit to detect a short.
  7. Inspect and test the multifunction switch: backprobe switch outputs while operating switch; replace or bench-test if it sends continuous +12 V incorrectly.
  8. If wiring and switch check good, suspect BCM/instrument cluster driver fault. Confirm by substituting known-good module (where possible) or bench-testing module outputs per service manual.
  9. Repair damaged wiring or connectors (replace harness sections, repair sockets), replace faulty switch or module as required. Clear codes and retest for absence of fault and correct operation.
  10. After repair, monitor for intermittent faults and verify no additional related codes appear.

Likely causes

  • Damaged insulation where the left front/rear lamp harness rubs against bodywork, contacting a constant +12V source
  • Corroded lamp socket terminals creating a path to a fused +12V feed
  • Faulty turn signal switch sending continuous +12V to the lamp circuit
  • Failed lamp driver transistor inside the BCM/instrument cluster shorted to B+
  • Recent aftermarket lighting (LED conversions) installed without proper resistors/adapters

Fault status

⚠️ Status
Left turn indicator warning lamp - short to positive
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1500 B1502 B1503 B1510
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MITSUBISHI

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Keep it short and practical. Up to 500 characters.
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Code

B1501

Other B — Body

Lamp Turn Signal Left Circuit Short To Battery

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

Causes

  • Wiring short to battery positive on the left turn indicator lamp circuit
  • Corroded/damaged lamp socket or connector bridging to +12V
  • Faulty turn signal switch or multifunction stalk
  • Instrument cluster or BCM internal fault (lamp driver shorted)
  • Aftermarket accessory or repair that bridged the circuit
  • Incorrect bulb type or bulb contact causing unintended positive feed

Symptoms

  • Left turn indicator warning lamp illuminated continuously on dash
  • Left turn lamps may not flash correctly or may be stuck on
  • Possible blown fuse or repeated fuse failures for lighting circuit
  • Possible battery drain if short is permanent
  • Related multifunction switch functions intermittent or non-functional

What to check

  • Read and record freeze-frame/live data and confirm B1501 is stored and current
  • Visually inspect left turn lamp(s), sockets, outer lenses and wiring for damage or corrosion
  • Check relevant fuses and fuse box for signs of overheating or corrosion
  • Measure voltage at the left turn lamp connector with ignition OFF and ON (expect ~0V with OFF and ~pulsed 12V when signalling)
  • Unplug left lamp connector and check for +12V presence to determine if circuit is backfeeding
  • Inspect and wiggle-test connectors, harness routing, and multifunction switch while monitoring the circuit

Signal parameters

  • Ignition OFF: lamp circuit should read ~0 V (no battery positive present)
  • Ignition ON, turn signal OFF: lamp circuit should read ~0 V (no continuous feed)
  • When left turn is activated: pulsed ~12 V (duty cycle depends on flasher/BCM, typically ~50% at ~1–2 Hz)
  • Short to positive condition: steady ~12 V present on circuit when it should be 0 V
  • Resistance to ground for lamp circuit with connector disconnected should be high (open circuit except lamp load)

Diagnostic algorithm

  1. Confirm the code with a diagnostic scanner and note any related codes (left/right indicator, BCM, cluster).
  2. Reproduce the symptom: observe dash indicator and external lamps while scanning live data.
  3. Visually inspect left-side lamps, sockets, connectors, and nearby wiring for chafing, corrosion or water ingress.
  4. With ignition OFF, disconnect the left turn lamp connector. Measure voltage between the lamp + terminal and ground. If ~12 V is present with connector disconnected, the short is upstream (toward BCM/switch).
  5. If no voltage with lamp disconnected, reconnect lamp and unplug the BCM/cluster connector for the circuit (if accessible). Check for voltage at BCM output pin to determine if the module is driving or the short is external.
  6. Check continuity between the lamp positive pin and battery positive to locate any unintended direct connection. Use a multimeter or low-current test light; if needed, measure current draw in the circuit to detect a short.
  7. Inspect and test the multifunction switch: backprobe switch outputs while operating switch; replace or bench-test if it sends continuous +12 V incorrectly.
  8. If wiring and switch check good, suspect BCM/instrument cluster driver fault. Confirm by substituting known-good module (where possible) or bench-testing module outputs per service manual.
  9. Repair damaged wiring or connectors (replace harness sections, repair sockets), replace faulty switch or module as required. Clear codes and retest for absence of fault and correct operation.
  10. After repair, monitor for intermittent faults and verify no additional related codes appear.

Likely causes

  • Damaged insulation where the left front/rear lamp harness rubs against bodywork, contacting a constant +12V source
  • Corroded lamp socket terminals creating a path to a fused +12V feed
  • Faulty turn signal switch sending continuous +12V to the lamp circuit
  • Failed lamp driver transistor inside the BCM/instrument cluster shorted to B+
  • Recent aftermarket lighting (LED conversions) installed without proper resistors/adapters

Fault status

⚠️ Status
Left turn indicator warning lamp - short to positive
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

B1500 B1502 B1503 B1510
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