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Home / DTC / C1420 — Overvoltage Detected

C1420 — Overvoltage Detected

Detailed page for trouble code C1420.

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Code

C1420

HYUNDAI C — Chassis

Overvoltage Detected

Brand: HYUNDAI
Type: C — Chassis
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty/overcharging alternator or voltage regulator
  • Poor or intermittent ground or battery connection
  • Battery voltage above specification (overcharged battery)
  • Short to battery positive (wiring harness or connector damage)
  • High-voltage transient from jump-start, boost, or fault
  • Faulty control module (internal voltage regulation failure)

Symptoms

  • DTC C1420 stored and fault indicator(s) illuminated (ABS/ESC, traction, or master warning lamp depending on module)
  • Erratic behavior of systems controlled by the affected module
  • Intermittent loss of function or limp mode in related systems
  • Battery or charging system warning lamp
  • Possible blown fuses or repeated electrical component failures

What to check

  • Retrieve freeze frame and live data with a scan tool; note voltage at time of fault
  • Measure battery voltage with engine OFF and engine RUNNING using a quality voltmeter
  • Inspect battery terminals, cable ends, and ground straps for tightness and corrosion
  • Visually inspect wiring and connectors to the affected module for damage, heat, or pin corrosion
  • Check main fuses and wiring for signs of short to B+
  • Perform alternator output test and regulator function check (voltage, ripple, load test)

Signal parameters

  • Battery resting voltage (engine off): typically ~12.4–12.8 V
  • Charging voltage (engine running, nominal): typically ~13.5–14.8 V
  • Typical manufacturer overvoltage detection threshold: generally above ~15.5–16.5 V (varies by module)
  • Transient spikes: short-duration voltage surges above module rating may register as overvoltage even if steady voltage is normal
  • Observe voltage under load and during engine start/crank for spikes or excessive excursions

Diagnostic algorithm

  1. Connect a scan tool, confirm C1420 and view stored data/Freeze Frame to see voltage at fault time; record related codes.
  2. Visually inspect battery, cables, ground straps and all power/ground connections to the affected module; repair any corrosion/damage.
  3. Measure and record battery voltage with engine OFF and then with engine RUNNING. Normal running voltage should be ~13.5–14.8 V. If above specification, suspect alternator/regulator.
  4. Perform alternator output and regulator checks (voltmeter and/or oscilloscope): check for overcharging, excessive ripple, or intermittent spikes.
  5. Inspect wiring harness and connectors to module for chafing, melted insulation, or evidence of short to battery positive. Repair damaged wiring.
  6. If transient spikes are suspected, monitor voltage with an oscilloscope or high-speed data logger while exercising systems or attempting to reproduce the fault.
  7. Check related fuses/diodes/surge suppressors; replace any blown or damaged components.
  8. If charging system and wiring are good but overvoltage persists or cannot be reproduced, consider module internal failure. Consult manufacturer service info before replacing module; some modules require reprogramming or initialization.
  9. After repairs, clear codes and confirm no recurrence under normal operation. Verify all affected systems function correctly.

Likely causes

  • Alternator diode/regulator failure causing excessive charging voltage
  • Loose, corroded or damaged battery positive/negative terminals
  • Damaged wiring harness or shorted power feed to the module
  • Aftermarket charger/jump starter creating a voltage spike
  • Control module internal hardware failure or degraded surge protection

Fault status

⚠️ Status
Overvoltage detected by control module. Voltage exceeded allowable threshold or transient spike observed. Investigate charging system, battery, wiring, and module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours
371

Browse 371 HYUNDAI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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Code

C1420

MITSUBISHI C — Chassis

IG SW start POS.circuit low

Brand: MITSUBISHI
Type: C — Chassis
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty/overcharging alternator or voltage regulator
  • Poor or intermittent ground or battery connection
  • Battery voltage above specification (overcharged battery)
  • Short to battery positive (wiring harness or connector damage)
  • High-voltage transient from jump-start, boost, or fault
  • Faulty control module (internal voltage regulation failure)

Symptoms

  • DTC C1420 stored and fault indicator(s) illuminated (ABS/ESC, traction, or master warning lamp depending on module)
  • Erratic behavior of systems controlled by the affected module
  • Intermittent loss of function or limp mode in related systems
  • Battery or charging system warning lamp
  • Possible blown fuses or repeated electrical component failures

What to check

  • Retrieve freeze frame and live data with a scan tool; note voltage at time of fault
  • Measure battery voltage with engine OFF and engine RUNNING using a quality voltmeter
  • Inspect battery terminals, cable ends, and ground straps for tightness and corrosion
  • Visually inspect wiring and connectors to the affected module for damage, heat, or pin corrosion
  • Check main fuses and wiring for signs of short to B+
  • Perform alternator output test and regulator function check (voltage, ripple, load test)

Signal parameters

  • Battery resting voltage (engine off): typically ~12.4–12.8 V
  • Charging voltage (engine running, nominal): typically ~13.5–14.8 V
  • Typical manufacturer overvoltage detection threshold: generally above ~15.5–16.5 V (varies by module)
  • Transient spikes: short-duration voltage surges above module rating may register as overvoltage even if steady voltage is normal
  • Observe voltage under load and during engine start/crank for spikes or excessive excursions

Diagnostic algorithm

  1. Connect a scan tool, confirm C1420 and view stored data/Freeze Frame to see voltage at fault time; record related codes.
  2. Visually inspect battery, cables, ground straps and all power/ground connections to the affected module; repair any corrosion/damage.
  3. Measure and record battery voltage with engine OFF and then with engine RUNNING. Normal running voltage should be ~13.5–14.8 V. If above specification, suspect alternator/regulator.
  4. Perform alternator output and regulator checks (voltmeter and/or oscilloscope): check for overcharging, excessive ripple, or intermittent spikes.
  5. Inspect wiring harness and connectors to module for chafing, melted insulation, or evidence of short to battery positive. Repair damaged wiring.
  6. If transient spikes are suspected, monitor voltage with an oscilloscope or high-speed data logger while exercising systems or attempting to reproduce the fault.
  7. Check related fuses/diodes/surge suppressors; replace any blown or damaged components.
  8. If charging system and wiring are good but overvoltage persists or cannot be reproduced, consider module internal failure. Consult manufacturer service info before replacing module; some modules require reprogramming or initialization.
  9. After repairs, clear codes and confirm no recurrence under normal operation. Verify all affected systems function correctly.

Likely causes

  • Alternator diode/regulator failure causing excessive charging voltage
  • Loose, corroded or damaged battery positive/negative terminals
  • Damaged wiring harness or shorted power feed to the module
  • Aftermarket charger/jump starter creating a voltage spike
  • Control module internal hardware failure or degraded surge protection

Fault status

⚠️ Status
Overvoltage detected by control module. Voltage exceeded allowable threshold or transient spike observed. Investigate charging system, battery, wiring, and module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours
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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Code

C1420

Other C — Chassis

Hydraulic Fluid Pressure/ Flow Circuit Short to Vbatt

Brand: Other
Type: C — Chassis
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty/overcharging alternator or voltage regulator
  • Poor or intermittent ground or battery connection
  • Battery voltage above specification (overcharged battery)
  • Short to battery positive (wiring harness or connector damage)
  • High-voltage transient from jump-start, boost, or fault
  • Faulty control module (internal voltage regulation failure)

Symptoms

  • DTC C1420 stored and fault indicator(s) illuminated (ABS/ESC, traction, or master warning lamp depending on module)
  • Erratic behavior of systems controlled by the affected module
  • Intermittent loss of function or limp mode in related systems
  • Battery or charging system warning lamp
  • Possible blown fuses or repeated electrical component failures

What to check

  • Retrieve freeze frame and live data with a scan tool; note voltage at time of fault
  • Measure battery voltage with engine OFF and engine RUNNING using a quality voltmeter
  • Inspect battery terminals, cable ends, and ground straps for tightness and corrosion
  • Visually inspect wiring and connectors to the affected module for damage, heat, or pin corrosion
  • Check main fuses and wiring for signs of short to B+
  • Perform alternator output test and regulator function check (voltage, ripple, load test)

Signal parameters

  • Battery resting voltage (engine off): typically ~12.4–12.8 V
  • Charging voltage (engine running, nominal): typically ~13.5–14.8 V
  • Typical manufacturer overvoltage detection threshold: generally above ~15.5–16.5 V (varies by module)
  • Transient spikes: short-duration voltage surges above module rating may register as overvoltage even if steady voltage is normal
  • Observe voltage under load and during engine start/crank for spikes or excessive excursions

Diagnostic algorithm

  1. Connect a scan tool, confirm C1420 and view stored data/Freeze Frame to see voltage at fault time; record related codes.
  2. Visually inspect battery, cables, ground straps and all power/ground connections to the affected module; repair any corrosion/damage.
  3. Measure and record battery voltage with engine OFF and then with engine RUNNING. Normal running voltage should be ~13.5–14.8 V. If above specification, suspect alternator/regulator.
  4. Perform alternator output and regulator checks (voltmeter and/or oscilloscope): check for overcharging, excessive ripple, or intermittent spikes.
  5. Inspect wiring harness and connectors to module for chafing, melted insulation, or evidence of short to battery positive. Repair damaged wiring.
  6. If transient spikes are suspected, monitor voltage with an oscilloscope or high-speed data logger while exercising systems or attempting to reproduce the fault.
  7. Check related fuses/diodes/surge suppressors; replace any blown or damaged components.
  8. If charging system and wiring are good but overvoltage persists or cannot be reproduced, consider module internal failure. Consult manufacturer service info before replacing module; some modules require reprogramming or initialization.
  9. After repairs, clear codes and confirm no recurrence under normal operation. Verify all affected systems function correctly.

Likely causes

  • Alternator diode/regulator failure causing excessive charging voltage
  • Loose, corroded or damaged battery positive/negative terminals
  • Damaged wiring harness or shorted power feed to the module
  • Aftermarket charger/jump starter creating a voltage spike
  • Control module internal hardware failure or degraded surge protection

Fault status

⚠️ Status
Overvoltage detected by control module. Voltage exceeded allowable threshold or transient spike observed. Investigate charging system, battery, wiring, and module.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours
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