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DTC Codes / Powertrain

P0620 — Generator (Alternator) Control Circuit

Powertrainmedium

The engine computer has a problem with the wire it uses to control the alternator.

Symptoms

  • Battery light on
  • Low or no charging

Common causes

  • Damaged alternator plug or wire
  • Faulty alternator
  • ECM fault (rare)

How to fix

  1. Check the alternator plug
  2. Check charging voltage 13.5–14.7 V
  3. Test the control wire to the ECM

Can I keep driving?

Short trips only — the battery may run flat.

Related diagrams

Battery12 VAlternatorVoltageregulatorrotor + stator(makes the power)Main fuseBIgnitionIG fuseIGSS = senses battery voltageBattery light (meter)L1234
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Alternator Charging Circuit (B, IG, S, L) — Battery Light Explained

How the alternator charges the battery, what terminals B, IG, S and L do, and how to test charging.

These are the general meanings. Some companies use a code a little differently — confirm with a scanner and your car's service manual.