Applicable Systems
OBD-II

Symptoms

Alternator field terminal signal high; ECM detects field circuit short to +V; alternator may overcharge.

Possible Causes

  • Field wire short to +12V
  • Alternator internal field circuit failure
  • ECM field driver shorted high

Troubleshooting Steps

  1. Step 1: Check field terminal for short to +12V
    No short
  2. Step 2: Check field wiring for chafing to +12V
    No chafing
  3. Step 3: Replace alternator if internal fault
    New alternator normal
  4. Step 4: Clear code and verify charging voltage
    Voltage 13.8-14.4V

How to Reset

Clear with OBD-II scanner after repair.

Common Replacement Parts

  • Alternator (OEM spec)

Frequently Asked Questions

  • Q: Can field circuit cause overcharging?

    Yes. If field circuit is shorted to +12V, alternator goes to full field (maximum output), causing overcharging and battery damage.

Related OBD-II Generic (SAE J2012) Fault Codes

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Source: SAE J2012 standard DTC list + OBD-II portal

Category: OBD-II