Applicable Systems
OBD-II
Symptoms
Alternator field terminal signal low; ECM detects field circuit short to ground; alternator may not charge.
Possible Causes
- Field wire short to ground
- Alternator internal field winding short
- ECM field driver failure
Troubleshooting Steps
- Step 1: Check field terminal at alternator for short to ground
No short - Step 2: Measure field winding resistance
Resistance within spec - Step 3: Inspect field wiring for chafing
Wiring intact - Step 4: Replace alternator if field shorted
New alternator charges normally - Step 5: Clear code and verify charging
Charging system normal
How to Reset
Clear with OBD-II scanner after repair.
Common Replacement Parts
- Alternator (OEM spec)
Frequently Asked Questions
- Q: What is alternator field circuit?
Field winding creates magnetic field for alternator. ECM controls field current to regulate output voltage. F terminal = field monitor signal.
Source: SAE J2012 standard DTC list + OBD-II portal
Category: OBD-II