Applicable Systems
OBD-II
Symptoms
Alternator/generator control circuit fault; ECM cannot regulate alternator output; charging system may over/undercharge.
Possible Causes
- Alternator field control circuit open/short
- ECM alternator driver fault
- Alternator internal regulator failure
Troubleshooting Steps
- Step 1: Check alternator field control circuit at ECM
Signal present - Step 2: Check alternator output voltage (13.8-14.4V)
Voltage within range - Step 3: Inspect alternator field wiring
Wiring intact - Step 4: Replace alternator if internal regulator faulty
Voltage stable - 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 smart alternator?
ECM-controlled alternator that adjusts output based on vehicle electrical demand. Improves fuel economy by reducing alternator load when not needed. Uses field control circuit.
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Source: SAE J2012 standard DTC list + OBD-II portal
Category: OBD-II
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