Dual Alternator Battery Lamp Circuit Malfunction
Your vehicle's dual alternator warning light circuit isn't working properly, similar to a brake light that won't turn on when you need it. The ECU can't confirm the charging system is functioning through the secondary alert circuit.
The ECU monitors the dual alternator battery lamp circuit voltage to verify the charging system alert pathway is functional. It sends a signal to illuminate the lamp during key-on self-test and expects proper voltage feedback. If the circuit voltage remains out of range or unresponsive, the fault code triggers.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Lamp Circuit Voltage | 12V during key-on test, 0V during engine run | Stays above 1V or below expected threshold during operation |
| Signal Response Time | Lamp illuminates within 500ms of command | No response or delayed response >1 second |
Code P1113 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1113 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.