Dual Alternator Lower Circuit Malfunction (Control)
The P1107 code indicates a malfunction in the lower control circuit of a dual alternator system. This typically occurs in vehicles equipped with two alternators, such as some heavy-duty trucks or high-output vehicles. The lower alternator's control circuit is responsible for regulating its output, and a fault can lead to charging system imbalances, battery drain, or electrical system instability. The issue may stem from wiring problems, a faulty alternator, or a defective control module.
1. Symptoms You Will Notice
- Battery warning light illuminated
- Dimming or flickering headlights
- Dead battery or difficulty starting
- Electrical system voltage fluctuations
2. Most Common Causes
- Damaged or corroded wiring/connectors in the lower alternator control circuit
- Faulty lower alternator
- Defective engine control module (ECM) or alternator control module
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Visually inspect the lower alternator wiring and connectors for damage or corrosion.
Step 3: Test the lower alternator output voltage and compare to specifications.
Step 4: Check the control circuit continuity and resistance between the alternator and ECM.
Step 5: If wiring is intact, test the alternator control module or ECM for proper operation.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause battery drain, electrical system failure, or leave you stranded. Have it diagnosed promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and minor repairs like wiring fixes, but alternator replacement can cost $200-$500 or more.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.