Dual Alternator Battery Lamp Circuit Malfunction
The P1108 code indicates a malfunction in the battery lamp circuit of the dual alternator system. This typically occurs when the powertrain control module (PCM) detects an abnormal voltage or current in the circuit that controls the battery warning light. The dual alternator setup is common in heavy-duty or high-output vehicles, and this fault can affect charging system monitoring.
1. Symptoms You Will Notice
- Battery warning light stays on or does not illuminate
- Intermittent charging system issues
- Possible battery drain or overcharging
2. Most Common Causes
- Faulty battery lamp bulb or socket
- Damaged wiring or connector in the lamp circuit
- Defective alternator voltage regulator
- PCM internal fault
3. Step-by-Step Diagnosis
Step 1: Inspect the battery lamp bulb and socket for damage or corrosion.
Step 2: Check wiring and connectors between the alternator and PCM for breaks or shorts.
Step 3: Test alternator output voltage and regulator function.
Step 4: Use a scan tool to monitor PCM commands to the lamp circuit.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short distances, but the charging system may not be monitored properly, risking battery drain or overcharging. Have it diagnosed soon.
How much does it cost to fix?▼
Typical repair costs range from $50 to $150, depending on whether it's a simple bulb replacement or wiring repair.
5. Commonly Affected Makes
This is a manufacturer-specific code. The exact manufacturer is not confirmed in our current database.