P1108
HondaHonda-specific code indicating a malfunction in the Dual Alternator Battery Lamp Circuit, which is responsible for illuminating the battery warning light on the dashboard.
High SeverityThe P1108 code signifies that your Honda's Powertrain Control Module (PCM) has detected an issue within the Dual Alternator Battery Lamp Circuit. This malfunction can prevent the battery warning light from operating correctly and may indicate a problem with one or both alternators, potentially leading to a failing charging system.
⚠️ Before You Begin (Safety First)
Always disconnect the battery's negative terminal before performing any electrical repairs to prevent accidental shock or damage to the vehicle's electrical components. Ensure the engine is off and cooled down before working near hot parts. Exercise caution when working around rotating engine components.
Common Symptoms
- Battery warning light illuminated on the dashboard
- Dimming headlights or interior lights
- Malfunctioning electrical accessories (radio, power windows)
- Slow engine cranking or no-start condition
- Vehicle stalling while driving
- Unexpected battery drain
Common Causes
- Faulty primary or secondary alternator
- Damaged, chafed, or corroded wiring in the dual alternator battery lamp circuit
- Blown fuse(s) related to the charging system
- Loose or corroded battery terminals or ground connections
- Malfunctioning battery temperature sensor (if applicable)
- Internal PCM fault (rare)
Frequently reported on: Honda Pilot (2006-2008), Honda Odyssey (2005-2007), Honda Ridgeline (2006-2008), Honda Accord V6 (2003-2007)
Diagnostic Steps
- Visually inspect the wiring harnesses leading to both alternators and the battery for any signs of damage, fraying, or corrosion. Ensure all connections are tight.
- Check the battery terminals for corrosion and clean them if necessary. Ensure the battery itself is in good condition and fully charged.
- Locate and inspect all fuses related to the charging system in both the under-hood and cabin fuse boxes. Replace any blown fuses.
- Perform a battery voltage test with the engine off; it should read around 12.6 volts. Start the engine and test the charging voltage; it should typically be between 13.5 and 14.5 volts.
- If possible, test the output of each alternator individually using a multimeter or a specialized alternator tester to confirm proper function.
- If an alternator is found to be faulty, safely remove and replace it, ensuring all connections are properly re-secured.
- After any repairs, clear the P1108 code using an OBD-II scanner and retest the system to ensure the fault does not return.
👨🔧 When to Call a Professional
If you are not equipped with a multimeter or lack experience in advanced electrical circuit diagnosis, including testing individual alternator outputs and wiring for continuity and resistance, it is highly recommended to consult a professional mechanic. Driving with a compromised charging system can lead to a complete vehicle breakdown.
Commonly Asked Questions
Can I continue to drive my Honda with a P1108 code?
It is not recommended to drive with a P1108 code for an extended period. This code indicates a problem with your charging system, and continuing to drive could lead to a dead battery and leave you stranded.
What does 'dual alternator' mean for my Honda?
Some Honda vehicles, especially those with higher electrical demands like SUVs or minivans, are equipped with two alternators to ensure adequate power supply for all vehicle systems. A P1108 code points to an issue with the warning light circuit for this dual system.
Is the P1108 code always caused by a bad alternator?
While a faulty alternator is a common cause, the P1108 code specifically points to a malfunction in the battery lamp circuit. This means the issue could also be with the wiring, a fuse, or even the PCM itself, not just the alternators.
How can I identify which of the dual alternators is faulty?
Diagnosing which alternator is at fault typically requires professional testing. A mechanic will use specialized equipment to test the output of each alternator individually and inspect the associated wiring and control circuits to pinpoint the exact source of the problem.
Will replacing my battery fix the P1108 code?
Only if a failing battery is causing an incorrect voltage reading or overloading the charging system, which in turn triggers the battery lamp circuit malfunction. However, it's more likely that the root cause is with an alternator or the wiring itself rather than just the battery.