P1108
VWDual Alternator Battery Lamp Circuit Malfunction
Medium SeverityThis code indicates an issue with the electrical circuit for the battery warning lamp in vehicles equipped with dual alternators. This means the Powertrain Control Module (PCM) has detected an abnormal voltage or current in this circuit, potentially preventing the warning light from illuminating if there's a charging system problem or causing it to illuminate incorrectly.
⚠️ Before You Begin (Safety First)
Always disconnect the battery's negative terminal before performing any electrical repairs to prevent accidental shorts or injury. Use proper insulated tools when working with electrical components. Avoid touching hot engine parts. If the battery light is on and the vehicle is running, avoid unnecessary electrical loads and seek repair soon to prevent a breakdown.
Common Symptoms
- Check Engine Light (CEL) illuminated
- Battery warning lamp illuminated or flickering
- Battery warning lamp does not illuminate during ignition key-on
- Possible intermittent charging system issues
Common Causes
- Faulty wiring or connector in the battery lamp circuit
- Burnt out or faulty battery warning lamp bulb/LED
- Short circuit or open circuit in the battery lamp wiring
- Issue within the dual alternator control module or PCM affecting the lamp circuit
- Blown fuse related to the instrument cluster or charging system warning circuit
Frequently reported on: VW Touareg 2004-2010, VW Crafter 2006-2016, VW Transporter T5 2003-2015
Diagnostic Steps
- Inspect all visible wiring and connectors leading to the instrument cluster and the dual alternators for signs of damage, corrosion, or looseness.
- Check relevant fuses in the vehicle's fuse box that control the instrument cluster and charging system warning lights. Replace any blown fuses.
- If accessible, test the battery warning lamp bulb or LED for functionality. Some vehicles may require instrument cluster removal.
- Using a multimeter, test for proper voltage and continuity in the battery lamp circuit as per your vehicle's wiring diagrams.
- Clear the P1108 code after repairs and monitor if it returns.
👨🔧 When to Call a Professional
If you observe symptoms like a consistently dim or flickering battery warning lamp, or if the light does not illuminate at all during the initial key-on self-test, it's advisable to consult a professional for detailed diagnostics. These could indicate more complex wiring issues or a deeper problem within the charging system's communication with the PCM.
Commonly Asked Questions
What does P1108 mean for my VW?
P1108 indicates a malfunction in the circuit for the battery warning lamp specifically in VW vehicles equipped with a dual alternator system. It means the computer isn't seeing the expected electrical signal from this circuit.
Can I drive my car with a P1108 code?
While the code itself points to a warning lamp circuit issue, it could mask an actual charging problem. It's generally safe for short distances, but it's best to get it diagnosed soon to ensure your charging system is fully operational and you don't end up with a dead battery.
Is P1108 related to the alternator itself?
P1108 is more directly related to the *circuit* that controls the battery warning lamp, which signals an alternator issue. While it's not a direct alternator failure code, a problem with the alternator or its control module can indirectly affect this lamp circuit.
How can I diagnose a P1108 code at home?
You can start by checking all relevant fuses, inspecting wiring and connectors for visible damage or corrosion, and potentially testing the battery warning lamp bulb. A multimeter can be used to check for proper voltage and continuity in the circuit if you have access to wiring diagrams.
What if replacing the bulb or fuse doesn't fix P1108?
If basic checks don't resolve the code, the issue might be more complex, such as a broken wire, a short in the circuit, or a problem within the instrument cluster or the Powertrain Control Module (PCM). At this point, professional diagnostic tools and expertise are usually required.