P1105
ToyotaP1105 indicates a fault detected in the upper alternator circuit or the upper alternator itself, specific to Toyota vehicles equipped with a dual alternator system.
High SeverityThis code signifies that your Toyota's engine control module has detected an issue with the upper alternator's charging output or its control circuit in a dual alternator setup. This typically means the vehicle's electrical system may not be receiving adequate power, potentially leading to a drained battery and vehicle breakdown.
⚠️ Before You Begin (Safety First)
Always disconnect the battery's negative terminal before working on any electrical components. Ensure the engine is off and cool. Wear appropriate safety gear, including gloves and eye protection, when handling automotive fluids or components.
Common Symptoms
- Battery warning light illuminated on the dashboard
- Dim headlights or interior lights
- Slow or no crank condition
- Malfunctioning electrical accessories
- Engine stalling or rough idle
Common Causes
- Faulty upper alternator
- Wiring harness issues (chafed, corroded, or open circuit) leading to the upper alternator
- Blown fuse in the charging system related to the upper alternator
- Faulty alternator control module (if applicable)
- Malfunctioning Engine Control Module (ECM) (rare)
Frequently reported on: Toyota Tundra (2007-2015), Toyota Sequoia (2008-2016), Toyota Land Cruiser (2008-2014)
Diagnostic Steps
- Inspect the battery terminals for corrosion and ensure they are tight.
- Test the battery voltage with a multimeter, ensuring it holds a charge (should be around 12.6V when off).
- Visually inspect the wiring harness connecting to the upper alternator for any signs of damage, fraying, or loose connections.
- Check all relevant fuses in the under-hood fuse box related to the charging system. Consult your owner's manual for fuse locations.
- If accessible, check the belt tension for the upper alternator to ensure it's not slipping or damaged.
👨🔧 When to Call a Professional
If after checking basic connections and battery health the code persists, or if you notice additional electrical system warnings or complete power loss, it's time to consult a professional mechanic for advanced diagnostics and repair.
Commonly Asked Questions
What does P1105 mean for my Toyota?
P1105 indicates a problem with the upper alternator or its control circuit in your Toyota, specifically if it has a dual alternator system.
Can I drive my vehicle with a P1105 code?
It is not recommended to drive with this code, as a failing alternator can lead to a dead battery, leaving you stranded and potentially damaging other electrical components.
How do I identify the 'upper' alternator?
In vehicles with dual alternators, the 'upper' alternator is typically mounted higher than the 'lower' one. Consult your vehicle's service manual or a diagram specific to your model for precise identification.
What are the most common fixes for a P1105 code?
The most common fixes involve inspecting and repairing wiring, checking fuses, ensuring the battery is healthy, and ultimately, replacing a faulty upper alternator if diagnosed as the cause.
Is the P1105 code serious?
Yes, it is considered a serious code because it directly impacts the vehicle's charging system, which is vital for engine operation and powering all electrical accessories.