P1103 VOLKSWAGEN – Heater O2 Sensor Circuit, Bank 1 Sensor 1 Voltage Too Low

📌 Meaning of VW P1103 Code

The P1103 code for a Volkswagen vehicle refers to a problem with the heated oxygen sensor (HO2S) located before the catalytic converter (bank 1, sensor 1). This sensor measures the oxygen content in exhaust gases to adjust the air/fuel mixture.

The “low voltage” message from the heater circuit means the heating element integrated into the sensor is not receiving or consuming enough current. This can prevent the sensor from quickly reaching operating temperature, delaying engine regulation in “closed-loop” mode, thus affecting fuel efficiency and emissions.

⚠️ Possible Symptoms

✅ Check Engine light on
🚗 Unstable idle
🛢️ Excessive fuel consumption
❌ Increased pollutant emissions
🔄 Slow lambda sensor response time

🛠️ Possible Causes of VW P1103 Code

Faulty oxygen sensor (HO2S 1/1) – The heating element resistance may be too high or the sensor may be completely out of service.
Blown fuse – Some HO2S sensor circuits are protected by a dedicated fuse.
Open or shorted wiring – Damaged wiring between the sensor and control module (abrasion, heat, etc.).
Poor electrical connection – Corroded, poorly connected, or broken terminals at the sensor or PCM connector.
Faulty PCM – Rare, but the engine control module may not provide the control voltage to the heater circuit.

✅ How to Fix Volkswagen P1103 Code

🔧 Step 1: Visual Inspection

Locate the O2 sensor upstream of the catalytic converter on bank 1 (cylinder 1 side).
Check the sensor wires: look for signs of burning, cutting, or rubbing.
Inspect the connectors: look for corrosion, loose or deformed pins.

🧪 Step 2: Sensor Check

With a multimeter, test the heater circuit resistance (usually between 4 to 10 ohms according to manufacturer specifications).
No continuity = burned-out heater → replace the sensor.

⚡ Step 3: Check Power Supply

Ignition on, check that there is 12 V at one of the heater pins on the connector (according to manufacturer diagram).
If no voltage → check the fuse or PCM output (depending on the model).

🔄 Step 4: Replacement and Test

Replace the sensor if faulty.
Clear the error code with an OBD-II tool.
Start the engine, let it warm up, and see if the code returns.

📚 Notes

It is crucial to only use O2 sensors compatible with VW, as universal sensors can cause incorrect readings.
Do not overlook fuses: a simple blown fuse can cause this code.
If the code reappears despite sensor replacement, suspect a deep wiring issue or PCM module problem.