Heater circuit wiring shorted to a live feed (chafed or damaged insulation near the exhaust or engine bay); Faulty upstream oxygen sensor with an internal heater short; Damaged, corroded or contaminated sensor connector or terminals; Fault in the heater supply or control, such as a relay or fuse circuit feeding the heater (depends on model and engine); Engine control unit output driver fault; Previous repair damage to the loom, such as pinched or mis-routed wiring.

P1103

Oxygen Sensor Heating Circuit Bank 1 Sensor 1 Short To B+.

Volkswagen
Powertrain
Manufacturer code
Low severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
1: AreaFuel and air metering
03: FaultThe specific fault in that area

What it means

On Volkswagen vehicles, P1103 means the engine control unit has detected the heater circuit of the upstream oxygen sensor (Bank 1 Sensor 1) is shorted to battery positive. The control unit drives the heater and monitors the circuit, and it saw a voltage on the heater control line that should not be there. The heater is needed to bring the sensor up to working temperature quickly, so fuel control may fall back to a less accurate mode.

Symptoms

Engine management light on
Rough or unstable idle, especially after a cold start
Slightly increased fuel consumption
Poor cold-running or hesitation while the sensor is not in closed loop
Failed emissions test or other oxygen sensor related codes stored

Possible causes

Heater circuit wiring shorted to a live feed (chafed or damaged insulation near the exhaust or engine bay)likely
Faulty upstream oxygen sensor with an internal heater shortlikely
Damaged, corroded or contaminated sensor connector or terminalspossible
Fault in the heater supply or control, such as a relay or fuse circuit feeding the heater (depends on model and engine)possible
Engine control unit output driver faultrare
Previous repair damage to the loom, such as pinched or mis-routed wiringrare

How to diagnose

Read all stored codes and freeze frame data, and note whether other oxygen sensor or fuel trim codes are present
Visually inspect the Bank 1 Sensor 1 wiring and connector for melted, chafed or pinched insulation, particularly near the exhaust manifold or downpipe
Check the connector for corrosion, water ingress, bent or pushed-back terminals
Using the correct wiring diagram for the model and engine, identify the heater feed and control pins
With the ignition off and the sensor unplugged, test the heater wiring for any short to battery positive and check the heater resistance against the specification
With the sensor unplugged and ignition on, check the heater control line for unexpected voltage at the connector
Check the relevant fuse and any heater supply relay or feed for the correct operation as per the wiring diagram
Clear the code and road test, then recheck live data to confirm the fault does not return

How to fix

Repair or replace the damaged section of wiring and secure it away from heat and sharp edges
Replace the upstream oxygen sensor if the heater is shorted or out of specification
Clean or repair the connector terminals, or replace the connector if corroded or damaged
Repair or replace the faulty relay or supply circuit component identified by testing
Replace or repair the engine control unit only after wiring and sensor faults have been fully ruled out

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this is mainly a fuel control and emissions concern. Book it in soon, as running without proper sensor control can raise fuel use and may stress the catalytic converter over time.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.