Code
P1190
VOLKSWAGEN
P — Powertrain
Linear Oxygen Sensor Reference Voltage Incorrect Signal
Views:
UK: 26
EN: 42
RU: 39
AI status
Completed
Completed
100%
Causes
- Open, short or intermittent wiring in the sensor reference/supply or ground circuit
- Corroded or loose sensor connector or pins
- Blown fuse or loss of ECU reference/supply power
- Failed linear (wideband) oxygen sensor
- Water or contamination in sensor connector
- Faulty ECU/PCM or internal driver fault
Symptoms
- Check Engine Light (MIL) ON
- Poor idle, hesitation or drivability issues
- Reduced fuel economy and increased emissions
- Failed emissions/inspection test
- Stored or pending O2/sensor related codes
What to check
- Read and record stored codes, freeze frame and live O2 sensor data with a capable scan tool
- Visually inspect sensor harness and connector for corrosion, pin damage, water ingress or heat/abrasion damage
- Check related fuses and power feeds to the ECU/sensor circuit
- Backprobe the sensor connector with ignition ON (engine OFF) and measure reference/supply voltage and ground continuity
- Wiggle harness while monitoring live data for intermittent faults
- Measure heater resistance and apply battery voltage (where safe/spec’d) to confirm heater circuit integrity
Signal parameters
- Sensor reference/supply is typically provided by the ECU — expected supply is usually ~5.0 V (± ~0.25 V) on many vehicles; consult VW service data for exact value
- Linear O2 sensor output is an analog signal — some sensors output 0–5 V, others use a low-voltage range; consult OEM specs for expected range and stoichiometric output
- Heater circuit is normally driven by battery voltage through a relay/fuse — heater resistance and current vary by sensor model (check OEM spec sheet)
Diagnostic algorithm
- Retrieve all codes and freeze-frame data; note whether code is current or intermittent.
- Perform a thorough visual inspection of the linear O2 sensor wiring harness and connector for corrosion, bent pins, water, heat damage or repairs.
- Check fuses and relays supplying the ECU and sensor circuits; repair any blown fuses or poor contacts.
- Backprobe the sensor connector with ignition ON (engine OFF). Measure the reference/supply voltage at the ECU feed and compare to OEM spec (typically ~5V). Verify a solid ground/ref return.
- Inspect continuity between the sensor connector and the ECU for the reference, signal and ground circuits. Repair any opens/shorts.
- With a scan tool, monitor the linear O2 sensor live data while doing a wiggle test of the harness and while warming the engine. Look for erratic or out-of-range values.
- Measure heater resistance and verify heater operation/power; replace sensor if heater circuit is dead and wiring/fuse is good.
- If wiring, connector and power/ground checks are good, replace the linear oxygen sensor with the correct OEM or approved replacement unit and clear codes.
- If the code returns after sensor replacement and wiring checks, suspect ECU/PCM fault — check for technical service bulletins and consider ECU bench testing or replacement as last resort.
Likely causes
- Connector corrosion or damaged wiring at the linear O2 sensor
- Lost supply/reference voltage from ECU (blown fuse or open supply)
- Bad ground connection for the sensor reference or return
- Failed linear oxygen sensor (internal electronics)
- Intermittent wiring due to chafing or broken conductor
Fault status
Status
Linear oxygen sensor reference voltage out of range or incorrect signal. Inspect sensor supply, reference and ground circuits, connector and sensor; ECU fault less common but possible.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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