Code
P1115
PORSCHE
P — Powertrain
Heating of HO2S 1 ahead of TWC
Views:
UK: 5
EN: 9
RU: 10
AI status
Completed
Completed
100%
Causes
- Open or shorted heater circuit in the upstream O2 sensor (Bank 1 Sensor 1)
- Blown fuse, faulty relay or lost power supply to the heater circuit
- Corroded, disconnected or damaged connector or wiring (high resistance or intermittent)
- Faulty heated oxygen sensor (internal heater failed)
- Faulty engine control module (ECM) heater driver or software/parameter fault
- Excessive exhaust or engine temperatures damaging the sensor/heater
Symptoms
- Check Engine Light (CEL) illuminated
- Longer cold-start warm-up time and reduced closed-loop operation until warmed
- Possible rough idle or drivability issues until sensor warms
- Reduced fuel economy and increased emissions
- Stored freeze-frame and related misfire or fuel trim codes in some cases
What to check
- Read stored freeze-frame and live data; confirm P1115 and any related codes
- Inspect wiring and connector for the upstream O2 sensor for corrosion, damage, or disconnection
- Check relevant fuses and relays for the oxygen sensor heater circuit
- Measure battery voltage at key ON and cranking to ensure adequate supply
- Measure heater circuit voltage and continuity between connector and ECM
- Measure heater element resistance at sensor (compare to spec) and check for shorts to ground
Signal parameters
- Heater supply voltage: approx. key-ON battery voltage (0–14 V depending on system), present at heater power pin when commanded
- Heater element resistance: typically low ohms (commonly in the range of ~2–20 Ω depending on sensor design) — check OEM spec
- Heater current draw: when energized expect measurable current (hundreds of mA to a few amps depending on design)
- O2 sensor voltage (after warm-up): switching between low (~0.1 V) and high (~0.8–0.9 V) once heated and in closed-loop
- Heater control: PWM or on/off command from ECM; verify command signal present when engine cold
Diagnostic algorithm
- Retrieve and record all DTCs and freeze-frame data. Note operating conditions when P1115 set.
- Visually inspect the upstream O2 sensor, connector and wiring harness for damage, corrosion, burns or exhaust leaks nearby.
- Check relevant fuses and relays for the heater circuit; replace if blown or faulty.
- With connector disconnected, measure heater element resistance at sensor pins and compare to OEM spec; replace sensor if out of range or open/shorted.
- With ignition ON, measure voltage at the heater power pin of the sensor connector; should be battery voltage if supply is switched. If missing, trace and repair supply/fuse/relay.
- Backprobe heater ground/driver pin while commanding heater ON (engine cold with scanner or during key-on on some vehicles). Verify ECM supplies a ground or PWM signal and that current can flow.
- Check continuity from sensor connector to ECM pins to detect high resistance or opens; repair wiring or connector faults as required.
- If wiring and sensor check good but ECM does not command heater, verify ECM grounds, check for related inputs (temp sensors) and consider ECM software or module fault — consult manufacturer service info before replacement.
- After repairs, clear codes and perform road test or reproduction steps to confirm heater warms sensor and code does not return.
Likely causes
- Damaged or corroded heater power or ground connection to HO2S 1
- Failed upstream oxygen sensor heater element
- Blown fuse or faulty heater relay supplying the sensor
- High-resistance wiring/connector causing poor heater current
Fault status
Status
HO2S 1 heater malfunction (upstream of TWC) — heater circuit, sensor, wiring or supply fault detected.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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