P01F5

Code

Generic P — Powertrain

O2 Sensor Circuit No Activity Detected Bank 1 Sensor 4

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 31 RU: 27

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Page language: EN

Causes

Open or shorted signal wire to the O2 sensor
Broken or corroded connector or pin(s)
Failed O2 sensor (no internal signal generation)
Heater circuit open or no supply (if equipped)
Blown fuse or relay for sensor heater or sensing circuit
Exhaust leak near the sensor affecting readings

Symptoms

Check Engine MIL illuminated
Possible decreased fuel economy or failed emissions test
Reduced ability of closed‑loop control to monitor catalyst efficiency
Often no obvious drivability symptoms if sensor is a downstream sensor
Possible stored related DTCs (heater or upstream sensor faults)

What to check

Scan for P01F5 and any related freeze‑frame data and pending codes
Monitor live data: compare Bank 1 Sensor 1 (upstream) vs Sensor 4 (downstream) signals
Verify sensor warm‑up and heater operation using scan tool PID (if available)
Visually inspect sensor, connector, and wiring for damage, corrosion, or deposits
Backprobe connector and check for signal voltage (engine warm) and reference/ground
Check heater supply voltage with key ON (engine OFF) and for commanded ground when running

Signal parameters

Narrowband (typical downstream): should show switching when exposed to varying exhaust or follow upstream behavior; expected ~0.1–0.9 V when active (may be steadier than upstream)
Wideband sensors: expect manufacturer's linear voltage/current protocol (refer to service literature) — typical outputs are 0–5 V or a current signal; verify with manufacturer specs
Heater circuit supply (key ON): ~11–14 V at sensor power pin if fused
Heater resistance (cold, typical): commonly ~2–20 ohms (refer to OEM spec)
Signal circuit continuity to ECM: near zero ohms to ECM input (no open); check for short to battery or ground

Diagnostic algorithm

Retrieve freeze‑frame and mode 6 data; confirm P01F5 is current and note operating conditions.
With engine at operating temperature, use scan tool to monitor Bank 1 Sensor 1 and Sensor 4 PIDs. Confirm Sensor 4 shows no activity compared with upstream sensor.
Inspect sensor and connector for contamination, broken wires, or corrosion. Repair or replace damaged connector/wires as needed.
Backprobe sensor connector: measure signal voltage while engine runs and during forced enrichment/lean events. If no signal, proceed to wiring checks.
Check heater circuit: with key ON, verify battery voltage at heater power pin; with engine running and heater commanded, verify ground switching and measure heater resistance. Replace sensor if heater open or not powered.
Perform continuity and resistance checks from sensor pins to ECM connector pins. Repair any opens, shorts, or high resistance.
Wiggle harness and connectors while monitoring live data to find intermittent faults.
If wiring and power/ground are good but no signal from sensor, replace the sensor with a correct OEM‑spec unit and clear codes. Re‑test for code return.
If fault persists after sensor replacement, check ECM input circuits and grounds; consult OEM wiring and perform component/ECM testing or replacement as required.
After repair, perform a drive cycle and verify the code remains cleared and downstream sensor activity is present.

Likely causes

Damaged wiring harness to Bank 1 Sensor 4 (chafed, pinched, rodent damage)
Connector corrosion or poor terminal contact
O2 sensor failure due to age or contamination
Heater element open or shorted
Loss of reference voltage or ground at ECM
Aftermarket or incorrect replacement sensor

Fault status

⚠️ Status

P01F5 — O2 Sensor Circuit No Activity Detected Bank 1 Sensor 4. Stored when the ECM detects no signal or no expected switching/activity from the Bank 1 Sensor 4 oxygen sensor.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2 hours