P01B7

Code

Generic P — Powertrain

Alternative Fuel Rail Temperature Sensor Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 51 RU: 29

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Page language: EN

Causes

Open or corroded connector at the AFRT sensor
Broken, frayed, or disconnected wiring between sensor and ECU
Short to battery voltage on the sensor signal wire
Poor or missing ground or reference voltage to the sensor
Failed AFRT sensor (thermistor/element out of spec)
ECU input circuit fault or internal ECU damage

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Reduced performance or limp-home strategy on some vehicles
Hard starting or poor idle when fuel temperature compensation is required
Incorrect fuel trim or fuel delivery behavior during warm-up
Possible reduced efficiency or increased emissions during closed-loop operation

What to check

Read and record freeze frame and live data for AFRT sensor voltage/temperature
Scan for other related codes (fuel rail pressure, coolant temp, other sensor circuits)
Visually inspect AFRT sensor, connector, and harness for damage, corrosion, or contamination
Backprobe the sensor connector with key-on engine-off to measure signal voltage and reference voltage
Wiggle test wiring while monitoring live data to look for intermittent changes
Measure continuity and resistance of signal, reference and ground circuits between sensor and ECU

Signal parameters

Typical signal voltage range: ~0.1–4.9 V (varies by manufacturer) — "High" means signal near or at battery voltage
Typical expected behavior: voltage decreases as fuel temperature rises for NTC thermistors (resistance falls with higher temp)
Reference (excitation) voltage: commonly 5 V or vehicle-specific reference (measure at connector)
Expected circuit resistance: manufacturer-specific; thermistor resistance increases at lower temperatures and decreases at higher temperatures

Diagnostic algorithm

Retrieve freeze frame and note conditions when the code set (engine temp, fuel temp, battery voltage).
Verify code is current (active) and clear codes, then see if P01B7 returns during test drive.
Perform visual inspection of sensor, connector and harness for corrosion, damage, pin push-out, or fuel contamination. Repair connectors if found.
With key ON engine OFF, backprobe sensor connector: confirm reference voltage (≈5 V or vehicle-specific) and good ground. If reference or ground missing, trace to ECU or splice and repair.
Monitor sensor signal voltage during warm-up. If the signal is near battery voltage or fixed high, suspect open/short-to-B+ or failed sensor.
Measure sensor resistance at two known temperatures (cold and warmed) and compare to specification or expected thermistor behavior (resistance should change with temperature). Replace sensor if resistance does not change appropriately.
Check wiring continuity from sensor pins to ECU pins and inspect for short to battery or ground. Repair any damaged wiring or replace harness section.
If wiring and sensor test good, inspect ECU input for proper operation. Substitute a known-good ECU or perform manufacturer-specific ECU diagnostics if available.
After repairs, clear codes and perform a road test under conditions that previously caused the code to verify repair.

Likely causes

Connector corrosion or bent pins at sensor or ECU
Wiring chafed and shorting to constant battery voltage
Sensor internal short or failed thermistor element
Lost sensor reference or ground due to harness damage or poor splice

Fault status

⚠️ Status

AFRT sensor signal is higher than expected (circuit voltage above normal range) — possible open circuit, short to battery, bad sensor, poor reference/ground, or ECU input fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

Repair manuals