P2429

Fuel Temperature Sensor B Circuit High

P2429 is a generic OBD-II powertrain diagnostic trouble code: Fuel Temperature Sensor B Circuit High. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2429
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
Need P2429 disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P2429 means

P2429 indicates that the PCM has detected a high-voltage signal from the fuel temperature sensor B circuit. Fuel temperature sensors are used in fuel injection systems, particularly diesel common-rail systems, to compensate fuel delivery calculations for the effect of temperature on fuel density and viscosity. Sensor B refers to a second fuel temperature sensor in systems that use more than one.

A circuit-high fault on a temperature sensor typically indicates a short to voltage on the signal wire, an open in the sensor ground circuit causing the signal to float high, or a failed sensor element that has gone to high resistance. In most sensor configurations, high resistance or an open circuit will drive the signal to the supply rail, which the PCM interprets as an implausibly cold reading. The PCM will substitute a default fuel temperature value and may set a fuel trim or injection quantity fault alongside this code.

Diagnosis begins with inspecting the sensor connector and harness, then measuring the sensor resistance at a known temperature against the manufacturer specification. Verify ground circuit integrity before condemning the sensor.

Common causes

Most-frequently reported root causes when P2429 is logged.

  • 1
    Open circuit in the sensor ground wire causing the signal to float toward supply voltage.
  • 2
    Short to voltage in the sensor signal wire.
  • 3
    Failed fuel temperature sensor B with high or open internal resistance.
  • 4
    Corroded or backed-out sensor connector terminal.
  • 5
    Damaged wiring harness in the fuel system routing area.
  • 6
    PCM input circuit fault misreading the sensor signal.
  • 7
    Fuel filter housing or rail fitting damage disturbing the sensor mounting and connection.

Symptoms drivers notice

MIL on with P2429 stored.
PCM substituting a default fuel temperature value, potentially affecting cold-start fueling.
Possible hard or rough cold start if the substituted value is inaccurate.
Companion fuel delivery or trim codes may be present.
No drivability impact when engine is fully warm in mild conditions.

How to diagnose P2429

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs and freeze-frame data; note the indicated fuel temperature at fault set.
  2. 2
    Inspect the fuel temperature sensor B connector and harness for damage or corrosion.
  3. 3
    Measure the sensor resistance at the connector with the harness unplugged; compare to the temperature-resistance specification for the current ambient temperature.
  4. 4
    Verify the sensor ground circuit has continuity back to the PCM ground.
  5. 5
    Check the signal wire for shorts to voltage.
  6. 6
    If the sensor resistance is out of specification, replace the sensor and clear codes.
  7. 7
    Confirm repair with a test drive including a cold-start cycle and verify no codes return.

Vehicles where we've handled P2429

Platforms in our catalogue with confirmed P2429 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

What does the fuel temperature sensor actually do?

It allows the PCM to correct the calculated fuel mass for temperature-related density changes, ensuring accurate injection quantities especially at fuel temperature extremes.

Can P2429 cause poor fuel economy?

Potentially. If the PCM is using an inaccurate default value that does not match actual fuel temperature, injection timing or quantity may be slightly off optimal.

Is sensor B always in the fuel rail?

Not necessarily. Sensor B location varies by manufacturer and may be in the fuel return line, fuel filter housing, or low-pressure supply circuit. Consult the vehicle wiring diagram.

Can I drive with P2429?

The vehicle will typically remain drivable using a substitute value, but diagnosing and repairing the fault is recommended to restore accurate fuel management.

Disabling P2429 in software

RaceTune can permanently disable P2429 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECUs with a P2429 disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch EDC17C50 verified 1 software version

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

Got P2429 in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file