P05AF

Brake Pedal Position Sensor A Circuit Low

P05AF is a generic OBD-II powertrain diagnostic trouble code: Brake Pedal Position Sensor A Circuit Low. 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
P05AF
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P05AF means

P05AF is set when the control module detects that the voltage signal from brake pedal position sensor A is below the minimum expected threshold. Brake pedal position sensors are typically analog voltage-output devices; a low circuit reading suggests a short to ground on the signal wire, loss of the sensor reference voltage supply, or an internally failed sensor.

Because brake pedal position data is used by multiple safety-related systems including traction control, stability control, transmission shift logic, and autonomous emergency braking, a low circuit fault may cause the module to disable or limit those features as a precaution. The brake hydraulics are generally unaffected, so stopping ability is preserved, though some vehicles may restrict powertrain performance.

Diagnosis should confirm whether the low voltage is in the wiring or within the sensor. Disconnecting the sensor connector and observing whether the signal voltage rises toward the reference level helps isolate the sensor from the wiring. Reference voltage and ground integrity at the sensor connector should be verified before any parts are replaced.

Common causes

Most-frequently reported root causes when P05AF is logged.

  • 1
    Brake pedal position sensor A internally shorted to ground.
  • 2
    Signal wire shorted to ground between the sensor and the control module.
  • 3
    Loss of the reference voltage supply to sensor A.
  • 4
    Corroded sensor A connector creating a leakage path to ground.
  • 5
    Damaged wiring harness near the brake pedal assembly.
  • 6
    Moisture intrusion into the sensor body causing an internal short.
  • 7
    Control module reference circuit fault.

Symptoms drivers notice

MIL and possibly a brake system warning light illuminated.
Stability control, traction control, or ABS warning lights may also illuminate.
Driver assistance features such as automatic emergency braking may be disabled.
Normal brake pedal feel and stopping ability are generally retained.
Possible reduced powertrain performance or torque limiting on some vehicles.

How to diagnose P05AF

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs from all modules and record freeze frame data.
  2. 2
    With the key on and engine off, measure the signal voltage at sensor A connector.
  3. 3
    Check the reference voltage and ground at the sensor A connector.
  4. 4
    Disconnect sensor A and observe whether the signal voltage rises toward the reference level.
  5. 5
    If voltage rises after disconnecting, the sensor is likely shorted internally and should be replaced.
  6. 6
    If voltage remains low after disconnecting, inspect the signal wire for a short to ground.
  7. 7
    Inspect the harness routing near the brake pedal pivot for chafing or pinching.

Related powertrain codes

Frequently asked questions

Does P05AF mean my brakes are failing?

No. P05AF is an electrical fault in the brake pedal position sensor circuit, not a hydraulic failure. Your brake pedal and stopping ability are not directly affected.

How does a short to ground cause a low voltage reading?

When the signal wire is unintentionally connected to ground, it pulls the sensor output toward zero regardless of pedal position, so the module reads a below-minimum value.

Can P05AF and P05AE appear together?

Yes. If sensor A reads low or zero, it will also fail to correlate with a normally operating sensor B, so both codes may be stored at once.

Is brake pedal position sensor A replaceable separately?

On most vehicles the sensor mounts on the brake pedal bracket and can be replaced independently. Some integrated pedal assemblies require replacing the whole pedal box.

Disabling P05AF in software

RaceTune can permanently disable P05AF — 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.

ECU families we can disable P05AF on

We hold the DaVinci A2L disable definitions for these families, so the exact P05AF path and mask addresses are mapped. verified marks a confirmed disable definition. We support many more — upload your file and our identifier will match it automatically.

  • Bosch EDC17C74 verified
  • Bosch MD1CP002 verified
  • Bosch MD1CP004 verified
  • Bosch MD1CS001 verified

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.

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