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P1503

Auxillary Speed Sensor Fault.

  • Other
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
03
FaultThe specific fault in that area

What it means

P1503 is a manufacturer-specific code, and for the make 'Other' it is listed as an auxiliary speed sensor fault. The control unit has seen a missing, implausible or erratic signal from a speed sensor that is not the main engine or road speed input. The exact sensor, and what it is compared against, depends on the make, model and engine, so confirm it in the manufacturer's data for the vehicle.

Symptoms

  • Engine warning light on
  • Erratic or inoperative speedometer or related gauge
  • Rough or unstable idle
  • Reduced performance or the car entering a limited power mode
  • Poor or harsh gear changes on automatic models
  • Auxiliary equipment not working correctly, depending on the application

Possible causes

  • Damaged, contaminated or loose wiring or connector at the auxiliary speed sensorlikely
  • Faulty auxiliary speed sensorlikely
  • Damaged or dirty reluctor ring, tone wheel or pickup targetpossible
  • Incorrect air gap or loose sensor mountingpossible
  • Electrical interference or poor earth or supply to the sensor circuitpossible
  • Fault within the control unit or a related modulerare

How to diagnose

  1. Read all stored and pending codes and record the freeze frame data, noting any other speed, idle or transmission codes.
  2. Confirm in the manufacturer's data which sensor this code refers to on the vehicle, as it varies by make, model and engine.
  3. Visually inspect the sensor, its wiring and connector for chafing, heat damage, oil contamination, corrosion or poor pin tension.
  4. Check the sensor is secure and that its mounting and air gap are correct.
  5. Inspect the reluctor ring or target for damage, debris, missing teeth or excess play.
  6. Check the sensor supply, signal and earth circuits for continuity, shorts and voltage drop against the wiring diagram.
  7. Compare the live sensor data with the related speed signals while running or road testing to see if it drops out or is implausible.
  8. Check the sensor output with a suitable scope or meter against the manufacturer's specification.

How to fix

  • Repair or replace damaged wiring and clean or renew corroded connector terminals.
  • Replace the auxiliary speed sensor if it fails testing.
  • Clean, repair or replace the reluctor ring or target if it is damaged or contaminated.
  • Refit the sensor correctly and set the air gap as specified.
  • Restore poor supply or earth connections found during testing.
  • Clear the codes and retest after repair, then confirm they do not return on a road test.

Can I keep driving?

Medium severity

The car can usually be driven short distances, but book it in soon as performance or gear changes may be affected. Stop driving if it goes into a limited power mode, runs very roughly or you have lost speed readings.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

This code for other makes

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