Skip to content
GTECH Calibration
Portal

P1501

Vehicle Speed Sensor Circuit Intermittent.

  • GMC
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
01
FaultThe specific fault in that area

What it means

P1501 on a GMC means the powertrain control module has seen the vehicle speed sensor signal drop out, become erratic or disappear intermittently while the vehicle was moving. The signal did not agree with other inputs such as engine speed, load or transmission output speed, or it was briefly lost and then returned. Because the fault comes and goes, it is often linked to wiring, connectors or the sensor itself.

Symptoms

  • Speedometer jumping, dropping to zero or reading erratically
  • Cruise control cutting out or not engaging
  • Harsh, delayed or inconsistent automatic gearbox shifts
  • Torque converter clutch not locking or locking erratically
  • Rough or unstable idle when slowing to a stop
  • Malfunction indicator lamp on, possibly with ABS lamp or other warning lamps

Possible causes

  • Damaged, chafed or corroded wiring to the vehicle speed sensorlikely
  • Loose, corroded or contaminated connector at the speed sensor or control unitlikely
  • Failing vehicle speed sensor or output speed sensor (type and location depend on model and gearbox)likely
  • Metal debris on the sensor tip or damaged reluctor or tone ringpossible
  • Fault in the ABS wheel speed signal or module supplying the speed signal (depends on model)possible
  • Instrument cluster or intermediate module fault affecting the speed signalrare
  • Internal powertrain control module faultrare

How to diagnose

  1. Read all stored and pending codes and record the freeze frame data to see speed, load and engine speed when the fault set
  2. Check for other related codes, especially ABS, transmission or wheel speed sensor faults, and deal with those first
  3. Compare the scan tool vehicle speed reading with the actual road speed on a test drive and watch for dropouts
  4. Inspect the sensor, its wiring and connectors for chafing, heat damage, water ingress, corrosion and bent or pushed-back pins
  5. Wiggle test the harness and connector with the engine running or the drive wheels raised safely, watching for the speed signal to drop out
  6. Check the sensor tip for metal debris and the reluctor or tone ring for damage or missing teeth
  7. Test the sensor supply, ground and signal circuits against the manufacturer's specification for your model and sensor type
  8. Check for continuity and short circuits in the signal wire back to the control unit

How to fix

  • Repair or replace damaged wiring and secure it away from heat and moving parts
  • Clean or replace corroded connectors and terminals and ensure they latch fully
  • Replace the vehicle speed sensor or output speed sensor if it fails testing
  • Clean debris from the sensor and replace a damaged reluctor ring or tone ring
  • Repair the ABS wheel speed or speed signal source if it is the cause
  • Repair or replace the control unit only after wiring and sensors have been proven good

Can I keep driving?

Medium severity

The car can usually be driven short distances, but erratic gearbox shifting and loss of cruise control may get worse. Have it checked soon, and avoid it altogether if the gearbox is shifting harshly or the ABS lamp is also on.

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

This code for other makes

Nearby codes