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GTECH Calibration
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P1579

P/N To D/R At High Throttle Angle.

  • GM
  • Powertrain
  • Manufacturer code
  • Low severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
79
FaultThe specific fault in that area

What it means

On GM vehicles P1579 means the control unit detected the transmission being shifted from Park or Neutral into Drive or Reverse while the throttle angle was high. The engine or powertrain control module logs it as a record of a harsh, high-load engagement, which is a driver-induced event rather than a component fault in most cases. It can also be set if a throttle position or range signal is misread during a normal shift.

Symptoms

  • Harsh or sudden engagement when selecting Drive or Reverse
  • Engine revving while the selector is moved out of Park or Neutral
  • Check engine light on, sometimes with no other change in driveability
  • Possible transmission shudder or clunk on engagement
  • Stored code appearing after a one-off event such as rocking the car out of a stuck position

Possible causes

  • Driver selecting Drive or Reverse with the throttle pressed or the engine held at high revslikely
  • Throttle position sensor or accelerator pedal position signal reading high or erratic at idlepossible
  • Sticking or dirty throttle body causing high idle or a raised throttle angle in Park or Neutralpossible
  • Park/Neutral position switch or transmission range signal faulty or out of adjustmentpossible
  • Wiring or connector fault on the throttle, pedal or range switch circuitsrare
  • Control module software issue, only if a known calibration update exists for the modelrare

How to diagnose

  1. Read the stored code and freeze frame data, noting throttle angle, engine speed, gear selection and vehicle speed at the time it set
  2. Ask the driver whether the car was revved or rocked between Park, Neutral, Drive and Reverse before the light came on
  3. Check for other stored codes, especially throttle, pedal, range switch or transmission codes, and deal with those first
  4. Inspect the throttle body, pedal and range switch wiring and connectors for damage, corrosion or looseness
  5. With a scan tool, watch the throttle angle and pedal readings at idle and confirm they are low, smooth and agree with each other
  6. Check that the displayed gear selection matches the lever position and that the Park/Neutral signal changes cleanly
  7. Inspect the throttle body bore for heavy deposits or sticking, noting that the procedure varies by model and engine
  8. Check for applicable service bulletins or calibration updates for the specific vehicle

How to fix

  • If it was a driver-induced event, clear the code and advise gentle selection with the foot off the throttle
  • Repair or replace damaged wiring or connectors on the throttle, pedal or range circuits
  • Clean the throttle body following the manufacturer procedure, then carry out any required relearn
  • Replace or adjust a faulty Park/Neutral or range switch
  • Replace a faulty throttle or pedal sensor assembly if its signal is incorrect
  • Apply an official calibration update only where one is known to address this code for the vehicle

Can I keep driving?

Low severity

The car can normally be driven while you book it in, provided it engages gears smoothly and no other warning lights are on. If engagement is harsh or other transmission or throttle faults appear, have it checked promptly.

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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