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DTC codes / GM codes / P1579

P1579 · GMP/N To D/R At High Throttle Angle

P1579 on GM vehicles indicates that the powertrain control module (PCM) has detected an implausible signal from the park/neutral (P/N) to drive/reverse (D/R) switch when the throttle angle is high. The PCM expects the transmission range switch to report a change from Park or Neutral to Drive or Reverse only when the throttle is at a low angle, and a high throttle angle during this transition suggests a faulty switch, wiring issue, or misadjusted linkage.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The check engine light or service engine soon light illuminates on the instrument cluster.
  • The engine may hesitate or stumble when shifting from Park or Neutral into Drive or Reverse.
  • In some cases, the transmission may not engage smoothly or may exhibit delayed engagement.
  • The vehicle may enter limp mode or exhibit reduced power if the PCM limits throttle response.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.

Common causes, most likely first

  1. Faulty park/neutral to drive/reverse switch (transmission range sensor) sending incorrect signals.
  2. Wiring harness damage or corrosion at the switch connector or PCM connector.
  3. Misadjusted or loose shift linkage causing the switch to report an incorrect range.
  4. Internal transmission mechanical issues affecting range detection.
  5. PCM software glitch or internal fault (rare).
  6. Aftermarket accessories or improper electrical modifications interfering with the circuit.

How to diagnose and fix it

  1. Connect a scan tool and verify the P1579 code is current; check freeze frame data for throttle angle and range switch status.
  2. Inspect the transmission range switch connector and wiring for corrosion, chafing, or loose pins; repair as needed.
  3. Check the shift linkage adjustment and ensure the switch is properly aligned in Park and Neutral.
  4. Test the range switch with a multimeter for continuity in each gear position according to the service manual.
  5. If the switch fails testing, replace the park/neutral to drive/reverse switch and clear the code.
  6. Clear the code and perform a road test to verify the repair; recheck for pending codes.
  7. If the code persists, diagnose the PCM and circuit with a professional scan tool and oscilloscope.

Don't overlook the range switch linkage

  • A common misdiagnosis is replacing the PCM when the actual fault is a worn transmission range switch or corroded connector.
  • The code can set intermittently due to a loose shift cable that momentarily misaligns the switch during aggressive driving.
  • High throttle angle during Park/Neutral to Drive/Reverse engagement is often caused by drivers revving the engine while shifting, which can trigger the code even with a healthy switch.
  • Aftermarket remote start systems or alarm installations that tap into the range switch circuit can cause false P1579 codes.
  • Always check for related codes like P0705 or P0706 before condemning the switch, as they may indicate a broader circuit issue.

Can I keep driving with P1579?

If the vehicle drives normally and the only symptom is the warning light, you can drive cautiously to a repair shop, but avoid aggressive throttle during gear engagement. If the transmission exhibits harsh shifting or fails to engage, stop driving and have the vehicle towed to prevent further damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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