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DTC codes / GM codes / P1657

P1657 · GM1-4 Upshift Solenoid Control Circuit

P1657 on a GM vehicle means the powertrain control module (PCM) has detected an electrical fault in the control circuit for the 1-4 upshift solenoid inside the automatic transmission. The PCM commands the solenoid to redirect hydraulic pressure for the 1-4 shift, and it monitors the circuit for expected voltage or current; when the feedback falls outside the expected range, it stores this code and may disable the shift strategy.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyProfessional
AreaComputer and output circuits

Symptoms you may notice

  • Check engine light or transmission warning light illuminated on the instrument cluster
  • Harsh or delayed 1-4 upshift, or the transmission may stay in a lower gear longer than normal
  • Transmission may default to a limp-home mode with firm or erratic shifting
  • Poor fuel economy on the highway because the 1-4 shift is inhibited
  • Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

  1. Damaged or corroded wiring harness connector at the transmission pass-through or solenoid body
  2. Open or shorted 1-4 upshift solenoid coil inside the transmission valve body
  3. Chafed or broken wire between the PCM and the transmission connector
  4. Faulty transmission control module (TCM) or PCM driver circuit, though less common
  5. Internal transmission mechanical wear causing the solenoid to draw abnormal current
  6. Contaminated transmission fluid or a sticking valve body affecting solenoid operation

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data to confirm P1657 is current and not history
  2. Inspect the transmission wiring harness and connectors for corrosion, chafing, or loose pins
  3. Measure the resistance of the 1-4 upshift solenoid at the transmission connector and compare to the GM service specification
  4. Check for battery voltage and ground continuity on the control circuit from the PCM to the solenoid
  5. If the circuit tests good, remove the transmission pan and inspect the solenoid and valve body for debris or damage
  6. Replace the faulty solenoid or repair the wiring as needed, then clear the code and verify the 1-4 shift with a road test
  7. Perform a transmission adaptive relearn if the repair involved solenoid replacement or valve body service

What the 1-4 solenoid code hides

  • A loose or corroded ground connection at the transmission case can mimic a failed solenoid and set P1657 without any internal fault.
  • The 1-4 upshift solenoid is often confused with the 1-2 shift solenoid; on many GM units they share a connector, so a single damaged pin can set multiple codes.
  • Intermittent P1657 that appears only when hot often points to a solenoid coil that breaks down with temperature, not a wiring issue.
  • A low or dirty transmission fluid level can cause the PCM to see abnormal solenoid current and set this code even when the solenoid itself is good.
  • Replacing the solenoid without checking the valve body for sticking valves can lead to a repeat failure and the same code returning.

Can I keep driving with P1657?

You can usually drive the vehicle to a repair shop, but avoid heavy acceleration and highway speeds because the 1-4 shift may be disabled and the transmission could enter limp mode. If shifting becomes harsh or the vehicle slips, stop driving and have it towed to prevent internal 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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