P1657 — 1-4 Upshift Solenoid Control Circuit

Causes

• Open or short in the 1-4 upshift solenoid wiring (including harness chafing)
• Corroded, loose or damaged connector at the solenoid or transmission control module
• Faulty 1-4 upshift solenoid (coil shorted or open)
• Faulty transmission control module (TCM) or PCM output driver
• Blown fuse or poor battery/ignition power supply to TCM/solenoid circuit
• Internal transmission hydraulic/mechanical fault preventing correct solenoid response (less common)

Symptoms

• MIL (Check Engine) lamp illuminated
• Harsh, delayed or missing 1→4 upshift; transmission may be stuck in lower gear or limp mode
• Erratic shifting or reduced performance
• Possible transmission slipping or inability to reach higher gears
• Stored transmission-related freeze frame data or additional transmission codes

What to check

• Read freeze frame and stored codes; note any related transmission codes
• Visual inspection of wiring and connectors for damage, corrosion, or bent pins at the transmission and TCM/PCM
• Check battery voltage and charging system; ensure good system voltage
• Inspect related fuses and relays for the transmission/TCM power and ground
• Measure solenoid coil resistance and compare to specification
• Check for continuity between the TCM/PCM control pin and the solenoid connector; test for shorts to ground or battery

Signal parameters

• Typical solenoid coil resistance: commonly ~10–50 ohms (manufacturer-specific). Compare with service spec for exact value.
• Control signal: PWM output from TCM/PCM. When commanded ON the driver switches to ground, producing pulsed current.
• Expected command voltage: pulse referenced to battery voltage; when OFF the control line may be pulled high by device circuitry.
• When commanded ON: current should flow through solenoid (measure voltage across coil or current draw).
• No short to battery (low resistance to B+) or short to ground when circuit is OFF; open circuit indicates broken wire or connector.

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