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Home / DTC / P0785 — - Solenoid fault

P0785 — - Solenoid fault

Detailed page for trouble code P0785.

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Code

P0785

GWM P — Powertrain

- Solenoid fault

Brand: GWM
Type: P — Powertrain
Views: UK: 1 EN: 2 RU: 2
AI status
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Page language: EN

Causes

  • Failed shift solenoid (coil open or shorted)
  • Damaged or chafed wiring harness to the solenoid (open, short to ground or battery)
  • Corroded or loose connector pins or poor grounding
  • Blown fuse or faulty transmission relay affecting solenoid power
  • Contaminated or low transmission fluid causing valve/solenoid sticking
  • Valve body internal fault or hydraulic blockage

Symptoms

  • MIL/Check Engine light illuminated
  • Transmission shifts harshly, erratically, or slips
  • Transmission stuck in one gear or in limp (failsafe) mode
  • Delayed or no upshift/downshift
  • Possible transmission fluid leakage or abnormal fluid color/smell

What to check

  • Read freeze frame and all stored transmission codes with a scan tool; capture live data while attempting to shift
  • Inspect transmission fluid level and condition (color, odor, contamination)
  • Visually inspect the solenoid connector(s), pins and harness for corrosion, damage or moisture
  • Check related fuses and relays for continuity and proper operation
  • Measure battery voltage at key-on and while cranking to ensure adequate supply
  • Perform wiggle test on wiring while monitoring live data for intermittent changes

Signal parameters

  • Solenoid coil DC resistance: should be within manufacturer specification (typical range for many transmissions ~10–50 ohms). Refer to service data for exact value.
  • Connector/key-on voltage: approximately battery voltage (~12 V) at the power feed; control side is switched or PWM from TCM.
  • Command signal: TCM typically uses a switched ground or PWM to control solenoid (duty cycle and frequency are model-specific; typical PWM frequencies range from ~20–300 Hz).
  • Expected behavior: when commanded ON, controller will pull/drive the solenoid; measured voltage/current should change accordingly and coil resistance should be stable (not open or shorted).
  • Continuity: good continuity between solenoid pin and TCM pin; no short to ground or to battery feed

Diagnostic algorithm

  1. Connect a diagnostic scanner and confirm P0785; note freeze-frame and any additional transmission or electrical codes.
  2. Check transmission fluid level/condition; top/replace fluid if contaminated and continue diagnosis.
  3. Visually inspect the solenoid connector and harness for damage, corrosion, or moisture. Repair any obvious issues.
  4. With ignition off, disconnect solenoid connector and measure DC resistance of the solenoid coil at the solenoid terminals. Compare to spec. If open or shorted, replace the solenoid.
  5. With connector disconnected, check for battery voltage on the power feed and for continuity to ground on the control side as directed by service manual. Verify there is no short to battery or ground.
  6. Backprobe the solenoid connector with key on (engine off) and command the solenoid on/off with the scan tool; observe voltage, duty cycle and response in live data. Look for switching or PWM from the TCM and correct voltage levels.
  7. Perform harness continuity check between solenoid connector and TCM connector; check for shorts to ground or battery.
  8. If wiring and solenoid check good but fault persists, consider bench-testing or replacing the solenoid, inspecting valve body for internal faults, and retesting.
  9. If multiple solenoids or circuits show issues or if TCM outputs are out of specification, evaluate the TCM (or PCM) and its grounds/power supplies; replace only after confirming upstream driver fault.
  10. Clear codes and road-test to verify repair. Re-scan to ensure code does not return.

Likely causes

  • Solenoid coil failure or intermittent internal connection
  • Connector corrosion or poor pin contact at the transmission harness
  • Broken wire or splice between TCM and solenoid
  • Low/dirty transmission fluid causing electrical/operational issues

Fault status

⚠️ Status
Electrical fault detected in a transmission shift solenoid circuit (P0785). Possible open/short, poor connector, wiring damage, or solenoid failure. Further electrical and hydraulic checks required.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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