Code
P0731
GWM
P — Powertrain
- 1 gear is not adjusted correctly
AI status
Completed
Completed
100%
Causes
- Low or contaminated automatic transmission fluid (ATF)
- Worn or burnt 1st-gear clutch pack or band
- Leaking internal transmission seals or gaskets causing hydraulic loss
- Stuck, clogged or failed shift solenoid controlling 1st gear
- Faulty valve body or valve bore wear (hydraulic control faults)
- Mechanical damage to planetary gearset or input/output gears
Symptoms
- MIL/Check Engine lamp illuminated with P0731 stored
- Harsh, delayed or slipping shifts in 1st gear
- High engine RPM with little vehicle acceleration in low speed
- Transmission stuck in a single gear, or inability to hold 1st gear
- Surging or irregular engagement when accelerating from standstill
- Transmission enters limp/failed-safe mode
What to check
- Read all stored and pending codes and capture freeze-frame data with scan tool
- Record live data while driving: commanded gear, actual gear, transmission input (turbine) and output speeds, engine RPM
- Inspect ATF level, color and smell (burnt odor); correct fluid level at operating temperature
- Road test to reproduce symptom while monitoring live transmission parameters
- Check for additional transmission-related codes (speed sensors, solenoids, line pressure)
- Visually inspect wiring harnesses and connectors for transmission speed sensors and solenoids for damage or corrosion
Signal parameters
- Engine RPM (rpm)
- Transmission input/turbine speed (rpm)
- Transmission output/vehicle speed sensor (km/h or mph and rpm)
- Commanded gear vs actual gear (TCM values)
- Shift solenoid status and current (mA) or duty cycle (%)
- Measured transmission line pressure (kPa/bar/psi)
Diagnostic algorithm
- Retrieve all codes and freeze-frame data. Note whether other transmission codes are present.
- Check ATF level, condition and service history. If fluid is low or severely degraded, correct level and retest.
- Clear codes and perform a controlled road test while monitoring live data: watch commanded vs actual gear, input and output speeds, and note when code sets.
- Verify speed sensor inputs and wiring: inspect connectors, measure sensor outputs and resistances, and compare to spec.
- Test shift solenoid(s): check electrical continuity/resistance, apply actuator test with scan tool and observe hydraulic response.
- Measure transmission line pressure at the correct test port(s) per vehicle manual. Compare with expected values through shift and during first-gear apply.
- If hydraulic pressure or solenoid control is out of range, inspect valve body: remove pan, check valve bores, filters/screens and solenoid operation; replace or repair as indicated.
- If valve body and hydraulics check good, suspect internal wear: clutch pack, band or planetary gear damage—perform transmission teardown and inspect components.
- If mechanical repairs are made, replace damaged parts, reassemble with correct procedures and use OEM torque specs; refill with correct ATF and perform TCM adaptations/relearn procedures.
- After repairs, clear codes and verify by road test and live-data monitoring to confirm correct 1st-gear ratio and no return of fault.
Likely causes
- Low ATF level or degraded fluid leading to poor clutch apply
- Worn 1st gear clutch pack or band causing slip and wrong ratio
- Sticking or failed shift solenoid for 1st gear circuit
- Valve body internal leak or bore wear reducing apply pressure
- Faulty input (turbine) or output speed sensor giving incorrect ratio calculation
Fault status
Status
P0731 — Incorrect 1st gear ratio detected. The transmission control module reports the actual ratio for 1st gear is outside expected limits; could be hydraulic, mechanical or control-related.
Repair difficulty: Hard
Diagnostic time: 3-10 hours
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