Code
P0735
HUMMER
P — Powertrain
Gear 5 Incorrect ratio
Views:
UK: 10
EN: 24
RU: 26
AI status
Completed
Completed
100%
Causes
- Low or degraded transmission fluid (level, contamination)
- Internal transmission wear or damage (clutches, bands, planetary set)
- Sticking or failed shift solenoid(s) or valve body defects
- Faulty input/turbine or output/speed sensors (erroneous speed signals)
- Electrical problems: damaged wiring, poor connectors, corroded terminals to TCM/solenoids
- Torque converter or clutch pack slippage
Symptoms
- Check Engine / Transmission warning lamp illuminated
- Transmission fails to shift into or hold 5th gear
- Harsh, delayed or erratic shifting into higher gears
- High engine RPMs at cruising speeds (overrevving)
- Loss of fuel economy during highway driving
- Transmission may go into limp/limit mode
What to check
- Scan for related codes and freeze frame data; read live data for gear, commanded gear, actual gear ratio, input and output speed
- Verify transmission fluid level, color and smell (burnt odor) with engine/vehicle in proper state per service manual
- Road test with data logger to observe commanded gear vs actual gear and RPM vs vehicle speed
- Inspect wiring and connectors for speed sensors, solenoids and TCM for corrosion, damage or loose pins
- Check resistance and operation of shift solenoids per manufacturer specs
- Compare measured speed sensor signals (input/turbine & output) with expected frequencies using oscilloscope if available
Signal parameters
- Engine RPM (rpm)
- Transmission input/turbine speed (rpm)
- Transmission output/speedometer speed (vehicle speed) (kph/mph or rpm-derived)
- Actual gear ratio (calculated by TCM: input/output)
- Requested/commanded gear
- Shift solenoid status (on/off or duty cycle)
Diagnostic algorithm
- Retrieve and record P0735 and any other transmission or speed-sensor codes; note freeze frame. 2) Clear codes and perform controlled road test while logging input and output speeds, commanded gear and actual gear ratio to reproduce. 3) Check transmission fluid level, condition and service history; add or replace fluid if incorrect level/condition. 4) Inspect wiring and connectors for speed sensors, solenoids and TCM for damage or poor connections; repair any faults. 5) Verify operation of input/turbine and output speed sensors: compare signals, replace sensor if out of spec. 6) Test shift solenoids for proper resistance and activation; replace solenoid(s) or valve body if stuck or out of spec. 7) If electrical and sensor systems are good, evaluate hydraulic pressure and clutch operation (line/shift pressure test). 8) If hydraulic tests show internal failures, consider transmission overhaul or replacement (inspect clutches, bands, planetary gears). 9) After repair, clear codes, perform an adaptation/learn procedure if required by manufacturer, and recheck by road test and live data logging. 10) If fault persists, consult manufacturer service information and consider TCM reflash or replacement as a last step.
Likely causes
- Low transmission fluid level or wrong fluid type
- Faulty 5th-gear shift solenoid or valve body sticking
- Worn/clutch or band related to 5th gear
- Faulty output or input speed sensor or poor signal
- Internal mechanical wear (planetary gears or clutch plates)
Fault status
Status
TCM detected that the actual transmission gear ratio in 5th gear does not match the expected ratio beyond allowable tolerance; a fault is stored and a MIL/TC warning may be set.
Repair difficulty: Hard
Diagnostic time: 2-6 hours
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