P0904
PowertrainTransmission Shifthigh severityGate Select Actuator Circuit Range/Performance
What P0904 Means
The gate select actuator signal is out of the expected range or responding poorly. The transmission may not shift smoothly or reach the correct gear position.
Symptoms
- Delayed gear engagement
- Erratic shifting
- Reduced performance
Common Causes
- Worn gate select actuator
- Wiring resistance issues
- Contaminated transmission fluid
- Faulty transmission control module
Diagnostic Steps
- Retrieve freeze frame data
- Monitor actuator position values
- Inspect wiring and connectors
- Verify fluid level and condition
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Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
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SHOP FAVORITEShop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
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