P1780low severityPowertrain
Transmission Control Switch Circuit
on 1998 Mazda MPV 3.0L V6 · FWD
What this code means
The PCM has detected a malfunction in the transmission control switch circuit. This switch allows the driver to select between different transmission operating modes such as sport, economy, or winter mode.
Symptoms
- Check Engine Light
- Transmission mode selection not working
- Stuck in one transmission mode
- Mode indicator light malfunction
Common causes
- Faulty transmission mode switch
- Wiring issue in switch circuit
- Corroded switch connector
- PCM input circuit fault
- Switch mounting issue
Diagnostic steps
- Check transmission mode switch signal on scan tool while pressing switch
- Inspect switch connector for corrosion
- Test switch continuity in each position
- Check wiring between switch and PCM
- Verify PCM receives switch signal
Repair notes
Replace the transmission control switch if it does not change states properly.
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