What does it mean?
P1730 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: NC Revolution Sensor Circuit Malfunction (Counter Gear Speed Sensor) .
Symptoms
- MIL (check engine lamp) on together with a transmission warning
- Erratic shift points, hunting between gears or shifts that arrive too late
- Limp mode locked in one gear after repeated signal loss
- No torque converter lockup, so engine RPM stays high at steady speed
- Speed related displays may flicker while the fault is active
Likely causes
- Failed counter gear speed sensor or a pickup covered in metallic debris
- Chipped, cracked or contaminated tone ring teeth producing a gapped signal
- Open, shorted or high resistance signal and ground wiring in the harness
- Corroded or ATF soaked sensor connector with pushed-out terminals
- Incorrect air gap or a loose sensor caused by a missing spacer or damaged mounting
- Internal transmission wear releasing swarf that disturbs the magnetic pickup
- Module input circuit failure, verified only after the wiring is proven good
How to fix it
- Compare all transmission speed sensor values on live data during a road test and look for one that drops out
- Unplug the sensor and inspect the connector for fluid, corrosion and damaged terminals
- Measure sensor resistance or capture the output waveform while turning the driveline
- Wiggle the harness along its route while monitoring live data for signal loss
- Check the signal and ground circuits for continuity and insulation faults
- Remove the sensor and examine the tip and visible tone ring teeth for debris and damage
- Replace the sensor, then inspect the transmission internals if metal was found on the tip