SSA Inductive Signature Malfunction
Your engine's crankshaft position sensor isn't producing a clean, readable signal—like trying to read a barcode that's smudged or damaged. The ECU can't properly synchronize ignition timing because it can't reliably detect engine speed.
The ECM monitors the inductive signature from the crankshaft position sensor, which generates a voltage waveform as engine teeth pass the sensor. The ECU analyzes signal amplitude, frequency, and rise-time to confirm proper engine synchronization. If the waveform degrades or falls outside acceptable parameters, a fault is set.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Signal Amplitude | 0.5–5.0 volts peak-to-peak | Below 0.5V or erratic fluctuation |
| Signal Rise-Time | < 1 microsecond transition | > 2 microseconds or unstable slope |
Code P1720 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P1720 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.