Timing Reference High Resolution Signal B No Pulses
The engine's computer isn't receiving any signal pulses from the camshaft position sensor B, similar to a clock that suddenly stops ticking. Without this timing reference, the engine can't properly synchronize fuel injection and ignition.
The ECM monitors the Camshaft Position Sensor B for a high-resolution signal (typically 0-5V square wave pulses). It expects to receive a consistent stream of pulses at specific frequencies based on engine RPM. When no pulses are detected within a given monitoring window, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CMP B Signal Frequency | Proportional to RPM (pulses per revolution) | Zero pulses detected over monitoring period |
| Signal Voltage | 0-5V square wave pattern | No voltage transitions or constant voltage level |
Code P0739 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, P0739 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.