P0379
UniversalTiming Reference High Resolution Signal B No Pulses
High SeverityP0379 indicates that the engine's computer (PCM) is not receiving any high-resolution timing reference pulses from a specific sensor, often the crankshaft position sensor or camshaft position sensor (Signal B). This lack of signal prevents the PCM from accurately determining engine position, which can lead to the engine failing to start or stalling while running.
⚠️ Before You Begin (Safety First)
Always ensure the vehicle is on a level surface and securely chocked before working underneath. Allow the engine to cool before touching any components to prevent burns. Disconnect the battery before performing any electrical work or replacing sensors to avoid accidental short circuits or injury.
Common Symptoms
- Engine cranks but does not start
- Engine stalls unexpectedly while driving
- Rough running or misfires
- Check Engine Light (CEL) illuminated
- No spark or no fuel injector pulse
Common Causes
- Faulty crankshaft position sensor (Signal B)
- Faulty camshaft position sensor (Signal B)
- Open or short circuit in the sensor's wiring harness
- Corroded or loose electrical connector at the sensor or PCM
- Rarely, a faulty Engine Control Module (ECM) or Powertrain Control Module (PCM)
Frequently reported on: General/Universal
Diagnostic Steps
- Inspect the wiring harness and connectors for the crankshaft and camshaft position sensors for any visible damage, corrosion, or loose connections. Repair as needed.
- Locate and test the resistance of the crankshaft and camshaft position sensors using a multimeter, if specifications are available. Compare readings to manufacturer specifications.
- If the sensor is easily accessible, remove and visually inspect it for any physical damage or debris buildup.
- Replace the suspected faulty crankshaft position sensor or camshaft position sensor (Signal B). Ensure it is correctly installed and secured.
- Clear the DTCs from the PCM and test drive the vehicle to verify the repair.
👨🔧 When to Call a Professional
If you've checked the sensor's wiring and connections and replaced the crankshaft position sensor or camshaft position sensor but the engine still exhibits a no-start condition or the code immediately returns, it's time to consult a professional. There might be a deeper electrical issue within the wiring harness or a rare PCM fault.
Commonly Asked Questions
What is a 'Timing Reference High Resolution Signal B'?
This signal is typically generated by a crankshaft or camshaft position sensor, providing precise information about the engine's rotational speed and position to the computer. 'Signal B' refers to a specific sensor or circuit in a multi-sensor system.
Can I drive with a P0379 code?
No, it is highly unlikely your vehicle will even start or run with a P0379 code, as the engine's computer relies on this signal for essential timing. If it does start, it will likely stall immediately or run extremely poorly.
Is P0379 related to P0335 or P0340?
Yes, P0379 is very similar to P0335 (Crankshaft Position Sensor 'A' Circuit Malfunction) and P0340 (Camshaft Position Sensor Circuit Malfunction). All these codes point to issues with engine position sensors, with P0379 being more specific about the lack of a high-resolution signal from a 'B' circuit.
How can I tell if it's the crankshaft or camshaft sensor?
Often, a scan tool can provide more specific data or separate codes (like P0335 for crankshaft or P0340 for camshaft). You can also inspect and test each sensor individually using a multimeter or oscilloscope if you have one, checking for proper signal output.
After replacing the sensor, the code returned. What now?
If the code returns, the issue might not be the sensor itself but the wiring harness leading to it (open/short circuit), a corroded connector, or, in rare cases, a problem with the Powertrain Control Module (PCM). A thorough electrical diagnostic is needed.