P0373

Universal

Timing Reference High Resolution Signal A Intermittent/Erratic Pulses

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The engine control system monitors a high-resolution timing reference signal to track engine position and timing. This code means signal A is being detected inconsistently or with erratic pulses. Depending on the vehicle, that can affect starting or engine operation, but the code alone does not prove that a particular sensor or part has failed.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the engine stalls, loses power, or runs severely rough, pull over safely and avoid continuing to drive; unexpected stalling can create a traffic hazard. If the vehicle runs normally, arrange diagnosis soon and watch for worsening symptoms.

Common Symptoms

  • The engine may crank longer than usual or be difficult to start if the timing reference signal is unreliable during cranking.
  • The engine may stumble, misfire, run roughly, or hesitate if inconsistent timing information disrupts engine control.
  • The engine may stall intermittently if the signal drops out while running.
  • The fault may come and go, and the vehicle may show no noticeable symptoms when the signal is behaving normally.

Common Causes

  • An intermittent connection, damaged wire, or poor terminal contact in the timing reference signal circuit can interrupt pulses.
  • A sensor or other signal source may produce an inconsistent output, depending on the vehicle's design.
  • A damaged, loose, or contaminated signal target or related mechanical component may disturb pulse generation.
  • Electrical interference or an issue with circuit power or ground, where applicable, may make the signal erratic.
  • A control-module input fault is possible but should be considered only after the signal source and circuit have been checked.

Diagnostic Steps

  1. Check whether the engine is stalling, running roughly, or difficult to start. Stop driving if it stalls or loses power in a way that makes continued travel unsafe.
  2. With the engine off, visually inspect accessible timing-reference sensor wiring and connectors for damage, loose connections, corrosion, or signs of rubbing. Do not pull on wires or disturb hot or moving parts.
  3. Record any other diagnostic codes and note when the symptoms occur, such as during starting or while driving. Related codes and conditions can help guide diagnosis.
  4. If you have a suitable scan tool, check for relevant live engine-speed or timing data during cranking and operation, following the tool and vehicle instructions. Inconsistent readings can support further circuit diagnosis but do not identify a failed part by themselves.
  5. If visual checks do not reveal a problem, have the signal circuit and waveform tested using vehicle-specific service information. Avoid probing unknown terminals or replacing parts based only on this code.

When to Call a Professional

A technician can inspect the signal circuit and connectors, check power and grounds where applicable, and compare the timing-reference waveform with scan data during the conditions that reproduce the fault. A scope may help identify intermittent signal dropouts. Check the sensor, signal target, wiring, and control-module inputs before deciding what to replace; procedures and expected signals vary by vehicle.

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Commonly Asked Questions

Does P0373 prove that the timing sensor has failed?

No. It reports an intermittent or erratic timing-reference signal. Wiring, connections, the signal target, power or ground issues, and the control-module input may also need to be checked.

Can I keep driving with P0373?

That depends on how the engine behaves. If it stalls, loses power, or runs severely rough, stop when safe and do not continue driving. If there are no symptoms, arrange diagnosis soon because the condition may return.

Why might the code appear intermittently?

A loose or damaged connection, a signal source that drops out under certain conditions, or an issue affecting the signal target can cause pulses to become inconsistent. Testing during the conditions that reproduce the fault is useful.

What test can help distinguish a sensor issue from a wiring problem?

A technician can inspect the circuit and compare the signal waveform at appropriate points using vehicle-specific procedures. This can help locate where the signal becomes erratic; the code alone cannot make that distinction.

Can a vehicle have this code without noticeable symptoms?

Yes. An intermittent fault may not affect how the vehicle runs every time. Symptoms can appear later or only under particular operating conditions.

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