P0374

Universal

Timing Reference High Resolution Signal A No Pulses

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

The engine control system expected pulses from the high-resolution timing reference signal A but did not detect them. This signal helps the system track engine timing. Depending on the vehicle and how the signal is used, the condition may cause starting, running, or performance problems, but the code alone does not identify a failed part.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the engine stalls, will not restart, or loses power while driving, stop somewhere safe and arrange assistance rather than continuing in traffic. If the vehicle runs normally, drive cautiously and have the issue diagnosed promptly.

Common Symptoms

  • The engine may crank but fail to start if the control system cannot use the timing reference signal.
  • The engine may stall or run irregularly if the signal is intermittent or missing while running.
  • Starting, engine response, or performance may be affected if timing information is unavailable or unreliable.
  • The code may be stored without an obvious symptom, particularly if the condition is intermittent.

Common Causes

  • A fault in the source that generates timing reference signal A may prevent pulses from being produced.
  • Damaged, loose, corroded, or poorly connected wiring or connectors may interrupt the signal.
  • A damaged or obstructed signal target may prevent the source from generating a usable pulse pattern, where applicable.
  • Electrical interference or another circuit fault may disrupt the signal.
  • A control-system 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 starts and runs normally, and note any stalling, rough running, or starting difficulty to help describe the condition.
  2. With the engine off, visually inspect accessible wiring and connectors related to the engine timing reference system for looseness, damage, corrosion, or contamination. Do not disconnect components unless the vehicle-specific instructions allow it.
  3. Use a compatible scan tool to record the code and check for related codes or available engine-speed and timing-reference data. Do not treat scan data alone as proof that a particular part has failed.
  4. If the code returns or the engine has running or starting problems, arrange circuit and signal testing using procedures for the exact vehicle. Avoid probing unidentified terminals or replacing parts based only on the code.

When to Call a Professional

A technician can check scan data and related codes, inspect the signal circuit and connections, and use suitable signal-testing equipment to determine whether pulses are reaching the control system. Diagnosis should distinguish a signal-source problem from wiring, connection, target, or control-system issues. Vehicle-specific service information is needed for test points and procedures.

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Commonly Asked Questions

Does P0374 prove that a timing sensor needs replacement?

No. It describes missing pulses from timing reference signal A. The cause could involve the signal source, its target where applicable, wiring, connections, interference, or the control-system input. Testing is needed before choosing a repair.

Can a vehicle have P0374 without noticeable symptoms?

Yes. An intermittent or stored condition may not produce obvious symptoms at the time of inspection. Starting or running problems can occur if the timing reference signal is unavailable when the engine needs it.

Is it safe to keep driving with P0374?

It depends on how the vehicle behaves. If the engine stalls, loses power, or will not restart, stop in a safe place and arrange assistance. If it runs normally, drive cautiously and have it diagnosed promptly.

What distinguishes a signal-source problem from a wiring problem?

A technician checks whether pulses are generated at the source and whether they reach the control-system input, using vehicle-specific circuit information and suitable signal-testing equipment. The code by itself does not make that distinction.

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