P0374

Timing Reference High Resolution Signal A No Pulses

P0374 is a generic OBD-II powertrain diagnostic trouble code: Timing Reference High Resolution Signal A No Pulses. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0374
Group
Powertrain
System
Powertrain
Severity
Critical (limp mode / no-start)
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What P0374 means

P0374 — "Timing Reference High Resolution Signal 'A' No Pulses" — is the most severe code in the P037x family and indicates that the PCM has received zero pulses from the high-resolution engine position reference on channel A during an engine cranking or running cycle. The high-resolution signal is essential for cycle-accurate ignition timing, direct injection phasing, and variable cam phaser positioning. With a total signal loss, the PCM has no way to determine crankshaft position with the required precision and will typically default to a fail-safe state that prevents or severely disrupts engine operation.

P0374 almost always results in a hard no-start condition. Unlike P0372 (too few pulses) and P0373 (erratic pulses), where some degraded timing data reaches the PCM, P0374 means the signal line is completely dead — the sensor has failed internally, the wiring has an open circuit or a dead short, the reluctor ring has catastrophically separated from the crank, or the sensor supply voltage is absent. On some platforms the PCM can fall back to a low-resolution signal (from a separate sensor circuit) to allow limited cranking, but fuel and ignition delivery remains blocked or severely retarded until the high-resolution signal is restored.

Because P0374 produces no pulses at all, it is diagnostically straightforward compared to the intermittent variants: if the sensor signal wire shows no activity on an oscilloscope during cranking, the fault path is clearly either the sensor, its power/ground circuit, or the wiring between sensor and PCM. Mechanical causes — a separated or severely damaged tone wheel — must also be ruled out before condemning the sensor.

Common causes

Most-frequently reported root causes when P0374 is logged.

  • 1
    Complete internal failure of the crankshaft or camshaft position sensor — no output from the Hall-effect or magnetic pickup element.
  • 2
    Open circuit (broken wire) in the sensor signal line between the sensor and PCM.
  • 3
    Short to ground on the signal wire pulling the output to zero volts continuously.
  • 4
    Loss of the 5V reference voltage supply to the sensor due to a blown fuse, failed relay, or PCM reference circuit failure.
  • 5
    Broken or missing engine ground strap eliminating the sensor signal reference.
  • 6
    Catastrophically damaged or separated reluctor ring (tone wheel) — no teeth pass the sensor at all.
  • 7
    Severely contaminated sensor tip (heavy metallic debris buildup) completely blocking magnetic field variation.
  • 8
    PCM input circuit failure on the channel A high-resolution signal pin.

Symptoms drivers notice

Hard no-start — engine cranks but will not fire (most common presentation).
Engine stalls immediately after starting and cannot be restarted.
Tachometer reads zero during cranking.
MIL / Check Engine Light illuminates (or may not illuminate if the engine never starts).
Complete absence of ignition spark and/or fuel injection on affected cylinders.
On platforms with low-resolution fallback, very rough cranking with extremely retarded timing and no sustained run.

How to diagnose P0374

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and confirm P0374 is stored; check for concurrent cam sensor codes (P0340/P0345) or crankshaft sensor codes (P0335/P0336) that indicate a broader position sensor system failure.
  2. 2
    Verify the 5V reference voltage and ground are present at the sensor connector with the ignition on — absence of reference voltage indicates a fuse, relay, or PCM supply fault upstream.
  3. 3
    Measure signal circuit continuity from sensor to PCM with the connector unplugged; an open circuit reading confirms a broken wire.
  4. 4
    Use an oscilloscope on the signal wire during cranking — a flat line (no waveform) confirms total signal absence. Compare to a known-good pattern for the platform.
  5. 5
    Remove the sensor and visually inspect the tip for heavy metallic contamination or physical damage; also inspect the reluctor ring for catastrophic damage or separation.
  6. 6
    Verify the reluctor ring is fully seated and all teeth are present — a ring that has slipped or shed teeth produces no usable signal.
  7. 7
    Replace the position sensor if power, ground, and wiring are all confirmed intact and the sensor produces no output during cranking; retest.
  8. 8
    If the fault persists after sensor replacement, inspect the PCM input circuit for damage or moisture intrusion.

Related powertrain codes

Frequently asked questions

Will P0374 always cause a no-start?

In most cases, yes. Without any high-resolution pulses, the PCM cannot establish crank position and will withhold spark and fuel injection. On a small number of platforms there is a limp-home fallback using a low-resolution sensor, but even these systems run very poorly and cannot sustain normal operation.

How do I know if the tone wheel is the problem vs the sensor?

Remove the sensor and inspect the reluctor ring visually. A fully intact ring with all teeth present points to a sensor or wiring failure. A damaged, cracked, or missing section of the ring confirms a mechanical cause. An oscilloscope during cranking will show a flat line for either cause, so the visual inspection is essential to distinguish them.

Can a flat battery cause P0374?

Indirectly. A severely discharged battery may not provide enough voltage for the sensor reference circuit during cranking. If the 5V reference drops below the sensor's minimum operating voltage, no pulses are output. This is why verifying battery and reference voltage is an early step in diagnosing P0374 before condemning the sensor.

Is P0374 the same fault as P0335?

They are related but distinct. P0335 is a broad crankshaft position sensor circuit malfunction code. P0374 specifically targets the high-resolution signal channel and the absence of any pulses, implying a total signal loss rather than a range or circuit fault. On platforms with both a standard CKP and a separate high-resolution reference, the two codes can coexist.

Disabling P0374 in software

RaceTune can permanently disable P0374 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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