OBD-II Code P0374 — What It Means & How to Fix It

What Does This Error Mean?

P0374 means the PCM is receiving no pulses at all from the high-resolution timing reference signal A. Unlike P0373 (intermittent), this is a complete signal loss. With no high-resolution timing signal, the PCM cannot accurately calculate engine position, which results in poor performance, misfires, or in some cases, a no-start condition.

Affected Models

Older GM vehicles from the late 1990s through mid-2000s with high-resolution timing systems
Common in GM Vortec V8 trucks — 4.8L, 5.3L, 6.0L, and 8.1L engines
Some older GM V6 vehicles with secondary timing reference systems
Less common on modern vehicles and non-GM platforms
Vehicles that have had distributor or timing component replacement are at higher risk if wrong parts were used

Common Causes

Completely dead high-resolution timing sensor — no output signal at all
Open circuit in the sensor wiring — a broken wire between the sensor and PCM
Missing power supply or missing ground at the sensor — the sensor has no power to operate
Completely severed or disconnected sensor connector
Incorrect tone wheel installed with wrong tooth pattern — PCM cannot interpret the signal as valid

How to Fix It

Check whether the sensor connector is connected. A completely unplugged connector is an obvious and common cause of a no-pulse code, especially after recent work in the engine bay. Verify the connector is fully seated and locked.

It sounds basic, but a disconnected sensor is found more often than you might expect after an oil change, valve cover gasket replacement, or any repair near the timing sensor location.
Check the sensor power supply. With the ignition on, measure voltage on the sensor's power supply pin. It should be the reference voltage your vehicle uses — typically 5V or 12V. A reading of 0V means the power supply circuit is open.

Trace the power supply wire back to its source if you get no voltage. A blown fuse, a failed relay, or a broken wire in the supply circuit will cut power to the sensor entirely.
Check the sensor ground. Measure resistance between the sensor ground pin and a known good chassis ground. It should be near 0 ohms. A high resistance reading means the ground circuit is open or corroded.

Many timing sensor grounds run back to the PCM ground or to a dedicated sensor ground point on the engine block. Corrosion at that ground point can kill the signal for multiple sensors at once.
With power and ground confirmed, measure the signal wire for continuity from the sensor connector to the PCM connector. An open circuit in the signal wire will cause the PCM to see nothing. Repair any broken section of the signal wire.

Wire breaks inside the harness often occur at points where the harness is repeatedly flexed — near engine mounts, at the firewall grommet, or where the harness is routed close to sharp metal edges.
If power, ground, and continuity are all good but no signal is present, replace the sensor. A sensor that produces zero output with correct power and ground has failed internally. Clear all codes after replacement and verify normal operation with a scanner.

After repair, verify the sensor output by watching live data on a scanner while cranking the engine. A working sensor should show a changing signal as soon as the engine starts rotating.

When to Call a Professional

A complete loss of the high-resolution timing signal is a definitive fault rather than an intermittent one. If basic checks — power, ground, and continuity — are in order and the signal is still absent, a lab scope can confirm whether the sensor is outputting anything at all. Diagnosis runs $80-$150. Sensor replacement is typically $30-$100 in parts with straightforward labor.

Frequently Asked Questions

Will P0374 cause a no-start condition?

It can on some vehicles, particularly those where the high-resolution signal is the primary reference for fuel injection timing. On GM Vortec engines, a complete loss of the high-resolution timing signal typically results in a very rough or no-start condition because the PCM cannot synchronize fuel injection. Other vehicles may still start but run very poorly.

Is P0374 the same as a crankshaft sensor failure?

Not exactly — they are different sensors. The high-resolution timing sensor is a secondary signal used on specific engine designs. The crankshaft position sensor (which triggers P0335 or P0336) is the primary engine speed and position sensor. Both are important, but the high-resolution timing sensor is an additional layer of precision found on certain engine families.

How do I know if my car even has a high-resolution timing sensor?

The easiest way is to look up the OBD-II wiring diagram or sensor list for your specific vehicle make, model, and year. P0370 through P0379 codes are most commonly seen on older GM vehicles with the specific high-resolution timing system. If you have a modern vehicle from any manufacturer and you are seeing P0374, confirm the code carefully — it may be manufacturer-specific rather than standard OBD-II.