OBD-II Code P0376 — What It Means & How to Fix It

What Does This Error Mean?

P0376 means the PCM is counting more timing pulses from high-resolution reference signal B than it expects in one crankshaft revolution. Extra pulses corrupt the PCM's engine position calculation, causing timing errors in fuel injection and ignition. Expect rough running, hesitation, misfires, and reduced efficiency.

Affected Models

Older GM vehicles with dual high-resolution timing reference sensors
Common in GM Vortec V8 trucks and SUVs from the late 1990s to mid-2000s
Some GM performance vehicles with the LS engine family
Less common on modern vehicles and non-GM platforms
More frequently seen on vehicles that have had distributor or reluctor ring work done

Common Causes

Damaged or chipped tone wheel for sensor B creating an extra pulse per revolution
Metal debris or ferrous particles on the sensor B reluctor ring generating phantom pulses
Wrong reluctor ring installed during a previous repair — incorrect tooth count for sensor B
Sensor B mounted too close to the tone wheel, picking up magnetic bounce signals
Electrical interference from ignition wires or other sources inducing false pulses on the signal wire

How to Fix It

Locate the tone wheel that high-resolution timing sensor B reads. Remove the sensor and inspect the reluctor ring carefully for chipped, cracked, or broken teeth. Any tooth irregularity will generate an extra pulse at the exact point in the revolution where the damage occurred.

Inspect under good lighting. Run a finger around the entire ring to feel for irregularities. A small chip that looks minor can still generate a detectable phantom pulse.
Clean the tone wheel of any metal debris, oil residue, or ferrous material. Debris attracted to the magnetic sensor or lodged between teeth can mimic extra teeth. Use brake cleaner and a clean lint-free cloth.

After cleaning, inspect again carefully. If the source of extra pulses was contamination rather than a damaged tooth, a thorough cleaning may resolve the code without part replacement.
Verify the sensor B air gap. A sensor mounted too close to the tone wheel can pick up the trailing edge of a tooth as a separate pulse — effectively doubling some pulses. Measure the gap with a feeler gauge and adjust to specification.

The air gap spec is typically 0.5 to 1.5 mm. Check both the initial gap and whether the sensor can shift in its bore. A loose mounting bolt allows the sensor to vibrate closer to the wheel at certain RPM.
If this vehicle has had recent distributor or timing component replacement, verify the correct reluctor ring was installed for your specific engine. A ring with more teeth than the original creates a constant P0376 on every drive cycle.

Part number verification is important here. Reluctor rings are not universal — they are specific to the engine, model year, and timing system variant. Even a ring that fits mechanically may have the wrong tooth count.
Check the routing of the sensor B signal wire. If it runs parallel and close to spark plug wires or ignition coil wires for a significant distance, electromagnetic interference can induce phantom pulses. Reroute the signal wire away from ignition components.

On older GM vehicles with high-voltage conventional spark plug wires, routing the timing sensor harness near those wires is a known cause of induced interference pulses.

When to Call a Professional

Too-many-pulses codes typically involve a damaged tone wheel or an incorrect sensor gap. A lab scope will show the actual pulse pattern and immediately reveal whether there is an extra tooth or electrical noise in the signal. Diagnosis runs $80-$150. Tone wheel replacement cost depends on location — from $50 to several hundred dollars including labor if significant disassembly is needed.

Frequently Asked Questions

How does the PCM detect that there are too many pulses?

The PCM knows the exact number of pulses it should receive from sensor B for each full crankshaft revolution based on the tooth count on the reluctor ring. It counts incoming pulses and compares that count to the expected number. If it counts more pulses than expected before the crankshaft completes a full turn, it stores P0376. Even one extra pulse per revolution is enough to trigger this code over time.

Can a P0376 be caused by driving on rough roads?

Indirectly yes. Vibration from rough roads can cause loose metal particles in the engine oil to travel to the reluctor ring area and collect near the sensor. It can also loosen the sensor mounting bolt, changing the air gap. If you recently drove on very rough terrain and then noticed this code, checking for debris and verifying the sensor mounting is a good first step.

Is P0376 the B version of P0371?

Yes, exactly. P0371 is a too-many-pulses fault for high-resolution timing signal A. P0376 is the same fault type for signal B. The diagnosis and repair steps are essentially identical — you are dealing with the same type of problem on a second sensor and reluctor ring on the same engine.