P0373 – Timing Reference High Resolution Signal “A” Intermittent/Erratic Pulses

P0373 is an OBD-II trouble code that points to a problem with the crankshaft position signal – specifically, the signal is erratic or not steady enough for the engine computer to trust. When this happens, the ECU can’t accurately track crankshaft position, which affects ignition timing and fuel injection. You might notice hard starting, misfires, or the engine stalling. This code can be caused by a bad crankshaft position sensor, wiring issues, or even a damaged tone ring. Addressing it early prevents bigger drivability and engine damage issues.

What Does P0373 Mean?

P0373 stands for “High Resolution Crankshaft Position (CKP) Signal Intermittent/Erratic” or similar wording depending on the manufacturer. In simple terms, the ECU is seeing a crankshaft position signal that cuts in and out, has missing pulses, or doesn’t match what it expects during engine operation.

The crankshaft position sensor reads a toothed wheel (tone ring or reluctor) on the crankshaft and sends a digital signal back to the ECU. The ECU uses this high-resolution signal for precise ignition and injection timing. When the signal is unstable, the ECU sets P0373 and may switch to a backup strategy to keep the engine running.

Quick Reference

• Code: P0373
• Meaning: High-resolution crankshaft position signal intermittent/erratic
• Main areas to check: CKP sensor, wiring/connector, tone ring, ECU
• Severity: Moderate to high – can cause stalling and no-start
• Typical fixes: Replace CKP sensor, repair wiring, clean or replace tone ring

Real-World Example / Field Notes

I’ve seen P0373 pop up most often on higher-mileage vehicles that still start but run rough, especially when hot. One common case was a pickup that would crank a long time, then finally start and stumble. The owner had already thrown spark plugs and coils at it. Scope testing the crankshaft signal showed missing pulses whenever the engine warmed up. Replacing the crankshaft position sensor and cleaning corrosion from the connector solved it immediately. The key lesson: don’t ignore intermittent starting or random stalls when this code is stored.

Symptoms of P0373

• Hard starting – extended cranking time before the engine fires
• Intermittent stalling – engine may die at idle or while driving
• Rough idle – unstable RPM, shaking, or hunting at stoplights
• Engine misfire – hesitation, jerking, or loss of power under load
• Reduced power – ECU may go into a protective or “limp” mode
• Check engine light – MIL illuminated, sometimes with related codes
• Poor fuel economy – incorrect timing leads to higher fuel consumption
• No-start condition – in severe cases, the engine may not start at all

Common Causes of P0373

Most Common Causes

• Faulty crankshaft position (CKP) sensor – internal failure, heat damage, or age causing a weak or erratic signal.
• Damaged or corroded CKP connector – loose pins, moisture intrusion, or green corrosion increasing resistance.
• Wiring issues in CKP circuit – chafed insulation, broken wires, or poor ground causing intermittent signal loss.
• Contaminated sensor tip – metal shavings, oil sludge, or debris on the sensor face interfering with signal.
• Improper sensor air gap – sensor not seated fully or wrong sensor type, changing the distance to the tone ring.

Less Common Causes

• Damaged tone ring/reluctor wheel – missing teeth, bent wheel, or cracks causing irregular pulses.
• Aftermarket performance parts – lightweight flywheels or crank pulleys with different tooth patterns.
• ECU/PCM internal fault – rare, but possible if all other components test good.
• Poor engine grounds – corroded or loose ground straps affecting sensor reference and signal quality.
• Previous engine work – incorrectly installed timing components or sensor bracket misalignment.

Diagnosis: Step-by-Step Guide

You’ll want a basic tool set plus a quality scan tool (preferably with live data), a digital multimeter, and ideally an oscilloscope for viewing the crankshaft signal. A service manual or wiring diagram for your specific vehicle is also very helpful.

1. Confirm the code and check for companions. Use a scan tool to read all stored and pending codes. Note any related CKP, CMP (camshaft), or misfire codes. Clear the codes and see if P0373 returns quickly.
2. Review live data. With the engine cranking or running, look at engine RPM and CKP signal status. If RPM drops to zero while cranking or during a stall, the ECU is losing the crank signal.
3. Perform a visual inspection. Locate the crankshaft position sensor and inspect the harness. Look for oil-soaked connectors, broken clips, rubbed-through insulation, or wires too close to ignition coils or plug wires (which can induce noise).
4. Check connector and terminals. Unplug the CKP sensor and inspect the pins for corrosion, bent terminals, or moisture. Gently tug on each wire to catch hidden breaks near the connector.
5. Test sensor resistance and power/ground. With a multimeter, measure CKP sensor resistance (for 2-wire magnetic types) and compare to specs. On 3-wire Hall-effect sensors, verify you have proper 5V reference, ground, and signal voltage at the connector.
6. Scope the CKP signal if possible. Using an oscilloscope, monitor the CKP signal while cranking and idling. Look for clean, evenly spaced pulses. Missing or distorted pulses, especially when you wiggle the harness, point to sensor or wiring faults.
7. Inspect the tone ring/reluctor. If accessible, remove the sensor and inspect the tone ring with a light. Look for missing teeth, cracks, heavy rust, or metal debris. On some engines, you may need to remove covers or even the transmission to fully inspect.
8. Check sensor mounting and air gap. Make sure the sensor is seated fully and bolted correctly. Compare the air gap (distance to tone ring) to factory specs. A loose or misaligned sensor can cause intermittent readings.
9. Use Mode $06 (if available). Some scan tools can access Mode $06 data to show misfire or CKP-related test results. This can help confirm a borderline sensor that hasn’t completely failed.
10. Rule out ECU issues last. Only after confirming good power, grounds, wiring, sensor, and tone ring should you suspect the ECU. Check for TSBs (technical service bulletins) about software updates or known CKP signal issues.

Pro tip: If the code sets more often when the engine is hot, use a heat gun or hair dryer to warm the CKP sensor and harness during testing. Many crank sensors fail only when heat-soaked, making them tricky to catch when cold.

Possible Fixes & Repair Costs

Most P0373 repairs involve replacing the crankshaft position sensor or repairing wiring. Typical repair costs vary widely by vehicle and access. Expect roughly $75–$200 for a CKP sensor part, plus 0.5–2.0 hours of labor, putting you in the $150–$450 range at most shops. Wiring repairs can be $100–$300 depending on how deep the damage is. If the tone ring or reluctor wheel is damaged and requires transmission or timing cover removal, costs can jump into the $500–$1,200 range. ECU replacement or reprogramming, while rare, may run $600–$1,500.

Can I Still Drive With P0373?

Sometimes you can, but you shouldn’t rely on it. With P0373, the engine computer may still run the engine using backup strategies, but the crank signal can drop out unexpectedly. That means the engine might stall without warning, hesitate during passing, or fail to restart after you stop for fuel. Short, careful trips to a repair shop are usually fine, but long-distance driving or heavy traffic is risky. Treat this as a “fix soon” issue, not something to ignore for weeks.

What Happens If You Ignore P0373?

If you ignore P0373, the intermittent crank signal can lead to more frequent stalling, hard starting, and potential no-start situations, leaving you stranded. Over time, incorrect ignition timing can increase stress on the engine and catalytic converter due to misfires and unburned fuel. In severe cases, repeated stalling in traffic can become a safety concern. Fixing the root cause early is cheaper and safer than waiting until the vehicle won’t start at all.

Last updated: February 13, 2026

Vehicles Commonly Affected by P0373

P0373 can show up on many OBD-II vehicles, but it’s more common on certain platforms. You’ll often see it on GM trucks and SUVs (Chevrolet Silverado, GMC Sierra, Tahoe, Suburban), various Ford models (F-150, Explorer, Mustang), and some Chrysler/Dodge/Jeep vehicles with V6 and V8 engines. It also appears on select Volkswagen/Audi, BMW, and Toyota models that use high-resolution crank sensors. High-mileage engines, vehicles with prior engine or transmission work, and those driven in harsh climates tend to be more prone to this code.