P0379 – Timing Reference High Resolution Signal “B” No Pulses

P0379 is one of those ignition-related trouble codes that can be confusing because it sounds very technical, but it usually comes down to a simple issue: the engine computer is not happy with a signal from a timing or reference sensor. When this code sets, your ECU is seeing an intermittent or incorrect high-reference signal that it uses for spark timing and fuel control. In plain terms, the computer is losing track of engine position. That can lead to hard starts, misfires, and poor drivability if you don’t track it down.

What Does P0379 Mean?

P0379 is defined as “High Resolution B Signal – Intermittent/Erratic” or “Timing Reference High Resolution B Circuit Intermittent,” depending on the manufacturer. It usually refers to a secondary high-resolution signal from a crankshaft or camshaft position system that the ECU uses to fine-tune ignition timing and injection events.

When the ECU detects that this “B” reference signal is missing, erratic, or out of range for a certain period, it stores P0379 and often turns on the check engine light. The engine may still run, but the computer may fall back to a less precise strategy, which you’ll feel as roughness or hesitation.

Quick Reference

• Code: P0379 – High Resolution B Signal / Timing Reference B Circuit Intermittent
• System: Ignition / Engine timing reference
• Typical causes: Faulty crank/cam sensor, wiring issues, poor connections, damaged reluctor wheel
• Severity: Moderate – can lead to stalling and hard starting if ignored
• Common fixes: Sensor replacement, wiring repair, connector cleaning, reluctor inspection

Real-World Example / Field Notes

In the shop, I usually see P0379 on higher-mileage vehicles that have had some previous engine work, or on cars that live in harsh climates. One case that stands out was a V6 sedan that came in with intermittent stalling and a random misfire. The scan tool showed P0379 along with a few misfire counters in Mode $06. The crank sensor had already been replaced by another shop, but the problem remained. After some digging, I found a corroded connector pin and a cracked wire right at the sensor harness. A simple wiring repair and connector cleaning completely cured the issue. That’s a good reminder: don’t just throw sensors at a timing code—always inspect the wiring and connectors carefully.

Symptoms of P0379

• Check engine light on: P0379 usually sets a MIL, sometimes with other ignition or misfire codes.
• Hard starting: The engine may crank longer than normal or require multiple attempts to start.
• Rough idle: Unstable idle speed, shaking, or occasional stumble as timing control degrades.
• Engine hesitation: Noticeable lag or stumble when accelerating, especially from a stop.
• Intermittent stalling: Engine may die at idle or when coming to a stop if the reference signal cuts out.
• Reduced power: ECU may use a backup strategy, causing sluggish performance and poor throttle response.
• Poor fuel economy: Inaccurate timing can lead to increased fuel consumption over time.
• Occasional misfires: You may feel light misfires or surging, especially under load.

Common Causes of P0379

Most Common Causes

• Faulty crankshaft or camshaft position sensor (high-res “B”): Internal failure, heat damage, or contamination in the sensor can cause an intermittent signal.
• Damaged wiring to the sensor: Chafed, pinched, or broken wires near the engine or transmission bellhousing are very common, especially after engine or clutch work.
• Corroded or loose electrical connectors: Moisture intrusion, oil saturation, or loose pins at the sensor or ECU connector can cause erratic voltage readings.
• Improper sensor air gap: On some systems, the distance between the sensor and reluctor wheel is critical; incorrect installation or missing shims can create an intermittent signal.
• Failed aftermarket sensor: Cheap replacement sensors often don’t produce a clean enough signal for the ECU, leading to repeat P0379 codes.

Less Common Causes

• Damaged reluctor wheel / tone ring: Bent teeth, missing segments, or debris on the crank or cam reluctor can distort the high-resolution signal.
• ECU (PCM) internal fault: Rare, but a failing driver circuit or internal reference circuit can misread an otherwise good signal.
• Improper engine timing or mechanical damage: Jumped timing chain/belt or excessive crankshaft end play can cause inconsistent sensor readings.
• Poor engine ground or power supply issues: Weak grounds or voltage drops can affect sensor reference voltage and signal quality.
• Aftermarket performance modifications: Lightweight flywheels, custom crank triggers, or poorly calibrated engine management can trigger P0379 on some platforms.

Diagnosis: Step-by-Step Guide

To properly diagnose P0379, you’ll want a quality scan tool (ideally with live data and Mode $06), a digital multimeter, basic hand tools, and access to wiring diagrams or service information for your specific vehicle. An oscilloscope is ideal for viewing the sensor waveform, but not mandatory for basic checks.

1. Confirm the code and check for companions. Scan for all stored and pending DTCs. Note any crank/cam, misfire, or power supply codes that may be related. Clear the codes and see if P0379 returns quickly or only under certain conditions (heat, RPM, bumps).
2. Visual inspection of sensor and wiring. Locate the high-resolution “B” sensor (often a crank or secondary cam sensor). Inspect the harness for rubbing, oil saturation, melted insulation, or obvious damage. Check the connector for corrosion, bent pins, or loose locking tabs.
3. Check sensor power and ground. With a multimeter, verify that the sensor has proper reference voltage (often 5V) and a good ground at the connector. Wiggle the harness lightly while monitoring voltage to catch intermittent drops.
4. Inspect the reluctor wheel or tone ring. If accessible, look for missing teeth, cracks, metal shavings, or heavy rust on the crank or cam reluctor. On some engines, you may need to remove a cover or use a borescope through an inspection hole.
5. Monitor live data. Use your scan tool to watch crank and cam sync, RPM, and any “high-resolution” signal parameters while cranking and running. Look for dropouts, sudden RPM spikes, or loss of sync when the problem occurs.
6. Perform a wiggle test. With the engine idling, gently move the harness and connector for the sensor and along the route to the ECU. If the engine stumbles or the live data glitches when you move a certain section, you’ve likely found a wiring fault.
7. Test the sensor resistance and output. With the sensor unplugged, measure resistance against spec. Some sensors can also be tested for AC voltage output while cranking. Compare your readings to service manual values.
8. Check Mode $06 data (if available). Some vehicles store misfire and crank/cam signal quality data in Mode $06. Look for any test results just on the edge of failing, which can point to a marginal sensor or wiring issue.
9. Substitute a known-good sensor (if justified). If wiring, power, and ground check out and the reluctor looks good, replacing the suspect sensor with a quality OEM or OE-equivalent part is often the next logical step.
10. Consider ECU testing or reflash (last resort). Only after all other checks pass and the issue persists should you suspect an ECU problem. At that point, professional-level diagnostics or ECU testing is recommended.

Pro tip: When replacing a crank or cam sensor for P0379, always clean the mounting surface, verify the correct air gap (if adjustable), and route the harness away from ignition coils and high-current wiring to avoid electrical interference.

Possible Fixes & Repair Costs

Repairs for P0379 usually focus on restoring a clean, stable timing reference signal to the ECU. In many cases, this means replacing a failing crank or cam sensor or repairing damaged wiring. Typical repair costs vary by vehicle, labor rates, and how buried the sensor is. A basic sensor replacement might run $100–$300 parts and labor, while more complex jobs that require significant disassembly or reluctor inspection can climb to $400–$700. Wiring repairs can range from a simple $80–$150 fix to several hundred dollars if a harness section needs to be replaced. ECU-related repairs or timing component work are on the high end and can exceed $1,000 depending on the make and model.

Can I Still Drive With P0379?

In many cases, you can still drive with P0379 for a short period, but it’s not something you want to ignore. If the ECU can still get a usable signal, it will often default to a backup strategy, so the engine runs but not perfectly. You may notice rough idle, hesitation, or occasional stalling. If the signal fails completely, the engine may not start or could stall unexpectedly, which is a safety concern. If the car runs poorly or stalls, have it towed rather than risk being stranded or causing an accident.

What Happens If You Ignore P0379?

Ignoring P0379 can lead to increasingly unstable engine operation, more frequent stalling, and potential no-start situations. Over time, misfires and poor combustion can damage the catalytic converter and other components, turning a relatively simple sensor or wiring repair into a much more expensive problem.

Last updated: February 13, 2026

Vehicles Commonly Affected by P0379

P0379 can show up on many OBD-II vehicles, but it’s more frequently seen on certain platforms that rely heavily on high-resolution crank and cam signals. You’ll often find this code on GM vehicles (Chevrolet, GMC, Buick, Cadillac) with V6 and V8 engines, as well as some Ford, Chrysler, and Dodge models. It can also appear on European brands like BMW, Mercedes-Benz, and Volkswagen that use complex timing reference systems, and on some Japanese vehicles such as Honda, Toyota, and Nissan with advanced ignition control. High-mileage cars, trucks, and SUVs that have seen engine work or harsh environments are especially prone.