P0379 Code: Meaning, Symptoms, Causes & Fix

Overview

Symptoms

• hard start when cold
• rough running or misfire
• engine noise or unstable timing

Common causes

• Signal biased high from short-to-voltage affecting timing reference high resolution signal b no pulses
• Sensor output out of expected upper range
• Connector pin damage/corrosion or harness stress near related components

How to diagnose P0379

1. Confirm P0379 and capture freeze-frame data with a professional scan tool.
2. Inspect wiring, connectors, and grounds related to timing reference high resolution signal b no pulses for obvious defects.
3. Compare live data against expected upper threshold and verify reference voltage.
4. Check for related DTCs to identify the root-cause chain before replacing parts.
5. After repair, clear codes and confirm readiness monitors complete without recurrence.

Severity of code P0379

Moderate: This code is moderate severity: the vehicle may still operate, but fault progression can increase repair cost over time.

Can you drive with P0379?

Most vehicles can be driven short-term with P0379, but postpone heavy load/highway driving until repaired.

If the warning lamp is flashing or drivability/safety is affected, avoid driving and diagnose immediately.

How to fix it (step-by-step)

1. Repair obvious wiring/connector faults first to prevent repeat parts replacement.
2. Address the root fault mode (high) in the timing reference high resolution signal b no pulses circuit/system.
3. Apply the required relearn/adaptation procedure if specified by service information.
4. Road-test and verify P0379 remains cleared under the conditions that originally set the code.

Fix options

• Verify reference voltage and inspect wiring.
• Replace failed sensor if signal remains high.
• Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$300-$1400

Common mistakes when diagnosing P0379

• Replacing parts without verifying voltage, ground, and signal integrity first.
• Ignoring related stored/pending codes that indicate upstream faults.
• Skipping post-repair verification drive cycle and readiness checks.

P0379 in common vehicles

P0379 appears across makes such as Mazda, Subaru, Lexus, Jeep. Failure patterns differ by platform: wiring routes, software calibration, and component supplier revisions can change root cause.

Frequently asked questions

What causes P0379?

P0379 is commonly set by high faults affecting timing reference high resolution signal b no pulses.

How much does it cost to fix P0379?

For P0379, repair costs are typically $300-$1400 depending on exact root cause, labor rates, and part quality.

Can I clear P0379 without repair?

You can clear P0379 temporarily, but the code usually returns until the underlying fault is corrected.

Helpful tools

• Estimate repair cost
• Decode your VIN
• Calculate fuel cost