P0938 Code: Meaning, Symptoms, Causes & Fix

Overview

Symptoms

• check engine light
• rough operation in certain conditions
• reduced performance

Common causes

• Sensor drift or delayed actuation affecting hydraulic oil temperature sensor range/performance
• Mechanical restriction affecting response
• Connector pin damage/corrosion or harness stress near related components

How to diagnose P0938

1. Confirm P0938 and capture freeze-frame data with a professional scan tool.
2. Inspect wiring, connectors, and grounds related to hydraulic oil temperature sensor range/performance for obvious defects.
3. Compare commanded vs actual values in live data under the same operating condition.
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 P0938

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

Can you drive with P0938?

Most vehicles can be driven short-term with P0938, 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 (performance) in the hydraulic oil temperature sensor range/performance circuit/system.
3. Apply the required relearn/adaptation procedure if specified by service information.
4. Road-test and verify P0938 remains cleared under the conditions that originally set the code.

Fix options

• Test component operation against service specs.
• Replace out-of-range component and verify live data.
• Clear DTCs and verify with live data and completed drive cycle.

Typical repair cost

$200-$900

Common mistakes when diagnosing P0938

• 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.

P0938 in common vehicles

P0938 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 P0938?

P0938 is commonly set by performance faults affecting hydraulic oil temperature sensor range/performance.

How much does it cost to fix P0938?

For P0938, repair costs are typically $200-$900 depending on exact root cause, labor rates, and part quality.

Can I clear P0938 without repair?

You can clear P0938 temporarily, but the code usually returns until the underlying fault is corrected.

Helpful tools

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