P0939 Fault Code

Hydraulic Oil Temperature Sensor Circuit Low Input

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0939 fault code indicates a low input signal from the Hydraulic Oil Temperature Sensor Circuit. This sensor is crucial for monitoring the temperature of the hydraulic fluid in the vehicle's transmission system. A malfunction or low input signal may lead to insufficient readings, affecting the vehicle's overall performance.

What are the symptoms of the P0939 code?

When the P0939 code is triggered, symptoms may include:

• Erratic or harsh shifting behavior
• Transmission overheating warnings
• Decreased overall vehicle performance
• Illuminated check engine light
• Potential loss of power to the wheels during driving

What causes the P0939 code?

Several factors can contribute to a P0939 code. Common causes include:

• Faulty hydraulic oil temperature sensor
• Damaged wiring or connectors in the sensor circuit
• Insufficient hydraulic fluid levels
• A malfunctioning or failing transmission control module (TCM)
• Poor grounding or electrical issues within the system

How to fix P0939?

To address a P0939 code, follow these steps:

1. Begin with a thorough visual inspection of the hydraulic oil temperature sensor and its wiring.
2. Check the fluid levels in the transmission and add if necessary.
3. Test the temperature sensor using a multimeter to ensure it provides correct readings.
4. Inspect and repair any damaged wiring or connectors.
5. If issues persist, consider testing or replacing the transmission control module.
6. Clear the fault code and evaluate vehicle performance to ensure the issue is resolved.