What Does P0938 Mean?
DTC P0938 indicates that the hydraulic oil temperature sensor is reporting values outside the expected range or the readings do not correlate with operating conditions. For example, the sensor may show no temperature change after extended driving, or the reported temperature may be erratic without corresponding to actual fluid temperature changes. This is a rationality check failure rather than a hard circuit fault.
Common Causes
30%
Hydraulic oil temperature sensor degraded or drifting out of calibration
20%
Sensor mounted incorrectly or not making proper thermal contact with fluid
20%
High-resistance connection at the sensor connector causing skewed readings
20%
Actual hydraulic system thermal issue (stuck thermostat, plugged cooler)
10%
TCM software calibration error or mismatched sensor specification
Diagnostic Steps
1
Step 1: Using a scan tool, monitor the hydraulic oil temperature reading during a cold start and warm-up. Compare the initial reading to ambient temperature and verify it rises steadily during operation.
2
Step 2: Compare the hydraulic oil temperature sensor reading to engine coolant temperature. After extended driving, they should be within a similar range (transmission fluid is typically 20-40F higher than coolant).
3
Step 3: Inspect the sensor connector for corroded or high-resistance terminals that could skew the resistance reading. Clean contacts and verify tight pin fit.
4
Step 4: Remove the sensor and test its resistance at known temperatures using a multimeter and a temperature-controlled environment. Verify it matches the manufacturer's specification curve.
5
Step 5: If the sensor tests good, investigate the hydraulic cooling system for restrictions: check the transmission cooler for blockage, inspect cooler lines for kinks, and verify thermostat operation if equipped.
Estimated Repair Cost
$120 - $450
Parts + labor, varies by vehicle and location
DTC P0938 indicates that the hydraulic oil temperature sensor is reporting values outside the expected range or the readings do not correlate with operating conditions. For example, the sensor may show no temperature change after extended driving, or the reported temperature may be erratic without c...
The most common cause of P0938 (Hydraulic Oil Temperature Sensor Range/Performance) is: Hydraulic oil temperature sensor degraded or drifting out of calibration
Typical repair costs for P0938 range from $120 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Range/performance issues with the temperature sensor typically do not cause immediate safety concerns but can lead to suboptimal shift adaptation, reduced transmission longevity, and potential overheating if the underlying issue is a cooling system problem.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0938 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission / Clutch Hydraulic System
Difficulty
Type
Generic (SAE)
Recommended Tools
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