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P0940 Generic (SAE) Basic entry

Hydraulic Oil Temperature Sensor Circuit High

Updated 2026-10-02 · Transmission

Severity
Medium
Typical repair cost
40 – 350 EUR
System
Powertrain

What it means

P0940 is stored when the engine control module measures a voltage in the Hydraulic Oil Temperature circuit above the expected maximum, typically because the signal wire is shorted to battery voltage or the circuit is open and pulled up internally.

This entry is compiled automatically from the standard definition and typical diagnostic practice for this type of fault. A detailed, reviewed article is in preparation.

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Symptoms

  • Check engine or transmission warning light
  • Harsh, delayed or missing shifts
  • Transmission stuck in one gear (limp mode)
  • Shuddering or slipping under load

Common causes

  1. Damaged, chafed or corroded wiring in the Hydraulic Oil Temperature circuit
  2. Corroded, loose or water-damaged connector terminals
  3. Failed Hydraulic Oil Temperature component (sensor, solenoid or actuator)
  4. Poor ground connection for the module or component
  5. Faulty control module driver (rare, confirm all else first)

How to diagnose

  1. Read freeze frame data and note when the code set (cold start, under load, after rain)
  2. Inspect the Hydraulic Oil Temperature connector for bent pins, corrosion and water; wiggle the harness with the engine running and watch live data
  3. Measure supply voltage and ground at the connector with the key on
  4. Check the signal wire for shorts to ground or battery and for continuity to the control module
  5. Test or substitute the Hydraulic Oil Temperature only after wiring and connectors are confirmed good
  6. Clear the code and complete a drive cycle to confirm the repair

Frequently asked questions

Can I keep driving with P0940?

Usually yes for a short time, but expect reduced performance or higher fuel use. Have it diagnosed within a few days.

Will clearing P0940 fix it?

No. Clearing only erases the stored code; it returns as soon as the monitor runs again unless the cause is repaired.

Related codes

P0938P0939P0941

Nearby codes in this group