OBD-II Generic Error Code P0940: How to Fix It

Q: Can I drive my car with a P0940 code?

It depends on the situation. If the hydraulic fluid is genuinely overheating, driving should be avoided as it can cause serious and costly transmission damage. If the code is caused by a faulty sensor giving a false reading and the transmission is otherwise operating normally, short trips may be acceptable temporarily. However, it is strongly recommended to diagnose and repair P0940 as soon as possible regardless of the cause.

Q: What causes the P0940 code to appear?

The most common causes are a failed or failing hydraulic oil temperature sensor, damaged or corroded wiring and connectors leading to the sensor, low or degraded transmission fluid, a clogged or failing transmission cooler, or actual overheating of the hydraulic system due to heavy load or towing. In rarer cases, an internal transmission fault or a faulty transmission control module (TCM) can also trigger this code.

Q: How much does it cost to fix a P0940 error code?

If the repair is simply replacing a faulty hydraulic oil temperature sensor, parts typically cost between $20 and $80 and labor ranges from $75 to $150 at a shop, making the total repair $100 to $230. If the issue involves a transmission fluid service, cooler replacement, or more extensive internal repairs, costs can range from $200 to over $1,000. Getting a proper diagnosis first will help you avoid unnecessary repairs.

Q: Is P0940 a serious fault code?

P0940 is rated as medium severity. While it may not immediately disable your vehicle, it should not be ignored. If the hydraulic system is genuinely overheating, continued driving can rapidly degrade transmission fluid and cause permanent internal damage, leading to very expensive repairs or a full transmission replacement.

Q: Will a transmission fluid change fix P0940?

If the code was triggered by overheated or degraded transmission fluid, a full fluid change using the correct manufacturer-specified fluid may resolve the issue. However, if the sensor itself is faulty or there is a wiring problem, a fluid change alone will not fix the code. Always diagnose the root cause before assuming a fluid change is sufficient.

Abstract

The OBD-II error code P0940 indicates that the hydraulic oil temperature sensor is reading abnormally high, meaning the transmission or hydraulic system fluid may be overheating or the sensor itself has failed. This code is commonly triggered in vehicles with continuously variable transmissions (CVT) or automatic transmissions that use hydraulic pressure control systems. If left unaddressed, overheating hydraulic fluid can cause serious transmission damage, so it is important to diagnose and resolve this code promptly.