JCB Dump Truck 25 Fault Code: Short Circuit To Battery Voltage Or Open Circuit To Transmission Sump Temperature Sensor Input
Short Circuit To Battery Voltage Or Open Circuit To Transmission Sump Temperature Sensor Input · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 25 means the TCU is seeing a voltage that is too high on the transmission sump temperature sensor input, pointing to a short circuit to battery voltage or an open circuit somewhere in that sensor's wiring.
Medium severity. This is a sensor circuit fault, not a direct mechanical failure, but it means the TCU loses accurate transmission sump temperature readings. That can affect transmission protection logic and shift behavior, so it should be diagnosed promptly rather than ignored.
What does JCB Dump Truck error code 25 mean?
Fault code 25 is set when the transmission control unit (TCU) reads a voltage on the transmission sump temperature sensor input that is too high to be a valid reading. This usually means the signal wire has been shorted to battery voltage, or the circuit is open (broken or disconnected) so the TCU sees an out-of-range voltage instead of a real temperature signal.
The transmission sump temperature sensor tells the TCU how hot the transmission oil is. This data helps protect the transmission from overheating and can influence shift mapping and torque converter lockup behavior. When the TCU cannot trust this input, it may fall back to default assumptions, which is not ideal for long-term transmission health.
This code is about the electrical circuit, not the oil temperature itself. The fix is almost always in the wiring, connectors, or the sensor itself rather than the transmission fluid or cooling system.
Common causes of 25
- Cable running from the TCU to the sump temperature sensor is defective and has come into contact with battery voltage, sending an abnormally high signal to the TCU.
- Cable has lost connection to the TCU, creating an open circuit.
- Temperature sensor itself has an internal defect causing it to send an invalid signal.
- A connector pin in the circuit is contacted to battery voltage or is physically broken.
How to troubleshoot JCB Dump Truck 25: first checks
- Inspect the cable running from the TCU to the transmission sump temperature sensor for chafing, pinching, or contact with other wiring that could cause a short to battery voltage.
- Check all connectors in this circuit for corrosion, bent or broken pins, loose terminals, or pins that may be shorting to another circuit carrying battery voltage.
- Verify the cable has a solid, continuous connection at the TCU end. An open circuit here will also trigger this fault.
- Test the temperature sensor itself for an internal defect if the wiring and connectors check out normal.
How the code clears
No separate clearing step is listed for this code. Once the defective cable, connector, or sensor is repaired or replaced and the circuit reads a valid voltage, the fault should clear on its own or after a normal key cycle.
Frequently asked questions
What does fault code 25 mean on a JCB dump truck?
It means the TCU detected a voltage that is too high on the transmission sump temperature sensor input, which points to a short circuit to battery voltage or an open circuit in that sensor's wiring.
Is fault code 25 safe to keep driving with?
The transmission itself may still function, but the TCU is missing reliable sump temperature data, which can affect transmission protection and shift behavior. It should be diagnosed as soon as practical rather than left unresolved.
What usually causes fault code 25?
JCB lists a defective cable shorted to battery voltage, a cable with no connection to the TCU, an internal defect in the temperature sensor, or a connector pin shorted to battery voltage or broken.
How do I troubleshoot fault code 25?
Start by checking the cable between the TCU and the sensor, then inspect all connectors in that circuit for damage or corrosion, and finally test the temperature sensor itself if the wiring checks out fine.
Does fault code 25 require a TCU reset?
No reset procedure is listed for this code. Repairing the wiring, connector, or sensor should allow the fault to clear normally.
Can a bad connector really cause this fault code?
Yes. A connector pin that is contacted to battery voltage or physically broken is one of the specific causes JCB identifies for this fault.