JCB Dump Truck 27 Fault Code: Short Circuit To Battery Voltage Or Open Circuit At Converter Output Temperature Sensor Input
Short Circuit To Battery Voltage Or Open Circuit At Converter Output Temperature Sensor Input · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Fault code 27 means the JCB dump truck's control system has measured a voltage that is too high on the converter output temperature sensor input. This points to a short to battery voltage or an open circuit in the wiring, connector, or sensor for the torque converter output temperature signal.
Medium severity. This is a sensor circuit fault, not an immediate mechanical failure. However, losing accurate converter output temperature readings means overheating conditions in the transmission or converter could go undetected. Diagnose promptly rather than ignoring it, especially before sustained heavy hauling.
What does JCB Dump Truck error code 27 mean?
Fault code 27 is set when the TCU (transmission control unit) sees a measured voltage that is too high on the input circuit for the converter output temperature sensor. Instead of reading a normal temperature signal, the control system sees a voltage pattern consistent with either a short to battery voltage or a broken, disconnected circuit.
This sensor tells the TCU how hot the fluid is coming out of the torque converter. That is an important number for protecting the transmission and converter from heat damage. When the signal circuit fails electrically, the TCU can no longer trust the reading, so it flags this fault to alert the operator and technician.
This code is purely about the electrical circuit and sensor, not a confirmed high temperature condition in the converter itself. The truck may still be running normally, but the temperature monitoring for that circuit is compromised until the fault is fixed.
Common causes of 27
- A cable in the sensor circuit is defective and has come into contact with battery voltage, causing the TCU to see an abnormally high signal.
- The cable has no connection to the TCU, creating an open circuit condition.
- The temperature sensor itself has an internal defect.
- A connector pin in the circuit is contacted to battery voltage or is physically broken.
How to troubleshoot JCB Dump Truck 27: first checks
- Inspect the cable running from the TCU to the converter output temperature sensor for chafing, pinching, or damaged insulation that could allow contact with battery voltage.
- Check all connectors in this circuit for corrosion, loose pins, moisture intrusion, or broken pins, and confirm each connector is fully seated.
- Test the temperature sensor itself for an internal defect using appropriate electrical testing methods.
- Verify continuity of the cable between the TCU and the sensor to rule out an open circuit or lost connection at the TCU end.
How the code clears
No separate clearing step is listed for this code. Once the cable, connector, and sensor have been inspected and repaired as needed, the fault should stop being set on its own as the circuit returns to a normal voltage range. No reset procedure is listed for this code.
Frequently asked questions
What does JCB fault code 27 mean on a dump truck?
It means the TCU has detected a measured voltage that is too high on the converter output temperature sensor input circuit. This is caused by either a short to battery voltage or an open circuit in the wiring, connector, or sensor itself.
Is it safe to keep driving with fault code 27 active?
The truck may still operate, but the TCU is no longer getting a reliable converter output temperature reading. Since this reading helps protect the transmission and converter from overheating, it is best to diagnose the fault before extended or heavy-duty operation.
What usually causes this fault code?
JCB lists four possible causes: a defective cable shorted to battery voltage, a cable with no connection to the TCU, an internal defect in the temperature sensor itself, or a connector pin that is contacted to battery voltage or broken.
How do I start diagnosing fault code 27?
Start by checking the cable between the TCU and the sensor for damage, inspecting all connectors for corrosion or broken pins, and testing the sensor for an internal defect. These are the three checks JCB specifies for this fault.
Will fixing the wiring clear the code automatically?
No separate clearing or reset procedure is listed for this fault. Once the underlying cable, connector, or sensor issue is repaired, the abnormal voltage condition should go away and the fault should not reset.
Does fault code 27 mean the transmission is overheating right now?
Not necessarily. This code is about a fault in the electrical sensor circuit itself, not a confirmed high temperature reading. It means the TCU cannot trust the signal it is getting, not that the converter is definitely overheating.