What is P0840 fault code and what does it mean? What is the description of Transmission Oil Pressure Sensor/Switch “A” Circuit Malfunction? How can you fix the fault code P0840? What are the causes and symptoms of the P0840 fault?
What is the P0840 fault code? What does it all mean?
The P0840 code means that the voltage signal from “A” the transmission oil pressure sensor circuit is not in compliance with manufacturer specifications.
The transmission control module (TCM), or powertrain control module, uses the oil pressure sensor to monitor the hydraulic pressure while shifting. The oil pressure sensor is typically located near the hydraulic control unit (valve-body / transmission computer) within the transmission. In some cases, it may be mounted near the transmission case.
The transmission oil pressure sensor converts mechanical oil pressure into an electric signal. The voltage signal of the sensor will increase if the oil pressure is higher, and vice versa. This information is sent to the PCM/TCM in order to monitor the transmission operating temperature and perform the shifting process. The P0840 code is triggered if there is a discrepancy between the voltage signal from sensor and the expected voltage signal by the PCM. To identify the “A” circuit in your vehicle, consult specific repair manuals.
Problems with the electrical circuit of a sensor are usually responsible for P0840. But, setting the code could result in transmission oil leaking, cracks in the hydraulic computer or low system operating tension. This can also be caused mechanical problems.
What is the P0840 Fault Code?
Below are some reasons to set fault code P0840:
- – Broken, damaged, melted, or broken wires, loose connectors and open circuits
- – Defective electronic pressure control solenoid
- – Sensor for oil pressure in transmissions that is defective
- – Blockage of transmission fluid passage lines
- – Transmission internal mechanical problems
- – Transmission oil missing, dirty, or contaminated
- – Defective transmission high press pump
- – Leakage of transmission oil from components or gaskets
- – Defective torque converter clutch connection
- – Defective PCM / TCM (rarely)
What are the symptoms for the P0840 fault code?
You may experience the following symptoms if your vehicle has the code P0840:
- – Illumination for check engine light
- Transmission warning lamp is now available
- – Transm oil heated to high temperatures
- – Oily odors emanating from the gearbox
- – Smoke coming off the gearbox
- – Difficulty changing gears
- – Gearbox slip
- Transmission oil leaks
- – Torque converter clutch not engaging or disengaging
- – The PCM can go into safe mode and lock the vehicle in 2nd, or 3rd gear
How to Fix the P0840 Fault Code
The following repairs may be able to resolve the P0840 fault code:
- – Replacing a defective electronic pressure control solenoid
- – How to replace a damaged pressure sensor for transmission oil
- – Cleansing clogged transmission fluid passagelines
- – Repair of mechanical transmission failures
- – Clean the filter and replace the oil in the gearbox.
- – Filling in the gaps with transmission oil
- Repair of damaged cables and connectors, as well as open or short circuits
- – Replacing a defective transmission high-pressure pump
- Repair of transmission oil leaking
- – Test and replacement of PCM and TCM
How serious is the P0840 Fault code?
P0840, one of the most serious codes, should be fixed immediately. You can’t tell whether the fault is an electrical problem, a defective sensor, or a fault in the transmission. You may experience severe drivability issues in any of these cases. You could cause the complete failure of your gearbox if you don’t intervene quickly. Leakages can cause the transmission oil to dry out completely. This code should not to be taken lightly as it could lead to high repair costs.
