P0843 Transmission Fluid Pressure Sensor / Switch A Circuit High
OBD-II Trouble Code Technical Description
Transmission Fluid Pressure Sensor / Switch "A" Circuit High
What does that mean?
This generic powertrain/engine diagnostic trouble code typically applies to all OBD-II equipped vehicles including but not limited to Dodge, Chrysler, Chevrolet, GMC, Acura, Toyota, etc. but seems to be most commonly seen on Honda vehicles.
The Transmission Fluid Pressure Sensor/Switch (TFPS) is usually found attached to the side of the valve body inside the transmission, although sometimes it may be found screwed into the side of the transmission case/body itself.
The TFPS converts the mechanical transmission pressures into an electrical signal for the Powertrain Control Module (PCM) or Transmission Control Module (TCM). Typically, the PCM/TCM will then inform other controllers utilizing the vehicle's data communication bus.
The PCM/TCM receives this voltage signal to determine transmission operating pressure or when a shift is occurring. This code is set if this "A" input does not match normal operating voltages stored in the PCM/TCM's memory. Refer to a vehicle specific repair manual to determine which is the "A" circuit for your particular vehicle.
P0843 is typically an electrical circuit (TFPS sensor circuit) issue. This cannot be overlooked in the troubleshooting stage, especially when dealing with an intermittent problem.
Troubleshooting steps may vary depending upon manufacturer, type of TFPS sensor and wire colors.
Related trans fluid pressure sensor A circuit codes:
P0840 Transmission Fluid Pressure Sensor/Switch "A" Circuit P0841 Transmission Fluid Pressure Sensor/Switch "A" Circuit Range/Performance P0842 Transmission Fluid Pressure Sensor/Switch "A" Circuit Low P0844 Transmission Fluid Pressure Sensor/Switch "A" Circuit IntermittentCode Severity & Symptoms
Severity depends upon which circuit the failure has occurred in. Since this is an electrical failure, the PCM/TCM can compensate to some degree. The failure may mean that the PCM/TCM modifies the shifting of the transmission if electronically controlled.
Symptoms of a P0843 engine code may include:
Malfunction Indicator Light On Change in shift quality Vehicle starts off in 2nd or 3rd gear (limp in mode)Causes
Typically the causes for this code to set are:
Short to power in the signal circuit to the TFPS sensor - possible Open on ground circuit to the TFPS sensor - possible Failed TFPS Sensor / internally shorted - likely Failed PCM - unlikely (programming required after replacement)Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
A good example of this would be if there are any known power related codes set along with the P0843, or if there is more than one pressure sensor/switch code set. If so, begin your diagnosis with the power related fault code first, or with the multiple code diagnosis first, as this may be the reason for the P0843.
Next, locate the Transmission Fluid Pressure Sensor/Switch (TFPS) on your particular vehicle. The TFPS is usually found attached to the side of the valve body inside the transmission, although sometimes it may be found screwed into the side of the transmission case/body itself. Once located, visually inspect the connector and wiring. Look for scraping, rubbing, bare wires, burn spots or melted plastic. Pull the connector apart and carefully inspect the terminals (the metal parts) inside the connector. See if they look burned or have a green tint indicating corrosion, especially if t
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