P0870 Transmission Fluid Pressure Sensor / Switch C Circuit
OBD-II Trouble Code Technical Description
Transmission Fluid Pressure Sensor / Switch "C" Circuit
What does that mean?
This generic powertrain/engine diagnostic trouble code typically applies to all OBD-II equipped vehicles including but not limited to Nissan, Dodge, Chrysler, Honda, Chevrolet, GMC, Toyota, etc. but seems to be most commonly seen on Nissan 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 "C" input does not match normal operating voltages stored in the PCM/TCM's memory. It may also be due to internal mechanical issues inside the transmission. Refer to a vehicle specific repair manual to determine which is the "C" circuit for your particular vehicle.
P0870 is typically an electrical circuit (TFPS sensor circuit) issue, although as previously stated this code may also be set due to mechanical issues (internal leaks, cracked or missing check balls in the valve body, low system operating pressure/main line pressure, stuck valve in the valve body). 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 "C" circuit codes:
P0871 Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance P0872 Transmission Fluid Pressure Sensor/Switch "C" Circuit Low P0873 Transmission Fluid Pressure Sensor/Switch "C" Circuit High P0874 Transmission Fluid Pressure Sensor/Switch "C" 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 P0870 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:
Open in the signal circuit to the TFPS sensor - possible Short to voltage in the signal circuit to the TFPS sensor - possible Short to ground in the signal circuit to the TFPS sensor - possible Failed TFPS Sensor – likely Internal mechanical transmission issue - possible 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 P0870, 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 P0870.
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 insid
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