P0872 code definition
A P0872 trouble code refers to a problem detected by the Powertrain Control Module (PCM) with the fluid pressure within the transmission. Some vehicle PCMs place the transmission into Limp-in mode in addition to storing a code and illuminating the Check Engine light. Related trouble codes include a P0870, P0871, P0873, and P0874 code.
What the P0872 code means
A P0872 trouble code means that the transmission fluid pressure has exceeded or fallen below limits set by the manufacturer.
What causes the P0872 code?
A transmission leak causing a low fluid condition is one cause of a P0872 trouble code. Additional causes include a defective high pressure pump, a malfunctioning transmission temperature sensor, an overheating engine, a slipping or malfunctioning transmission, or a faulty PCM.
What are the symptoms of the P0872 code?
Some common symptoms of a P0872 trouble code include the smell of overheated transmission fluid, sometimes accompanied by smoke. In addition to these signs, the transmission might also slip or fail to engage.
How does a mechanic diagnose the P0872 code?
To diagnose a P0872 trouble code, the mechanic needs to gather certain tools, including an OBD-II scanner, a manufacturer's wiring diagram, and a digital volt/ohmmeter. Once they have the proper tools, the mechanic can then proceed to diagnose the trouble code by taking the following steps:
- Using the manufacturer's wiring diagram, carefully inspect the PCM wiring, connectors, and related components.
- Examine the transmission fluid for any abnormalities or burnt smell. The mechanic should also look for any leaks.
- If abnormalities or a burnt smell are detected, remove the transmission pan and look for any debris that might signify damage.
- After making the necessary repairs, clear the P0872 trouble code and test the system to see if the code returns.
- Connect the OBD-II scanner to the diagnostic connector and downloading any stored trouble codes or freeze frame data.
- Once the necessary repairs have been made, the mechanic should fill the transmission with fluid, clear the code, and then start the vehicle, allowing it to reach a normal operating temperature. Test drive the vehicle to see if the trouble code returns.
- Unplug the electrical connector from the transmission temperature sensor and test it for reference voltage and ground signal using the volt/ohmmeter.
- If both are present, test the resistance of the sensor and compare it to the manufacturer's specifications.
- The mechanic should also check the vehicle's fuses to make sure none are blown.
- If all of the circuits and components check out, disconnect the PCM electrical connector and test the continuity and resistance between the PCM and the transmission temperature sensor.
- Finally, the mechanic should then clear the code and re-test the system to see if the code returns.
Common mistakes when diagnosing the P0872 code
When diagnosing and repairing a P0872 trouble code, mistakes comonly made by mechanics range from fixing a transmission leak while not realizing the low fluid condition has damaged the transmission internally to rebuilding the transmission when unnecessary just because the transmission overheated.
How serious is the P0872 code?
When a vehicle PCM stores a P0872 trouble code it is important to have the problem diagnoses and fixed as soon as possible to prevent further potential transmission damage.
What repairs can fix the P0872 code?
The mechanic should make repairs to the transmission in the following order:
- Replace any faulty or otherwise damaged wiring, connectors, or components.
- Rebuild the transmission if debris is detected in the transmission pan after further inspection.
- The mechanic must also install a new torque converter as a part of the transmission rebuilding process.
- Repair any leaks found in the transmission.
- Replace the transmission temperature sensor if it test as faulty.
- Replace any blown fuses detected, making sure to fix any problems that might be causing the fuses to blow in the process.
- Replace the PCM if the problem lies there.
Need help with a P0872 code?
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This article originally appeared on YourMechanic.com as P0872 OBD-II Trouble Code: Transmission Fluid Pressure Sensor/Switch C Circuit Low and was authored by Cheryl Knight.