Transmission Fluid Pressure Sensor/Switch "C" Circuit Low
P0872 indicates the transmission fluid pressure sensor/switch C circuit is reading lower than expected, preventing the PCM/TCM from accurately monitoring transmission hydraulic pressure. This electrical fault can cause the transmission to shift erratically or default to limp mode, as the control module cannot properly regulate pressure-dependent functions.
What You Might Notice
- Transmission shifting erratically or harshly
- Transmission entering limp mode or reduced power mode
- Check engine light illuminated
- Delayed gear engagement or slipping between gears
- Transmission fluid pressure readings unavailable on diagnostic scan
Most Common Causes
- 1
Short to ground in TFPS signal circuit
The wiring harness or connector pins have shorted to ground, causing the sensor signal to read low. This is the most common electrical failure for this code.
- 2
Failed transmission fluid pressure sensor
The TFPS sensor itself has failed or has an internal short, preventing it from sending accurate pressure readings to the PCM/TCM.
- 3
Corroded or damaged connector pins
The connector pins at the sensor or PCM/TCM have corroded, cracked, or been damaged, breaking the signal circuit connection.
- 4
PCM/TCM failure
The transmission control module has failed and cannot properly receive or interpret the pressure sensor signal, though this is rare.
How to Diagnose It
- 1
Check Short to ground in TFPS signal circuit — The wiring harness or connector pins have shorted to ground, causing the sensor signal to read low. This is the most common electrical failure for this code.
- 2
Check Failed transmission fluid pressure sensor — The TFPS sensor itself has failed or has an internal short, preventing it from sending accurate pressure readings to the PCM/TCM.
- 3
Check Corroded or damaged connector pins — The connector pins at the sensor or PCM/TCM have corroded, cracked, or been damaged, breaking the signal circuit connection.
- 4
Check PCM/TCM failure — The transmission control module has failed and cannot properly receive or interpret the pressure sensor signal, though this is rare.
How to Fix It
- 1
Inspect and repair wiring harness
Locate the transmission fluid pressure sensor C circuit wiring and inspect for cuts, abrasions, or corrosion. Repair any damaged sections and verify the circuit continuity from sensor to PCM/TCM.
- 2
Clean or replace connector
Disconnect the TFPS sensor connector and inspect for corrosion, bent pins, or contamination. Clean with electrical contact cleaner or replace the connector if damaged.
- 3
Replace transmission fluid pressure sensor
Remove and replace the transmission fluid pressure sensor C with a new OEM or quality replacement. Refill transmission fluid to proper level after replacement and clear the fault code.
- 4
Reprogram or replace PCM/TCM
If wiring and sensor checks pass, the PCM/TCM may require reprogramming or replacement. This requires specialized diagnostic equipment and is typically performed by a dealership.
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