What it means
The transmission fluid pressure sensor/switch D reports a circuit low fault. Hydraulic pressure feedback for shift control is unreliable on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Transmission pressure sensor/switch D sends the control module an electrical signal used to monitor hydraulic pressure for shift control. P0877 sets when the D-circuit signal is lower than expected, which can happen if its signal wire is grounded, the sensor is internally shorted, or connector contact is poor.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save freeze-frame data and review live sensor D data to confirm the low signal and note the gear or conditions when it occurs.
- Inspect sensor D's connector and harness for corrosion, damaged insulation, or wiring pinched against the transmission or chassis.
- Check D-circuit connector pins for corrosion or poor contact and confirm the plug is fully seated.
- Use vehicle wiring information to test the D signal wire for a short to ground and check its reference and ground circuits against the manufacturer's specification.
- If the wiring and connections pass, test pressure sensor/switch D under the specified conditions to determine whether it is internally shorted.
Common fixes
- Clean corroded terminals and secure the sensor D connector.
- Repair a signal wire short to ground or damaged wiring in the D circuit.
- Replace pressure sensor/switch D if it is internally shorted and the circuit is sound.
- Repair poor terminal contact that is pulling down the D-circuit signal.
Can I keep driving?
Limit driving and avoid towing or hard acceleration, especially if shifting is harsh, slipping, or the transmission is in limp mode. A low D-circuit signal can disrupt shift control, and continued slipping can damage the transmission.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.