P07BF

What it means

P07BF means the transmission control unit has seen the signal voltage from input/turbine shaft speed sensor 'A' fall below the expected range. The fault is flagged when the circuit reads low, which points to a short to earth, an open circuit, a poor connection or a failed sensor. The exact sensor location and signal type depend on the vehicle and transmission.

Symptoms

• Gearbox warning light or malfunction indicator lamp on
• Transmission going into limp-home mode, often stuck in one gear
• Harsh, delayed or erratic gear changes
• Speedometer or rev reading behaving oddly on some models
• Torque converter lock-up not working, with poor economy
• Transmission shifting only manually or not selecting some gears

Possible causes

• Faulty input/turbine shaft speed sensorlikely
• Damaged, chafed or shorted sensor wiring (short to earth or open circuit)likely
• Corroded, loose or contaminated connector at the sensor or transmission connectorlikely
• Fluid leak or contamination affecting the sensor or its connectorpossible
• Damaged or magnetically contaminated tone ring or rotating speed target, or metal debris on the sensor tippossible
• Faulty transmission control unit or internal mechatronic/valve body wiring (on units with an integrated sensor)rare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting speed, gear and temperature when it set, and check for other speed sensor or communication faults.
2. Check the transmission fluid level and condition on models with a dipstick or check procedure, and look for leaks around the sensor and connector.
3. Visually inspect the sensor wiring and connector for chafing, heat damage, corrosion, bent pins and water ingress.
4. With the ignition off, wiggle-test the harness while watching live input speed data for dropouts.
5. Compare live input shaft speed with engine speed and output speed to see if the signal is missing or implausible.
6. Using the manufacturer's wiring diagram, check the sensor's supply, signal and earth circuits for open circuits, shorts to earth and resistance.
7. Check the sensor's resistance or output against the manufacturer's specification, as the method depends on whether it is a Hall-effect or inductive type.
8. Remove the sensor if accessible and inspect the tip for debris and damage, and inspect the target ring where the design allows.

How to fix

• Replace the input/turbine shaft speed sensor if it is out of specification or gives no signal.
• Repair or replace damaged wiring and fix any shorts to earth or open circuits.
• Clean, repair or replace corroded or loose connectors and secure the harness.
• Fix any fluid leak and correct the fluid level or condition as the manufacturer specifies.
• Repair or replace a damaged tone ring or speed target, or the affected transmission component, if the fault is mechanical.
• Replace or reprogram the transmission control unit only after the wiring and sensor are confirmed good and the manufacturer advises it.

Can I keep driving?

Nearby codes

• P07BEGenericTransmission Park Position Sensor/Switch A/B Correlation
• P07C0GenericInput/Turbine Shaft Speed Sensor A Circuit High