P07BB

What it means

P07BB means the transmission control unit has found a fault on the second (B) park position sensor or switch circuit, either a signal that is implausible or one that is reading low. The control unit compares this input with the other park/range inputs and expects them to agree with the selector position. How the sensor is built and which signals it is checked against varies by model and transmission, so confirm this in the vehicle-specific data.

Symptoms

• Warning light on, possibly with a transmission or gearbox fault message
• Engine will not start or only starts intermittently in Park or Neutral
• Gear selector display flickering, wrong or missing the P position
• Reverse lights, shift lock or key release not working properly
• Harsh or delayed engagement, or the transmission defaulting to a limited mode
• Vehicle rolling more than expected, or the parking position not being recognised

Possible causes

• Damaged wiring, chafed insulation or a short to ground on the park position sensor B circuitlikely
• Corroded, loose or contaminated connector at the sensor, range switch or transmission control unitlikely
• Faulty park position sensor/switch or range sensor assembly (internal fault or wear)likely
• Selector linkage or cable out of adjustment, so the position does not match the sensorpossible
• Low or unstable supply or reference voltage to the sensor, from a poor earth or weak batterypossible
• Transmission fluid contamination or leakage reaching an internal sensor or connectorpossible
• Fault inside the transmission control unitrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting which selector position and what conditions were present, and check for related range sensor or start-inhibit codes
2. Check battery condition and charging voltage, as low voltage can cause false sensor faults
3. Inspect the sensor wiring and connectors for chafing, fluid ingress, corrosion, bent pins and poor retention
4. Watch live data for the park and range sensor signals while moving the selector through each position, and check they agree and change cleanly
5. Check the selector cable or linkage for correct adjustment and free movement against the selector position
6. Measure the sensor supply, signal and earth at the connector against the manufacturer's specification, and do a wiring continuity check for high resistance or shorts
7. Check the transmission for fluid leaks and the fluid level and condition, following the model's procedure
8. If the wiring and sensor test fine, check for a transmission control unit fault using the manufacturer's procedure

How to fix

• Repair or replace damaged wiring and clean or replace corroded or damaged connectors
• Replace the park position sensor/switch or range sensor assembly if it fails testing, then adjust it as the manufacturer specifies
• Adjust or repair the selector cable or linkage so the position matches the sensor
• Restore a good power supply and earth by repairing the battery, charging or earth connections
• Fix any fluid leak that is contaminating the sensor or connector, and correct the fluid level
• Repair or replace the transmission control unit only after the other causes are ruled out, and have it programmed to the vehicle

Can I keep driving?

Nearby codes

• P07BAGenericTransmission Park Position Sensor/Switch B Circuit High
• P07BCGenericTransmission Park Position Sensor/Switch B Circuit Performance High