What does it mean?
B1601 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Left Solar Sensor Circuit Low .
Symptoms
- Engine cranks but does not start, or starts and stalls within a second or two
- Security indicator flashes and the immobiliser stays active
- One key works normally while another is rejected every time
- The problem appeared right after a key was cut, a module was replaced, or the battery went completely flat
- On the sensor variant, the climate system blows colder than commanded or ignores sunlight in automatic mode
Likely causes
- Key never programmed to this vehicle, such as an aftermarket, used or borrowed key
- Key programmed to a module that has since been replaced or reflashed, so the stored codes no longer match
- Transponder chip damaged or only partly readable, so the code arrives corrupted
- A second transponder in range being read instead of the intended key
- Weak or noisy signal from a damaged or misaligned antenna ring
- Low system voltage during cranking distorting the transmitted code
- Corrupted security memory inside the control module
- On applications where this code refers to climate control, a solar load sensor circuit reading low from a short to ground or a failed sensor
How to fix it
- Test each key on its own with no other keys or transponders nearby, and record which ones are accepted
- Establish whether the failing key was ever programmed to this vehicle before assuming a hardware fault
- Check battery condition and cranking voltage, because a low voltage read produces the same complaint
- Inspect the antenna ring and its wiring for damage before condemning the key
- Run the manufacturer security relearn procedure and follow its timed sequence exactly, as a missed step aborts the programming
- Program a new key only if the existing key fails the relearn with good wiring and voltage
- On the sensor variant, back-probe the sensor signal, compare it with the specified range and check the circuit for a short to ground