DTC Detection Logic

WARNING: This page is about a different car, the 2019 Nissan NV3500 HD, 2019 Nissan NV2500 HD, and 2019 Nissan NV1500. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

If DTC is displayed along with DTC U1000 or U1010, first diagnose the DTC U1000 or U1010. Refer to DTC Logic or DTC Logic .
If there is an open circuit in the ambient sensor, the front air control registers extreme cold [-30 deg. C (-22 deg. F)] and adjusts the temperature control warmer.

DTC

Items

(CONSULT screen terms)

Diagnostic item is detected when...

Possible cause

B257B

AMBIENT SENSOR

Detected temperature at ambient sensor 55 deg. C (131 deg. F) or more

Ambient sensor
Front air control
Harness and connector
(Ambient sensor circuit is open, or there is a short in the circuit)

B257C

Detected temperature at ambient sensor -30 deg. C (-22 deg. F) or less