Body
Generic/SAE
OBD-II Fault Code
B2456: Aux Heater Coolant Sensor Circuit Short to Ground
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for B2456.
Cooling system
Use this category to narrow your checks before replacing parts.
High
Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.
What B2456 usually means
Aux Heater Coolant Sensor Circuit Short to Ground.
Common symptoms
Body/accessory warning lamp or feature not working; Temperature gauge abnormal; Overheating or slow warm-up possible
Likely causes
Low coolant; Faulty thermostat; Coolant temperature sensor/wiring fault; Cooling fan issue; Wire shorted to chassis/ground; Internal component short
Diagnostic checks
Check related fuses, connectors, grounds and switch/module power supply; Check coolant level only when engine is cool; Compare scan-tool temperature to actual temperature; Inspect harness for rubbing/pinch points and check resistance to ground
Repair guidance
Repair leaks, replace thermostat/sensor/fan component after confirming fault; Repair insulation/harness damage or replace internally shorted component
Verification after repair
Operate the affected body/accessory system and rescan