P1459
Heated Catalyst Heater Power Supply Open Circuit Bank 2.
- BMW
- Powertrain
- Manufacturer code
- Low severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 4
- AreaAuxiliary emission controls
- 59
- FaultThe specific fault in that area
What it means
On BMW, P1459 means the engine control unit has detected an open circuit in the power supply to the heated catalyst heater on bank 2. The control unit expected to see the heater supply respond when it was commanded on, but saw no voltage or current, so the circuit is considered broken. Whether the car has a heated catalyst, and its layout, depends on model and engine, so check the wiring diagram for the specific vehicle.
Symptoms
- Engine warning light on
- Possible increase in cold-start emissions
- Other catalyst or emissions-readiness codes stored alongside it
- Failed emissions test or monitors not completing
- Usually no change in how the car drives
Possible causes
- Open circuit, chafed wire or damaged loom in the bank 2 heater supply wiringlikely
- Corroded, loose or heat-damaged connector at the heater or control unitlikely
- Blown fuse or faulty relay feeding the catalyst heater supplylikely
- Failed heater element inside the bank 2 catalyst (open internally)possible
- Low or unstable battery or charging voltage affecting the circuit monitoringpossible
- Faulty output driver in the engine control unitrare
How to diagnose
- Read all stored codes and freeze frame data, noting any related supply voltage, catalyst or battery voltage faults, then check for applicable technical bulletins for the model and engine.
- Confirm from the wiring diagram that the vehicle has a heated catalyst on bank 2 and identify the fuse, relay, connectors and control unit pins involved.
- Visually inspect the bank 2 heater wiring and connectors for heat damage, chafing, corrosion, water ingress and poor pin tension.
- Check the relevant fuse and relay, and test the relay operation and its supply and earth.
- With the connector disconnected, check for supply voltage at the heater feed when the control unit commands it, following the diagram for the correct conditions.
- Test the continuity of the supply wire end to end, and check for shorts to earth or other circuits.
- Measure the heater element resistance at the catalyst against the manufacturer specification.
- Check battery condition and charging voltage, then clear the code and retest to see if it returns.
How to fix
- Repair or replace damaged wiring and renew any corroded or damaged connector terminals.
- Replace the blown fuse only after finding out why it failed, and replace a faulty relay.
- Replace the bank 2 catalyst or heater assembly if the element is open circuit, using a part suitable for the model.
- Restore correct battery and charging system condition if voltage is low or unstable.
- Replace or repair the engine control unit only after wiring, power and the heater have all been proved good.
Can I keep driving?
Low severity
The car can normally be driven while you arrange a repair, as this fault rarely affects driveability. Emissions may be higher until it is fixed, so book it in soon.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.