Faulty catalyst temperature sensor reading low or failed internally; Sensor signal wire chafed and shorted to ground, often near the exhaust or heat shields; Corroded, damaged or water-contaminated sensor connector causing a low signal; Sensor reference supply or ground wiring fault; Heat damage to the harness near the exhaust; Faulty engine control unit.

P0437

Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 1.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
37: FaultThe specific fault in that area

What it means

P0437 is the generic code for a low signal from the catalyst temperature sensor circuit on bank 2, sensor 1, which is the sensor at or just after the upstream catalyst on the bank not containing cylinder 1. The control unit saw the sensor signal voltage fall below the expected range, which points to a short to ground, a wiring fault or a failed sensor. Not every vehicle has catalyst temperature sensors, and their position and number vary by model and engine.

Symptoms

Engine management warning light on
Usually no change in driveability
Catalyst temperature or efficiency monitors may not complete
Possible failed emissions test
Occasionally reduced power or limp mode if the control unit uses the sensor to protect the catalyst

Possible causes

Faulty catalyst temperature sensor reading low or failed internallylikely
Sensor signal wire chafed and shorted to ground, often near the exhaust or heat shieldslikely
Corroded, damaged or water-contaminated sensor connector causing a low signalpossible
Sensor reference supply or ground wiring faultpossible
Heat damage to the harness near the exhaustpossible
Faulty engine control unitrare

How to diagnose

Read all stored and pending codes and the freeze frame data, and note any other catalyst, oxygen sensor or circuit codes.
Confirm which sensor is bank 2 sensor 1 on this engine, using model-specific information, as layouts vary.
Visually inspect the sensor, harness and connector for damage, corrosion, moisture, melted insulation or contact with the exhaust.
Check live data for the sensor reading with the engine cold and again when warm; a reading that stays very low or fixed suggests a fault.
With the connector unplugged, check the supply and ground at the harness side against the manufacturer's specification.
Test the signal wire for a short to ground and for continuity back to the control unit.
Measure the sensor resistance or output against the manufacturer's specification if one is available.
Clear the code and road test, then recheck live data to confirm the fault does not return.

How to fix

Replace the catalyst temperature sensor if it is faulty, using the correct part for the model and engine.
Repair or replace chafed or heat-damaged wiring and secure it away from hot components.
Clean, repair or replace a corroded or damaged connector and its terminals.
Correct any supply or ground wiring faults found during testing.
Only after all other causes are ruled out, diagnose the control unit and repair or replace it as the manufacturer advises.

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair. If power is reduced or other catalyst or misfire codes appear, have it checked sooner to avoid catalyst damage.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.