P0437

Code

Generic P — Powertrain

Catalyst Temperature Sensor Circuit Low Bank 2 Sensor 1

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 42 RU: 40

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Check Engine Light (MIL) illuminated
Reduced fuel economy or drivability complaints if ECM goes into limp strategy
Failed emissions test
Stored freeze-frame data showing low catalyst temperature reading for Bank 2 Sensor 1
Possible rough idle or hesitation if related to heater circuit faults or secondary diagnostics

Read live data: monitor catalyst temperature (Bank 2 Sensor 1) and compare with Bank 1 and expected warm-up behavior
Check freeze-frame and readiness/test status
Visually inspect sensor, connector, and wiring for damage, corrosion, or exhaust contact
Back-probe sensor connector: verify reference voltage (if applicable), signal voltage, and ground
Measure sensor resistance (with cool and warm engine if safe) and compare to manufacturer spec or compare to known-good sensor
Wiggle wiring harness while monitoring live data to find intermittent faults

Sensor type usually a thermistor (NTC) — resistance decreases as temperature increases
Typical signal voltage range varies by vehicle; expect measurable change with temperature (example: 0.1–4.9 V range on many vehicles)
At cold engine temps the sensor shows higher resistance / lower voltage; at hot temps it shows lower resistance / higher voltage (vehicle-specific)
Heater circuit (if present) should show proper supply voltage and controlled current when commanded
Compare Bank 2 Sensor 1 to Bank 1 Sensor 1 for similar trends during warm-up

Verify the code with a scan tool, record freeze-frame and live-data values for Bank 2 Sensor 1 and compare to Bank 1 Sensor 1.
Perform a visual inspection of the sensor, connector, and wiring for physical damage, corrosion, or contact with hot exhaust components.
Back-probe the sensor connector with the engine off and key on to check reference voltage (if applicable) and ground continuity. Repair any missing reference or poor ground.
With the engine at different temperatures (cold and warmed up) monitor sensor voltage/resistance. If the sensor does not change with temperature, suspect the sensor or heater circuit.
Check resistance of the sensor against manufacturer data or compare to a known-good sensor. Replace sensor if out of range.
If wiring appears suspect, perform continuity and short-to-ground/short-to-voltage checks. Repair or replace damaged harness or connector.
After repairs clear codes and perform a drive cycle or readiness test to verify the fault does not return. Re-scan for related codes.
If wiring and sensor pass tests but code persists, consider PCM/ECM diagnostic or specialist testing (uncommon).