Faulty catalyst temperature sensor on bank 2, where the internal thermistor has failed and reads lower than actual temperature.; Damaged or corroded wiring between the sensor and the PCM, such as a chafed wire shorting to ground or a broken connector pin.; Water intrusion into the sensor connector, causing a low-resistance path to ground and a low signal.; A short to ground in the signal circuit, often from a pinched harness near the exhaust or transmission.; PCM internal fault on the sensor input circuit, though this is less common than sensor or wiring problems.; Exhaust system modifications or leaks near the sensor that alter the temperature reading and set a low-signal code.

DTC codes / P04xx · Auxiliary emission controls / P0437

P0437Catalyst Temperature Sensor Low (Bank 2)

Q: What does code P0437 mean?

Catalyst Temperature Sensor Low (Bank 2). P0437 means the powertrain control module (PCM) has detected a low signal from the catalyst temperature sensor on bank 2, which is the side of the engine that does not contain cylinder number one. The sensor is a thermistor that changes resistance with temperature, and the PCM expects a voltage within a specific range; a low reading tells the computer the sensor circuit is shorted to ground or the sensor itself has failed.

P0437 means the powertrain control module (PCM) has detected a low signal from the catalyst temperature sensor on bank 2, which is the side of the engine that does not contain cylinder number one. The sensor is a thermistor that changes resistance with temperature, and the PCM expects a voltage within a specific range; a low reading tells the computer the sensor circuit is shorted to ground or the sensor itself has failed.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
A slight decrease in fuel economy if the PCM enters a default strategy that enriches the mixture.
In rare cases, a rough idle or hesitation when the engine is cold if the faulty sensor reading affects catalyst heating strategy.
Failed emissions inspection due to the stored code and pending monitor status.
No drivability complaints in most cases because the catalyst temperature sensor is primarily an emissions control device.

Common causes, most likely first

Faulty catalyst temperature sensor on bank 2, where the internal thermistor has failed and reads lower than actual temperature.
Damaged or corroded wiring between the sensor and the PCM, such as a chafed wire shorting to ground or a broken connector pin.
Water intrusion into the sensor connector, causing a low-resistance path to ground and a low signal.
A short to ground in the signal circuit, often from a pinched harness near the exhaust or transmission.
PCM internal fault on the sensor input circuit, though this is less common than sensor or wiring problems.
Exhaust system modifications or leaks near the sensor that alter the temperature reading and set a low-signal code.

How to diagnose and fix it

Connect a scan tool and record the freeze-frame data and sensor voltage reading for bank 2 catalyst temperature to confirm the low signal.
Visually inspect the sensor, connector, and wiring harness for damage, corrosion, or contamination, and repair any obvious faults.
Measure the sensor resistance with a multimeter and compare it to the manufacturer's temperature-resistance chart to verify sensor operation.
Backprobe the signal circuit at the PCM and check for a short to ground with the sensor disconnected; repair the harness if a short is found.
If the wiring and connector are good, replace the bank 2 catalyst temperature sensor with a quality direct-fit part.
Clear the diagnostic trouble codes and perform a road test to verify the repair and confirm the monitor runs to completion.

What the low signal really means

A low signal code does not automatically mean the sensor is bad; a shorted signal wire or a contaminated connector can produce the same low voltage reading and is often missed during a quick diagnosis.
The catalyst temperature sensor is used to protect the catalytic converter from overheating, so a false low reading can cause the PCM to alter fuel delivery and potentially mask a real overheating condition.
On many vehicles, the bank 2 catalyst temperature sensor is located after the second catalytic converter and is exposed to road splash, making water intrusion a frequent cause of low-signal codes.
Technicians sometimes replace the catalytic converter when this code appears, but the converter is rarely the cause of a low sensor signal; the fault lies in the sensor circuit or the sensor itself.
A faulty sensor can set P0437 without turning on the check engine light immediately if the fault is intermittent, so a pending code may be the only clue during a scan.

Can I keep driving with P0437?

You can usually continue driving with P0437 because the fault mainly affects emissions and does not typically cause a breakdown, but avoid prolonged idling or heavy loads until it is repaired. Have the vehicle diagnosed soon to prevent potential catalyst damage from incorrect fuel control and to ensure it passes emissions testing.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.