OBD-II trouble code
P0437: Catalyst Temperature Sensor Low Input (Bank 2)
The bank 2 catalyst temperature signal is below the floor the chart allows. Confirm whether the sensor is an NTC thermistor or a thermocouple before a low voltage is read as a hot converter. The harness route comes from the diagram.
Quick facts
- System
- Powertrain
- Category
- Emissions / Catalyst
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $80 – $650
- DIY difficulty
- Intermediate DIY
Browse every code in P0400–P0499, or start from the full code library.
What does P0437 mean?
Low input is a statement about volts, not about degrees. On an NTC thermistor, resistance falls as temperature rises, so a low signal is the direction a hot converter would produce, and it is also the direction a short to ground produces. A thermocouple is inverted, so the same voltage means the opposite thing until the diagram names the sensor. The scan tool can display a temperature the exhaust is not at. The sensor type is confirmed before that number is believed.
A low signal on the NTC arrangement is tested as a short to ground: insulation on hot metal, moisture in the connector, a chafe at a bracket, or an element shorted inside the sensor. Those are the branches. They are not a ranking.
Where to look for the short is the harness route on the diagram, not a rule that bank 2's lead is always the longer one. Follow the run the diagram draws, whether it crosses the engine, follows the bulkhead, or passes the bellhousing. Start where that run lies on hot metal or a bracket edge. The sensor is tested after that wire.
If P0427 is stored with P0437, read the diagram for a shared sensor ground or a shared section of loom, and test that before two separate chafes are assumed. The chart's module branch comes after those wires test normal. P0437 alone is tested on bank 2's own circuit.
Whether the calibration enriches, pulls timing, or limits load when it believes the converter is too hot is in the service information for this vehicle. Do not assume that strategy is present. A fuel-trim change is checked against the freeze frame, not inferred from the code title.
Common causes
- Signal wire shorted to ground where the bank 2 run crosses exhaust pipework or a bracket edge
- Insulation melted through where the loom rests on the exhaust crossover or a heat shield
- Water or corrosion bridging the signal and ground terminals inside the bank 2 connector
- Sensor element shorted internally after thermal cycling
- Harness pinched or trapped during intake manifold, spark plug or exhaust work on bank 2
- Missing or broken heat shield allowing the loom to contact hot metal it was never meant to touch
- Damaged sensor ground circuit shared with the bank 1 sensor, when both banks report low together
- Module input, checked only after the sensor and the wiring have been compared with the chart
Symptoms
- Check engine light with P0437 stored
- Bank 2 catalyst temperature displayed as an implausibly high value on a scan tool
- Bank 1 temperature reading normally at the same moment, which localises the fault
- A fuel-trim change only if this calibration's protection strategy enriches, which the service information states
- Emissions monitors not completing, so the vehicle cannot be tested
- Other codes for components sharing the same damaged section of loom
Diagnostic steps
- 1.Establish the sensor type before interpreting direction. On a thermistor low voltage indicates high temperature; on a thermocouple the relationship is reversed.
- 2.Read both banks' catalyst temperature values together. Bank 2 at an extreme with bank 1 sitting at a plausible ambient number confirms the fault is local rather than shared.
- 3.Check whether P0427 is also stored. Both banks low at once implicates the shared sensor ground, a common section of harness or the module, rather than two coincidental chafes.
- 4.Trace the bank 2 sensor lead along its full route with the crossing point as the priority — over the exhaust crossover, around the bulkhead or under near the bellhousing, wherever this vehicle routes it.
- 5.Confirm the sensor type before an unplug test. On a pull-up NTC circuit, unplugging the sensor lets the signal rise, and a signal that stays low with the sensor disconnected is in the harness. A thermocouple is not read that way. Use the test the diagram's sensor type calls for.
- 6.With the sensor disconnected, check the signal wire for continuity to ground back to the module connector.
- 7.Inspect the connector for moisture and corrosion, which produce a resistive rather than a dead short and can come and go with the weather.
- 8.Measure sensor resistance at ambient and compare it against specification, or against the bank 1 sensor measured the same way.
- 9.Repair chafed wiring properly — reroute and protect the section rather than only taping it — since a wire that has found the exhaust once will find it again.
- 10.Do not condemn the converter on this code. Confirm or exclude P0430 separately.
Repair cost
$80 – $650
Read the printed bracket as a planning span, not a quoted price. The low end names a wiring repair after the short to ground has been found and rerouted. The high end names the sensor after the harness test has passed it. Do not assume the calibration has been enriching. That strategy, if it exists, is in the service information.
Estimate your repair
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Open the Repair Cost Estimator with wiring harness / circuit repair preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.