P0437 OBD-II Trouble Code: Catalyst Temperature Sensor Low (Bank 2)

Diagnostic Trouble Code (DTC): P0437

P0437 code definition

If the PCM has stored the P0437 code, it means that a three-way catalytic converter is not working as efficiently as it should be according to the manufacturer’s specifications. This code is frequently accompanied by an oxygen sensor code, which should always be diagnosed and repaired first before attempting to diagnose and repair the P0437 code.

What the P0437 code means

The PCM calculates how efficiently each catalyst in each converter is performing, through a variety of sensors, particularly the upstream and downstream oxygen sensors. These sensors’ readings are affected by the fuel conditions and other factors within the engine. The upstream sensor reading is supposed to fluctuate, while the downstream sensor reading is supposed to be fairly steady. If at any time, the readings from the sensors are too similar, or do not fall within the manufacturer’s parameters, the P0437 code will be stored.

What causes the P0437 code?

In many cases, the P0437 code is caused by a faulty catalytic converter. Other causes may include:

• Faulty catalyst temperature sensor
• Open or shorted catalyst temperature sensor harness
• Poor electrical connection within the catalyst temperature sensor circuit

There are several underlying causes to a faulty catalytic converter, such as:

• Using the incorrect fuel
• Faulty coolant temperature sensor
• Faulty fuel injection component
• Contaminated oil
• Faulty spark timing
• Leaking exhaust manifold
• Leaking down pipe
• Leaking flex hose
• Faulty mass air flow sensor
• Faulty manifold air pressure sensor
• Faulty pressure regulator

What are the symptoms of the P0437 code?

In many cases, the only symptom that a vehicle owner may observe is the illumination of the Check Engine lamp. If any of the converter components have melted or broken, there may also be a decrease in engine performance, a hissing noise during acceleration, or even an inability to start the vehicle at all.

How does a mechanic diagnose the P0437 code?

The first step in any diagnostic process is to verify the code with an OBD-II scanner. After this process, the mechanic should begin by examining the electrical components for corroded or loose elements, and the exhaust system for leaks. If an issue is present in either area, this issue should be repaired, and the code should be cleared and the system retested.

If, after the mechanic completes these two diagnostic procedures, the code returns, it is most likely that the catalytic converter is bad. The mechanic should continue attempting one repair at a time, clearing the code and retesting as they go, to ensure they pinpoint the problem.

Common mistakes when diagnosing the P0437 code

In most cases, the biggest issue that technicians report is a previous repair that wasn’t in-depth enough. It’s important to find the reason for the faulty catalytic converter, so that the issue does not occur again after a new converter is installed.

The next most common issue is a mistakenly blamed oxygen sensor. Because an oxygen sensor code can be present at the same time as the P0437 code, mechanics may replace this part right away; but the oxygen sensor should be tested for proper operation before it is replaced, because it is usually not to blame.

How serious is the P0437 code?

If the P0437 code is being detected, the vehicle will most likely still be drivable. Unless there are serious breakages within the converter components, this is considered a mild issue. It may affect the vehicle’s ability to pass an emissions test, and it should be repaired when time allows; but it is not an emergency repair that must be performed ASAP.

What repairs can fix the P0437 code?

In most cases, repairing the faulty catalytic converter, and repairing the underlying issue that caused the fault, will fix the P0437 code. Other repairs may include:

• Replacing a faulty catalyst temperature sensor
• Repairing an open or shorted catalyst temperature sensor harness
• Repairing a poor electrical connection within the catalyst temperature sensor circuit

Need help with a P0437 code?

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