Error P0037 – how to fix?

Error code definition P0037

P0037 is the code for the HO2S Low heating control circuit (Bank 1, Sensor 2).

What does the code P0037 mean

Code P0037 indicates that the engine must have an air-to-fuel ratio of 14.7 to 1 for the engine to function properly as determined by Heated Oxygen Sensors (HO2S) which detect the oxygen content of the vehicle exhaust. This information is sent to the engine control module (ECM) to adjust the amount of fuel delivered to the engine. The HO2S system is heated to provide very fast data transmission to the ECM’s closed-loop system, which helps control exhaust emissions at start-up and when the engine is cold or warm.

What causes the code P0037?

If the code clears and is reset and then the Check Engine light and the OBD-II code reappear, then the HO2S sensor for Engine Bank 1 and Sensor # 2 which is on the back of the catalytic converter is not sending the correct information to the ECM and it may be damaged or defective. The sensor may have a damaged internal heating element, or it may have the wrong ground, a 12-volt battery input, or a bad connector. ECM failure is quite rare.

What are the symptoms of the P0037 code?

The ECM detects that the O2 sensor heater circuit is low current or open circuit and enters failure mode until the ignition is turned OFF. The failsafe mode causes different discomforts depending on the vehicle, vehicle manufacturer, and ECM programming. This safe mode will continue until the problem is fixed. Some of the most common problems when driving in emergency mode can be jitter, erratic operation and low power. The Check Engine indicator light will illuminate when the ECM detects a low control circuit level.

How can a mechanic diagnose the code P0037?

P0037 is only diagnosed with the OBD-II scanner. The mechanic needs to reset the OBD-II code and test the vehicle to see if the code returns. If it returns, the mechanic should check both power and ground to the sensor, including the wiring and the sensor. Many of the problems with this code are wiring related due to the heat of the exhaust gases.

The most common errors when diagnosing the code P0037

Do not replace the HO2S system immediately before thoroughly inspecting all associated wiring and connectors. The mechanic should make sure that the sensor has a voltage of 12 volts and that the ground is good. Also check both sides of the connector wiring to make sure the connector is good.

How serious is the P0037 code?

Code P0037 is usually preceded by the appearance of a Check Engine light on the vehicle’s dashboard while driving. The vehicle may still run, but must be properly diagnosed as soon as possible to avoid further problems such as sensor loop errors, high fuel consumption, malfunction or damage to other components.

Often times, if the Check Engine light illuminates immediately after startup, the OBD-II system may be reset and the vehicle will operate normally.

What repairs can remove the code P0037?

The most common potential repairs to fix code P0037 are as follows:

1. Have an authorized technician check the code with a scanner. Reset fault codes and perform road test.
2. If P0037 returns, perform the test procedure. You may have a few problems, but damaged wiring due to excessive exhaust heat is the most common. Before replacing a sensor, make sure that the wiring is good and has the correct voltage and ground for the sensor.

Test procedure

With the key on and the engine off, check with a voltmeter that the voltage from the battery fuse to the heater element is 12+ V. If there is no voltage, repair the open or short in the 12-volt supply circuit by determining first if the blown fuse must be replaced for a short circuit. If battery power is intact, disconnect the ground (control) circuit from the ECM wiring connector and check the circuit resistance. If resistance is infinite, repair open circuit. If the control circuit works, suspect a faulty O2 sensor. Replace and check again.

After having experienced this problem in the past, the most common problem is damage to the sensor wiring due to improper installation or damage to the wiring clamps, causing the pipes to touch the exhaust system, including the catalytic converter, which is the hottest part of the exhaust system. It is very likely that the rear sensor will be removed or exposed to physical damage during exhaust or powertrain work, with many potential problems. If the wiring of the sensor itself is damaged, do not attempt to repair it as it most likely will not function properly. In such cases, simply replace the sensor.

Additional notes regarding code P0037

Many vehicles over 100,000 km have temporary problems with the sensors, which often occur during starting or prolonged stress on the driveline. If the Check Engine light comes on and the vehicle appears to be operating normally, the OBD-II system can be reset using a scan tool and the problem may not recur. Therefore, it is important to check the fault and reset it before making any repairs.