P0037 Code- HO2S Heater Control Circuit Low Bank 1 Sensor 2

What Does Code P0037 Mean

P0037 indicates that, for the engine to run correctly, the exhaust must have a specific air fuel ratio of 14.7 to 1 as determined by the Heated oxygen sensors (HO2S), which detects the oxygen content of the vehicle exhaust. This information is then sent to the Engine Control Module (ECM) to adjust the amount of fuel delivered to the engine. An HO2S is heated to ensure very rapid data transmission to the ECM’s closed loop system, which helps control emissions during start up and when the engine is cold or warming up.

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Possible symptoms

• Engine Light ON (or Service Engine Soon Warning Light)

Possible causes

• Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2
• Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 fuse
• Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 harness is open or shorted
• Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit poor electrical connection
• Faulty Engine Control Module (ECM)

Troubleshooting P0037

NOTE #1: It should be noted that code P0037 indicates a fault in the oxygen sensors’ heating control circuits, rather than issues with fuel/air metering. In cases where codes relating to fuel/air metering are present along with P0037, these codes must be resolved before starting an electrical diagnosis of code P0037.

NOTE #2: At the risk of overstating the case, code P0037 relates to oxygen sensors that are located after the catalytic converter. To avoid confusion, and prevent testing/replacement of the wrong oxygen sensors, always consult the repair manual to determine the location, color-coding, and routing of the wiring associated with #2 oxygen sensors.

NOTE #3: Check for, and repair all exhaust leaks before starting an electrical diagnosis of code P0037. Exhaust leaks can contaminate the atmospheric air used by oxygen sensors, which contamination can result in inaccurate readings.

Step 1

Record all fault codes and available freeze frame data. This data can be useful in cases where an intermittent fault is diagnosed later on.

Step 2

Perform a thorough visual inspection of all associated wiring and connectors. Look for damaged, shorted, burnt, or broken wiring and connectors. Replace wiring and/or connectors as required, and rescan the system to see if the code returns.

NOTE: On some applications, the input voltage is supplied through a fused circuit. Be sure to check associated fuses during the initial inspection of the wiring.

Step 3

If the code persists, perform reference, continuity, and resistance tests on all associated wiring. Input voltage must be equal to battery voltage (12.6 to 13.8-volts), so be sure to check that the battery is fully charged. Be sure to disconnect the sensor from the PCM before starting continuity checks to prevent damage to the controller.

Pay particular attention to the resistance of the sensor, which should be 8 Ohms, or very close to it. Compare the obtained resistance reading to the value stated in the manual, and replace the sensor if it deviates from the stated value. Remove the sensor from the exhaust system, and be sure to unplug the connector to get the most accurate resistance reading.

NOTE: Be aware that on some applications, the input voltage is supplied by the PCM, and in these cases the input voltage will not be routed through a fuse. On some applications the ground is also supplied by the PCM in Key-On-Engine-Off mode, while on other applications the engine needs to run for a ground to be present. Consult the manual on this point.

Step 4

While the oxygen sensor is removed from the system, inspect the element for signs of discoloration, or the presence of deposits. Some aftermarket fuel and oil additives contain silicone-based compounds that can cause deposits to form on spark plugs and oxygen sensors. Note that oxygen sensors cannot be cleaned to remove deposits; the only reliable remedy is to replace the sensor, and not to use any sort of oil/fuel additives

Step 5

It deposits and discoloration is found, replace the sensor, and retest the system to verify that all voltages/resistances fall within the manufacturers specifications. If all readings check out OK, start the engine and allow the PCM to enter closed loop operation.

If the sensor was replaced and the wiring is in good shape, the code scanner should indicate a reading that falls close to the mid-point between a rich-, and lean running condition. A variation of around 100-, to 200 millivolts to either side of the mid-point is acceptable, but the reading should remain constant if the engine speed does not change.

Changing the engine speed should produce an almost immediate change in the displayed reading; if no change is observed, or there is a significant time lag (more than 5 to 8 seconds or so) before the reading changes, the sensor is defective- assuming of course that there is no damage or corrosion present on the connector.

Check the connector again; if it is in a less-than-perfect condition, repair/replace it, and check the sensors’ operation again. If the fault persists after repairing the connector, replace the sensor if it was not replaced previously after the inspection for discoloration or the presence of deposits.

NOTE: Bear in mind that the overall state of repair of an engine can have significant effects on the performance of oxygen sensors. If there are no electrical issues in the heater control circuit of an oxygen sensor, there is little point in trying to diagnose oxygen sensor related issues if the engine is affected by excessive oil burning, poor combustion, vacuum leaks, exhaust leaks, or other issues that affect the overall performance of the engine and/or exhaust system.

Step 6

At this point, the repair should be complete, but to be sure, clear all codes and test drive the vehicle to see if the code returns. In the unlikely event that the code does return, there may be an intermittent fault present.

Finding and repairing an intermittent fault can be extremely challenging, and in some cases, the fault may have to be allowed to worsen before an accurate and definitive repair can be made.

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