P0037

DTC P0037

CIRCUIT DESCRIPTION
The DTC P0037 Heated Oxygen Sensor (HO2S) Heater Control Circuit Low Voltage Sensor 2 diagnostic monitors the operation of the HO2S 2 heater circuit. The heaters in the oxygen sensors increase the amount of time the sensor spends in Closed Loop fuel control operation or catalyst monitoring operation. The oxygen sensor heater is required by the post-catalyst HO2S 2 in order to maintain the high operating temperatures. The heater helps provide accurate oxygen content readings of the engine exhaust by the HO2S.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0037 Heated Oxygen Sensor (HO2S) Heater Control Circuit Low Voltage Sensor 2

CONDITIONS FOR RUNNING THE DTC
- The battery is between 20.5-16 volts.
- The engine has been operating for at least 10 seconds.
- The heater control circuit duty cycle is more than 50 percent.
- No current misfire is detected.
- DTC P0037 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
- The HO2S 2 heater is commanded ON for more than 0.2 seconds.
- The HO2S 2 heater current is less than 0.8 amps.
- The condition exists for more than 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The powertrain control module (PCM) illuminates the malfunction indicator lamp (MIL).
- The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.
- The PCM will turn OFF the heater in the oxygen sensor.

CONDITIONS FOR CLEARING THE MIL/DTC
- The MIL turns OFF after 3 consecutively passing trips without a fault present.
- A History DTC clears after 40 consecutive warm-up cycles without a fault.
- Use the scan tool Clear DTC Information function in order to clear the DTC.

TEST DESCRIPTION

Step 1 - Step 12:

Step 13 - Step 15:

The numbers below refer to the step numbers in the diagnostic table.
1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. This step checks whether the malfunction that caused the DTC P0037 is still present. Operating the vehicle in check mode enhances the diagnostic capabilities of the PCM. The HO2S Heater diagnostic can be monitored on the scan tool under the I/M System Information selection of System Information. When the HO2S Heater test displays a YES status, indicating that the oxygen sensor heater diagnostic is completed, check for a DTC P0037 in the Last Test Failed screen of the scan tool. If there is no DTC P0037 displayed the HO2S heater diagnostic has run and passed, indicating that no malfunction was present this time. The DTCs MUST be cleared in order to view the Current Status of the system diagnostics being performed. Do not forget that I/M System Information tests only indicate that the test has run, not whether the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved. For additional information on check mode operation refer to Powertrain Control Module Diagnosis. Testing and Inspection
9. This step tests the HO2S ground circuit at the PCM. In order for the PCM to operate the HO2S 2 heater control circuit, the ground circuit to C2-6 must be good.