DTC P0037

DTC P0037	HO2S heater circuit low input
DETECTION CONDITION	The PCM monitors the HO2S heater control voltage when the PCM turns the HO2S heater on. If the control voltage is less than 90 % of the battery voltage, the PCM determines that the HO2S heater control circuit voltage is low. Diagnostic support note This is a continuous monitor (A/F sensor heater, HO2S heater). The MIL illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM. PENDING CODE is available if the PCM detects the above malfunction condition during the first drive cycle. FREEZE FRAME DATA (Mode 2/Mode 12) is available. The DTC is stored in the PCM memory.
POSSIBLE CAUSE	HO2S connector or terminals malfunction Open circuit or short to ground in HO2S heater power supply circuit Short to ground in wiring harness between ignition relay and HO2S terminal C HO2S heater power supply circuit related fuse malfunction Open circuit in wiring harness between ignition relay and HO2S terminal C HO2S heater malfunction Short to ground in wiring harness between HO2S terminal D and PCM terminal 2BE PCM connector or terminals malfunction Open circuit in wiring harness between HO2S terminal D and PCM terminal 2BE PCM malfunction

DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA (MODE 12) AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS (A/F sensor heater, HO2S heater related) been recorded?	Yes	Go to the next step.
1		No	Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2	VERIFY RELATED SERVICE BULLETINS AVAILABILITY Verify related Service Bulletins availability. Is any related Service Bulletins available?	Yes	Perform the repair or diagnosis according to the available Service Bulletins. If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	INSPECT HO2S CONNECTOR AND TERMINALS Turn the ignition switch off. Disconnect the HO2S connector. Inspect for poor connection (such as damaged/pulled-out pins, and corrosion). Is there any malfunction?	Yes	Repair or replace the connector or terminals, then go to Step 9.
3		No	Go to the next step.
4	INSPECT HO2S HEATER POWER SUPPLY CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GROUND HO2S connector is disconnected. Turn the ignition switch to the ON position (Engine off). Measure the voltage between HO2S terminal C (wiring harness-side) and body ground. Is the voltage B+?	Yes	Go to the next step.
4		No	Inspect the HO2S heater power supply circuit related fuse. If the fuse is melt: Repair or replace the wiring harness for a possible short to ground. Replace the fuse. If the fuse is deterioration: Replace the fuse. If the fuse is normal: Repair or replace the wiring harness for a possible open circuit. Go to Step 9.
5	INSPECT HO2S HEATER Turn the ignition switch off. Inspect the HO2S heater. (See HEATED OXYGEN SENSOR (HO2S) INSPECTION ). Is there any malfunction?	Yes	Replace the HO2S, then go to Step 9. (See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION ).
5		No	Go to the next step.
6	INSPECT HO2S HEATER CONTROL CIRCUIT FOR SHORT TO GROUND HO2S connector is disconnected. Inspect for continuity between HO2S terminal D (wiring harness-side) and body ground. Is there continuity?	Yes	If the short to ground circuit could be detected: Repair or replace the wiring harness for a possible short to ground. If the short to ground circuit could not be detected: Replace the PCM (short to ground in PCM internal circuit). (See PCM REMOVAL/INSTALLATION ). Go to Step 9.
6		No	Go to the next step.
7	INSPECT PCM CONNECTOR AND TERMINALS Disconnect the PCM connector. Inspect for poor connection (such as damaged/pulled-out pins, and corrosion). Is there any malfunction?	Yes	Repair or replace the connector or terminals, then go to Step 9.
7		No	Go to the next step.
8	INSPECT HO2S HEATER CONTROL CIRCUIT FOR OPEN CIRCUIT HO2S and PCM connectors are disconnected. Inspect for continuity between HO2S terminal D (wiring harness-side) and PCM terminal 2BE (wiring harness-side). Is there continuity?	Yes	Go to the next step.
8		No	Repair or replace the wiring harness for a possible open circuit, then go to the next step.
9	VERIFY TROUBLESHOOTING OF DTC P0037 COMPLETED Make sure to reconnect all disconnected connectors. Clear the DTC from the PCM memory using the M-MDS. Perform the KOEO or KOER self test (using M-MDS) or Drive Mode 03 (PCM Adaptive Memory Production, EGR System, A/F Sensor Heater, HO2S Heater, A/F Sensor, HO2S, and TWC Repair Verification Drive Mode) (not using M-MDS). (See KOEO/KOER SELF TEST ). (See OBD-II DRIVE MODE ). Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION ).
9		No	Go to the next step.
10	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE ). Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE ).
10		No	DTC troubleshooting completed.