DTC P0037

Rear HO2S heater circuit low input

DETECTION CONDITION

• The PCM monitors the rear HO2S heater control voltage when the PCM turns the rear HO2S heater on. If the control voltage is less than 57% of the battery voltage, the PCM determines that the rear HO2S heater control circuit voltage is low.

Diagnostic support note

• This is a continuous monitor (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 is available.

• The DTC is stored in the PCM memory.

POSSIBLE CAUSE

• Rear HO2S heater malfunction

• Connector or terminal malfunction

• Open circuit in wiring harness between ignition relay and rear HO2S terminal C

• Short to ground in wiring harness between ignition relay and rear HO2S terminal C

• Open circuit in wiring harness between rear HO2S terminal D and PCM terminal 2BE

• Short to ground in wiring harness between rear HO2S terminal D and PCM terminal 2BE

• PCM malfunction

STEP

INSPECTION

ACTION

1

• Have FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (HO2S heater related) been recorded?

Yes

Go to the next step.

No

Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.

2

• Verify related Service Bulletins and/or on-line repair information availability.

• Is any related repair information available?

Yes

Perform repair or diagnosis according to the available repair information.

• If the vehicle is not repaired, go to the next step.

No

Go to the next step.

3

• Turn the ignition switch off.

• Disconnect the rear HO2S connector.

• Inspect for poor connection (such as damaged/pulled-out pins, and corrosion).

• Is there any malfunction?

Yes

Repair or replace the terminal, then go to Step 9.

No

Go to the next step.

4

• Turn the ignition switch to the ON position (Engine off).

• Measure the voltage between rear HO2S terminal C (wiring harness-side) and body ground.

• Is the voltage B+?

Yes

Go to the next step.

No

Repair or replace the wiring harness for a possible open circuit or short to ground, then go to Step 9.

5

• Turn the ignition switch off.

• Inspect for continuity between rear HO2S terminal D (wiring harness-side) and body ground.

• Is there continuity?

Yes

Repair or replace the wiring harness for a possible short to ground, then go to Step 9.

No

Go to the next step.

6

• Turn the ignition switch off.

• Inspect for continuity between rear HO2S terminal D (wiring harness-side) and PCM terminal 2BE (wiring harness-side).

• Is there continuity?

Yes

Go to the next step.

No

Repair or replace the wiring harness for a possible open circuit, then go to Step 9.

7

• Turn the ignition switch off.

• 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 terminal, then go to Step 9.

No

Go to the next step.

8

• Inspect the rear HO2S heater.

  (See REAR HEATED OXYGEN SENSOR (HO2S) INSPECTION [LF].)

• Is there any malfunction?

Yes

Replace the rear HO2S, then go to the next step.

(See REAR HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

9

• Make sure to reconnect all disconnected connectors.

• Clear the DTC from the PCM memory using the M-MDS.

• Perform the KOEO self-test (using M-MDS) or the HO2S heater, HO2S, and TWC Repair Verification Drive Mode (not using M-MDS).

  (See KOEO/KOER SELF TEST [LF].)

  (See OBD-II DRIVE MODE [LF].)

• Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF].)

No

Go to the next step.

10

• Perform the “AFTER REPAIR PROCEDURE”.

  (See AFTER REPAIR PROCEDURE [LF].)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [LF].)

No

DTC troubleshooting completed.