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Home >> Mazda >> 2021 >> CX-9 Touring, AWD >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic - Engine Control System (1 Of 6) >> DTC P0037-00: Ho2S Heater Control Circuit Low Input >> Diagnostic Procedure
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Diagnostic Procedure

DTC P0037:00 DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 RECORD FREEZE FRAME DATA/SNAPSHOT DATA AND DIAGNOSTIC MONITORING TEST RESULTS TO UTILIZE WITH REPEATABILITY VERIFICATION
NOTE:
  • Recording can be facilitated using the screen capture function of the PC.
  • Record the FREEZE FRAME DATA/snapshot data and DIAGNOSTIC MONITORING TEST RESULTS (A/F sensor heater, HO2S heater related) on the repair order.
- Go to the next step.
2 VERIFY RELATED REPAIR INFORMATION AVAILABILITY
  • 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 INSPECT HO2S CONNECTOR CONDITION
  • Switch the ignition off.
  • Disconnect the HO2S connector.
  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
  • Is there any malfunction?
Yes Repair or replace the connector and/or terminals, then go to Step 9.
No Go to the next step.
4 INSPECT HO2S HEATER POWER SUPPLY CIRCUIT FOR SHORT TO GROUND OR OPEN CIRCUIT
  • Verify that the HO2S connector is disconnected.
  • Switch the ignition ON (engine off).
    NOTE:
    • Another DTC may be stored by the PCM detecting an open circuit.
  • Measure the voltage at the HO2S terminal C (wiring harness-side).
  • Is the voltage B+?
Yes Go to the next step.
No Inspect the ENGINE 1 15 A fuse.
  • If the fuse is blown:
    • Refer to appropriate wiring diagram and verify whether or not there is a common connector between ENGINE 1 15 A fuse and HO2S terminal C.

If there is a common connector:
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
  • Repair or replace the malfunctioning part.

If there is no common connector:
  • Repair or replace the wiring harness which has a short to ground.
    • Replace the fuse.
    • If the fuse is damaged:
      • Replace the fuse.
  • If the fuse is normal:
    • Refer to appropriate wiring diagram and verify whether or not there is a common connector between main relay terminal C and HO2S terminal C.

If there is a common connector:
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
    • Repair or replace the malfunctioning part.

If there is no common connector:
  • Repair or replace the wiring harness which has an open circuit.

Go to Step 9.
5 INSPECT HO2S HEATER
Yes Replace the HO2S, then go to Step 9.
(See HEATED OXYGEN SENSOR (HO2S) REMOVAL/INSTALLATION [SKYACTIV-G 2.5T] .)
No Go to the next step.
6 INSPECT PCM CONNECTOR CONDITION
  • Switch the ignition off.
  • Disconnect the PCM connector.
  • Inspect for poor connection (such as damaged/pulled-out pins, corrosion).
  • Is there any malfunction?
Yes Repair or replace the connector and/or terminals, then go to Step 9.
No Go to the next step.
7 INSPECT HO2S HEATER CONTROL CIRCUIT FOR OPEN CIRCUIT
  • Verify that the HO2S and PCM connectors are disconnected.
  • Inspect for continuity between HO2S terminal D (wiring harness-side) and PCM terminal 2C (wiring harness-side).
  • Is there continuity?
Yes Go to the next step.
No Refer to appropriate wiring diagram and verify whether or not there is a common connector between HO2S terminal D and PCM terminal 2C.
If there is a common connector:
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
  • Repair or replace the malfunctioning part.

If there is no common connector:
  • Repair or replace the wiring harness which has an open circuit.

Go to Step 9.
8 INSPECT HO2S HEATER CONTROL CIRCUIT FOR SHORT TO GROUND
  • Verify that the HO2S and PCM connectors are disconnected.
  • Inspect for continuity between HO2S terminal D (wiring harness-side) and body ground.
  • Is there continuity?
Yes Refer to appropriate wiring diagram and verify whether or not there is a common connector between HO2S terminal D and PCM terminal 2C.
If there is a common connector:
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
  • Repair or replace the malfunctioning part.

If there is no common connector:
  • Repair or replace the wiring harness which has a short to ground.

Go to the next step.
No Go to the next step.
9 VERIFY DTC TROUBLESHOOTING COMPLETED
Yes Repeat the inspection from Step 1.

Go to the next step.
No Go to the next step.
10 VERIFY AFTER REPAIR PROCEDURE
Yes Go to the applicable DTC inspection.
(See DTC TABLE [PCM (SKYACTIV-G 2.5T)] .)
No DTC troubleshooting completed.