Mazda 6 2002 Workshop Manual page 172

DTC P0031 Front HO2S heater circuit low input
Diagnostic procedure
STEP
1 PERFORM DTC CONFIRMATION PROCEDURE
• Perform DTC CONFIRMATION PROCEDURE.
(See F–66 DTC CONFIRMATION
PROCEDURE.)
• Is same DTC present?
2 INSPECT POOR CONNECTION OF FRONT
HO2S CONNECTOR
• Turn ignition key to OFF.
• Disconnect front HO2S connector.
• Inspect for poor connection (damaged, pulled-
out pins, corrosion, etc.).
• Are there any malfunctions?
3 INSPECT FRONT HO2S HEATER
• Inspect front HO2S heater.
(See F–56 HEATED OXYGEN SENSOR
(HO2S) INSPECTION.)
• Is front HO2S heater okay?
4 INSPECT POWER CIRCUIT OF FRONT HO2S
HEATER FOR OPEN CIRCUIT
• Turn ignition key to ON (Engine OFF).
• Measure voltage between front HO2S terminal
C (harness-side) and body ground.
• Is voltage B+?
5 INSPECT POOR CONNECTION OF PCM
CONNECTOR
• Turn ignition key to OFF.
• Disconnect PCM connector.
• Inspect for poor connection (damaged, pulled-
out pins, corrosion, etc.).
• Are there any malfunctions?
ON-BOARD DIAGNOSTIC
INSPECTION
Yes Go to net step.
No Intermittent concern eists. Go to INTERMITTENT
CONCERN TROUBLESHOOTING procedure.
(See F–227 INTERMITTENT CONCERN
TROUBLESHOOTING.)
Yes Repair or replace terminal, then go to Step 8.
No Go to net step.
Yes Go to net step.
No Replace front HO2S, then go to Step 8.
Yes Go to net step.
No Repair or replace harness for open circuit, then go to Step
8.
Yes Repair terminal, then go to Step 8.
No Go to net step.
ACTION
F–75
F