Mazda 6 2002 Workshop Manual page 210

DTC P0138 Rear HO2S circuit high input
Diagnostic procedure
STEP
1 VERIFY FREEZE FRAME DATA HAS BEEN
RECORDED
• Has FREEZE FRAME DATA been recorded?
2 VERIFY RELATED SERVICE INFORMATION
AVAILABILITY
• Check for related Service Information
availability.
• Is any related Service Information available?
3 VERIFY RELATED PENDING OR STORED
DTCS
• Turn ignition key to OFF, then ON (Engine
OFF).
• Verify pending code or stored DTCs using
WDS or equivalent.
• Is other DTC present?
4 IDENTIFY TRIGGER DTC FOR FREEZE FRAME
DATA
• Is DTC P0138 on FREEZE FRAME DATA?
5 INSPECT REAR HO2S SIGNAL CIRCUIT FOR
SHORT TO POWER SUPPLY CIRCUIT
• Turn ignition key to OFF.
• Disconnect rear HO2S connector.
• Turn ignition key to ON (Engine OFF).
• Measure voltage between rear HO2S terminal
A (harness-side) and body ground.
• Is any voltage reading?
6 VERIFY CURRENT INPUT SIGNAL STATUS
• Start engine.
• Access O2S12 PID using WDS or equivalent.
• Verify PID while racing engine at least 10
times (in NEUTRAL (MTX) or PARK (ATX)).
• Does PID reading stay above 0.45 V?
ON-BOARD DIAGNOSTIC
INSPECTION
Yes Go to net step.
No Record FREEZE FRAME DATA on repair order, then go to
net step.
Yes Perform repair or diagnosis according to available Service
Information.
• If vehicle is not repaired, go to net step.
No Go to net step.
Yes Go to appropriate DTC troubleshooting procedures.
(See F–67 DTC TABLE.)
No Go to net step.
Yes Go to net step.
No Go to troubleshooting procedures for DTC on FREEZE
FRAME DATA.
(See F–67 DTC TABLE.)
Yes Replace short to power supply circuit, then go to Step 7.
No Go to net step.
Yes Repair or replace sensor, then go to net step.
No Go to net step.
ACTION
F–113
F