Dtc P0138 - Mazda 6 2002 Workshop Manual

STEP
6 INSPECT GAS LEAKAGE FROM EXHAUST
SYSTEM
• Visually check if any gas leakage is found
between ehaust manifold and front HO2S.
• Is there any gas leakage?
7 INSPECT SEALING OF ENGINE COOLANT
PASSAGE
Warning
• • • • Removing radiator cap when radiator is
hot is dangerous. Scalding coolant and
steam may shoot out and cause serious
injury.
• • • • When removing radiator cap, wrap a
thick cloth around and turn it slowly.
• Remove radiator cap.
• Implement procedure to bleed air from engine
coolant, then run engine at idle.
• Is there any small bubble, which makes engine
coolant white at filling opening?
Note
• Large bubbles are normal since they are
remaining air coming out from engine
coolant passage.
8 INSPECT ENGINE COMPRESSION
• Inspect engine compression.
(See B–9 COMPRESSION
• Is it okay?
9 VERIFY TROUBLESHOOTING OF DTC P0134
COMPLETED
• Make sure to reconnect all disconnected
connectors.
• Turn ignition key to ON (Engine OFF).
• Clear DTC from memory using WDS or
equivalent.
• Perform KOER self-test.
(See F–66 KOEO/KOER
• Is same DTC present?
10 VERIFY AFTER REPAIR PROCEDURE
• Perform “After Repair Procedure”.
(See F–66 AFTER REPAIR
• Is there any DTC present?
End Of Sie

DTC P0138

DTC P0138 Rear HO2S circuit high input
• PCM monitors input voltage from rear HO2S. If input voltage from rear HO2S sensor is above 0.45 V for 7
s during deceleration fuel cut, PCM determines that circuit input is high.
Diagnostic support note
• This is a continuous monitor (CCM).
DETECTION
• MIL illuminates if PCM detects the above malfunction condition in two consecutive drive cycles or in one
CONDITION
drive cycle while the DTC for the same malfunction has been stored in the PCM.
• PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
• FREEZE FRAME DATA is available.
• DTC is stored in the PCM memory.
POSSIBLE • Rear HO2S malfunction
CAUSE • Short to power circuit in wiring between rear HO2S terminal A and PCM terminal 1Y
F–112
ON-BOARD DIAGNOSTIC
INSPECTION
INSPECTION.)
SELF-TEST.)
PROCEDURE.)
Yes Repair or replace any faulty ehaust parts, then go to Step
9.
No • Inspect the following harnesses for open or short to
ground circuit, repair or replace harness if necessary
— Front HO2S terminal A (harness-side) to PCM
terminal 1AB (harness-side)
• Repair or replace harness if necessary.
• If all items above are okay, replace faulty sensor.
Then go to Step 9.
Yes Air gets in from poor sealing on head gasket or other areas
between combustion chamber and engine coolant
passage.
Repair or replace faulty parts, then go to Step 9.
No Go to net step.
Yes Go to net step.
No Implement engine overhaul for repairs, then go to net
step.
Yes Replace PCM, then go to net step.
(See F–43 PCM REMOVAL/INSTALLATION.)
No Go to net step.
Yes Go to applicable DTC troubleshooting.
(See F–67 DTC TABLE.)
No Troubleshooting completed.
ACTION
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