Mazda MX-6 1998, Workshop Manual

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TROUBLESHOOTING [ENGINE CONTROL FS]
STEP
INSPECTION ACTION
7
CHECK RESISTANCE OF HEATED OXYGEN
SENSOR GROUND CIRCUIT IN PCM
• Key off.
• PCM connected to breakout box. vehicle
harness disconnected from breakout box.
• Measure resistance between Test Pin 35
and Test Pin 91 at breakout box.
• Is resistance reading less than 5.0
ohms?
Yes REMOVE breakout box.
RECONNECT PCM.
Go to next step.
No REPLACE PCM.
REMOVE breakout box.
RECONNECT all components.
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
8 APPLY 12 VOLTS TO SUSPECT HEATED
OXYGEN SENSOR CIRCUIT
• Key off.
• Heated oxygen sensor (Rear)
disconnected.
• Jumper power to heated oxygen sensor
signal circuit at vehicle harness connector.
• Key on.
• Access heated oxygen sensor PID and
monitor.
• 02S 12 PID
• Is PID voltage greater than 1 .5 volts?
Yes REPLACE heated oxygen sensor.
RECONNECT all components.
RESET PCM to completely clear DTCs.
c r After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
No REPLACE PCM.
RECONNECT all components.
RESET PCM to completely clear DTCs.
tr After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
9 CHECK FOR OVER VOLTAGE ON HEATED
OXYGEN SENSOR CIRCUIT IN PCM
• Key on.
• PCM connected to vehicle harness.
• Heated oxygen sensor disconnected.
• Inspect both ends of connect for damaged
or pushed out pins, moisture, corrosion,
loose pins, etc. and service as necessary.
• Measure voltage between PCM ground
Test Pin at heated oxygen sensor vehicle
harness connector and battery negative
post.
• Measure voltage between heated oxygen
sensor signal Test Pin at heated oxygen
sensor vehicle harness connector and
battery negative post.
• Are voltage readings greater than 1.5
volts?
Yes REPLACE PCM.
RECONNECT all components.
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
No REPLACE heated oxygen sensor.
RECONNECT all components.
RESET PCM to completely clear DTCs.
o - After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
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