Mazda MX-6 1998, Workshop Manual

Page: 60 / 1282

TROUBLESHOOTING [ENGINE CONTROL FS]
STEP INSPECTION
ACTION
4
CHECK HEATED OXYGEN SENSOR
HARNESS CIRCUIT FOR SHORT TO
POWER AND GROUND AND PCM GROUND
(BETWEEN PCM AND H 02S GROUND
CIRCUIT)
• Key off.
• Disconnect NGS tester from DLC.
• Disconnect PCM. Inspect both ends of
connector for damaged or pushed out pins,
moisture, corrosion and loose pins. Service
as necessary.
• Breakout box installed. Leave PCM
disconnected.
• Disconnect suspected heated oxygen
sensor.
• Measure resistance between heated
oxygen sensor signal Test Pin and PCM
ground Test Pin at breakout box.
• Measure resistance between heated
oxygen sensor signal Test Pin and power
and constant voltage Test Pin at breakout
box.
• Measure resistance between heated
oxygen sensor signal Test Pin and ground
Test Pin at breakout box.
• Heated oxygen sensor (Rear)=Test Pin
35
• PCM ground=Test Pin 91
• Ground=Test Pins 24 and 103
• Power=Test Pin 71 and 97
• Constant voltage=Test Pin 90
• Is resistance greater than 10,000 ohms?
Yes Go to next step.
No SERVICE short circuit in harness.
REMOVE breakout box.
RECONNECT all components.
RESET PCM to completely clear DTCs.
o ’ After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
5 CHECK RESISTANCE OF HEATED OXYGEN
SENSOR AND HEATED OXYGEN SENSOR
GROUND CIRCUIT
• Key off.
• Breakout box installed. PCM disconnected.
• Disconnect suspected heated oxygen
sensor.
• Measure resistance between heated
oxygen sensor signal Test Pin at breakout
box and heated oxygen sensor vehicle
harness connector. Record readings.
• Measure resistance between PCM ground
Test Pin at breakout box and heated
oxygen sensor PCM ground vehicle
harness connector. Record readings.
• Heated oxygen sensor (Rear)=Test Pin
35
• PCM ground=Test Pin 91
• Is resistance reading less than 5.0
ohms?
Yes Go to next step.
No SERVICE open circuit in harness.
REMOVE breakout box.
RECONNECT all components.
RESET PCM to completely clear DTCs.
ft
After Repair Procedure
COMPLETE OBD II Drive Mode.
RERUN OBD Test.
6 CHECK HEATED OXYGEN SENSOR
CIRCUIT RESISTANCE
• Key off.
• PCM connected to vehicle harness.
• Connect suspected heated oxygen sensor
connector.
• NGS tester connected.
• Key on, engine off.
• Access correct heated oxygen sensor PID.
• 0 2 S 1 2 P ID
Note
• Heated oxygen sensor displayed as
0 2 S 1 2 (Rear) on NGS tester.
• Heated oxygen sensor (Rear)=Test Pin
35
• Is voltage greater than 1.5 volts?
Yes
Go to step 9.
No Go to next step.
0 1 -0 1 A -3 2