MAZDA6 (3.0L)
WARNING: This page is about a different car, the 2003 Mazda Protege5, 2003 Mazda Protege, 2003 Mazda MX-5 Miata, 2003 Mazda MPV, and 2003 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
- Voltage Inspection
Warm engine to normal operating temperature. Disconnect HO2S 4-pin harness connector. Connect voltmeter between ground and HO2S 4-pin connector terminal "A". See Fig 1. Run engine at 3000 RPM until voltmeter indicates 0-1 volt. Ensure voltage changes within specification when engine RPM is increased or decreased several times. See HO2S VOLTAGE SPECIFICATIONS table. If voltage reading does not change as specified, replace suspect HO2S. If HO2S is okay but PID value is not as specified, go to next step. - Open Circuit Inspection
Disconnect PCM 104-pin harness connector. Check for continuity between following terminals:- Right front HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 60 (Yellow wire).
- Right front HO2S 4-pin harness connector terminal "B" and PCM 104-pin harness connector terminal No. 91 (Brown wire).
- Left front HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 87 (Green wire).
- Left front HO2S 4-pin harness connector terminal "B" and PCM 104-pin harness connector terminal No. 91 (Brown wire).
- Right rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 35 (White wire).
- Right rear HO2S 4-pin harness connector terminal "B" and PCM 104-pin harness connector terminal No. 91 (Brown wire).
- Left rear HO2S 4-pin harness connector terminal "A" and PCM 104-pin harness connector terminal No. 61 (Red wire).
- Left rear HO2S 4-pin harness connector terminal "B" and PCM 104-pin harness connector terminal No. 91 (Brown wire).
If continuity is present, go to next step. If continuity is not present, repair open circuit in suspect wire or replace wire harness. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS.
- Short Circuit Inspection
Check for continuity between following:- Right front HO2S 4-pin harness connector terminal "A" (Yellow wire) and power supply
- Right front HO2S 4-pin harness connector terminal "A" (Yellow wire) and ground.
- Right front HO2S 4-pin harness connector terminal "B" (Brown wire) and power supply.
- Left front HO2S 4-pin harness connector terminal "A" (Green wire) and power supply.
- Left front HO2S 4-pin harness connector terminal "A" (Green wire) and ground.
- Left front HO2S 4-pin harness connector terminal "B" (Brown wire) and power supply.
- Right rear HO2S 4-pin harness connector terminal "A" (White wire) and power supply.
- Right rear HO2S 4-pin harness connector terminal "A" (White wire) and ground.
- Right rear HO2S 4-pin harness connector terminal "B" (Brown wire) and power supply.
- Left rear HO2S 4-pin harness connector terminal "A" (Red wire) and power supply.
- Left rear HO2S 4-pin harness connector terminal "A" (Red wire) and ground.
- Left rear HO2S 4-pin harness connector terminal "B" (Brown wire) and power supply.
If continuity is present, repair short circuit in suspect wire or replace wire harness.
- HO2S Heater Resistance Inspection
Disconnect negative battery cable. Disconnect HO2S 4-pin harness connector. Using DVOM, measure resistance between HO2S 4-pin connector terminals "C" and "D". HO2S heater resistance reading should be 3.0-3.6 ohms (front HO2Ss) 5.0-7.0 ohms (rear HO2Ss). If HO2S heater is okay, but PID value is out of specification, check for open or short circuit. Go to next step. - Open Circuit Inspection
Disconnect PCM 104-pin harness connector. Check for continuity between following terminals:- Right front HO2S 4-pin harness connector terminal "C" and ignition relay (Blue/Black wire).
- Right front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 93 (White/Black wire).
- Left front HO2S 4-pin harness connector terminal "C" and ignition relay (Blue/Black wire).
- Left front HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness terminal 94 (White/Green wire).
- Right rear HO2S 4-pin harness connector terminal "C" and ignition relay (Blue/Black wire).
- Right rear HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 95 (Yellow/Green wire).
- Left rear HO2S 4-pin harness connector terminal "C" and ignition relay (Blue/Black wire).
- Left rear HO2S 4-pin harness connector terminal "D" and PCM 104-pin harness connector terminal No. 96 (Violet wire).
If continuity is present, go to next step. If continuity is not present, repair open circuit in suspect wire or replace wire harness. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS.
- Short Circuit Inspection
Check for continuity between following:- Right front HO2S 4-pin harness connector terminal "C" (Blue/Black wire) and body GND.
- Right front HO2S 4-pin harness connector terminal "D" (Violet wire) and power supply.
- Right front HO2S 4-pin harness connector terminal "D" (Violet wire) and body GND.
- Left front HO2S 4-pin harness connector terminal "C" (Blue/Black wire) and body GND.
- Left front HO2S 4-pin harness connector terminal "D" (Violet wire) and power supply.
- Left front HO2S 4-pin harness connector terminal "D" (Violet wire) and body GND.
- Right rear HO2S 4-pin harness connector terminal "C" (Blue/Black wire) and body GND.
- Right rear HO2S 4-pin harness connector terminal "D" (Violet wire) and power supply.
- Right rear HO2S 4-pin harness connector terminal "D" (Violet wire) and body GND.
- Left rear HO2S 4-pin harness connector terminal "C" (Blue/Black wire) and body GND.
- Left rear HO2S 4-pin harness connector terminal "D" (Violet wire) and power supply.
- Left rear HO2S 4-pin harness connector terminal "D" (Violet wire) and body GND.
If continuity is present, repair short circuit in suspect wire or replace wire harness.