Protege & Protege5
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. Allow engine to idle. Disconnect HO2S 4-pin harness connectors (front or rear). Connect analog voltmeter test leads to HO2S 4-pin connector terminals "A" and "B". Increase engine RPM to 3000 until voltmeter reads about 0.5-0.7 volt. Ensure voltmeter needle moves while increasing or decreasing engine speed suddenly several times. See HO2S VOLTAGE SPECIFICATIONS table. If voltmeter needle moves, but PID value or PCM terminal No. 60 (front HO2S) or No. 35 (rear HO2S) voltage readings are out of specification, check for open or short circuit between PCM and HO2S. Go to next step. If voltmeter needle does not move with engine speed, replace HO2S. - Open Circuit Inspection
Connect 104-Pin Breakout Box (49-UN01-130) between PCM and harness connector. See Figure. Check for continuity between following terminals:- HO2S 4-pin harness connector terminal "A" (Yellow/Blue wire) and breakout box terminal No. 35 (rear sensor).
- HO2S 4-pin harness connector terminal "A" (Pink/Blue wire) and breakout box terminal No. 60 (front sensor).
- HO2S 4-pin harness connector terminal "B" (Orange wire) and breakout box terminal No. 91.
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 HO2S 4-pin harness connector terminal "A" and breakout box terminal No. 60 (front sensor) or No. 35 (rear sensor) to ground. If continuity is present, repair wiring or replace wire harness as necessary. If continuity is not present, go to next step. - HO2S Heater Resistance Inspection
Allow sensor to cool to room temperature. Disconnect front or rear HO2S 4-pin harness connector. Measure resistance between front HO2S 4-pin connector terminals "C" and "D". See Figure. Resistance reading should be about 5.6 ohms at 68°F (20°C). Measure resistance between rear HO2S 4-pin connector terminals "C" and "D". See Figure. Resistance reading should be about 15.7 ohms. If resistance reading is not as specified, replace appropriate HO2S. If resistance reading is as specified but PID value or PCM terminal No. 93 or 94 voltage is out of specification, check for open or short circuit. Go to next step. - Open Circuit Inspection
Connect 104-Pin Breakout Box (49-UN01-130) between PCM and PCM 104-pin harness connector. See Figure. Check for continuity between following terminals:- HO2S 4-pin harness connector terminal "C" and ignition switch terminal "IG1" (Blue wire) through common connector. See Fig 1.
- HO2S 4-pin harness connector terminal "D" (Green/Red wire) and breakout box terminal No. 93 (rear sensor).
- HO2S 4-pin harness connector terminal "D" (Light Green/Red wire) and breakout box terminal No. 94 (front sensor).
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 ground and following circuits:- HO2S 4-pin harness connector terminal "C" and ignition switch terminal "IG1" (Blue wire) through common connector to ground. See Fig 1.
- HO2S 4-pin harness connector terminal "D" (Green/Red wire) and breakout box terminal No. 93 (rear sensor) to ground.
- HO2S 4-pin harness connector terminal "D" (Light Green/Red wire) and breakout box terminal No. 94 (front sensor) to ground.
If continuity is present, repair or replace wire harness as necessary. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. If short circuit is not present, replace suspect HO2S.