626 2.5L (Using Breakout Box)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2002 Mazda Protege5, 2002 Mazda Protege, 2002 Mazda Millenia, 2002 Mazda MX-5 Miata, and 2002 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.

Warm engine to normal operating temperature. Turn ignition switch off. Connect 104-Pin Breakout Box (49-UN01-130) between PCM and PCM harness connector. See Figure .

Voltage Inspection

Turn ignition switch on. Measure voltage at PCM terminal No. 35 (right rear HO2S), 60 (right front HO2S), 61 (left rear HO2S) or 87 (left front HO2S). See HO2S VOLTAGE (626 2.5L) table. If voltage is not as specified, check wiring harness and connectors between PCM and HO2S. Also check intake-air system, fuel system and self-diagnostic system. Repair as necessary. If system or wiring harness problems are not present, replace HO2S.

HO2S Heater Resistance Inspection

Disconnect HO2S 4-pin connector. Using ohmmeter, measure resistance between HO2S 4-pin connector terminals "C" and "D". See Fig 1 . See HO2S HEATER RESISTANCE SPECIFICATION (626 2.5L) table. If resistance is not as specified, replace HO2S. If resistance readings are within specification, check related wiring harness and connectors.

HO2S VOLTAGE (626 2.5L)

Application			Volts
Right Front HO2S
Ignition On			Less Than 1.0
Acceleration			0.5-1.0
Deceleration			0-0.5
Idle
After Warm Up			0.1-0.9
Engine Cold			Less Than 0.5
Left Front HO2S
Ignition On			Less Than 1.0
Acceleration			0.5-1.0
Deceleration			0-0.5
Idle
After Warm Up			0.1-0.9
Engine Cold			Less Than 0.5
Right Rear HO2S
Ignition On			Less Than 1.0
Acceleration			About 0
Deceleration			About 0
Idle
After Warm Up			0.1-0.9
Engine Cold			About 0
Left Rear HO2S
Ignition On			Less Than 1.0
Acceleration			About 0
Deceleration			About 0
Idle
After Warm Up			0.1-0.9
Engine Cold			About 0

Fig 1: Identifying HO2S Connector Terminals - Terminal Views (626 2.5L)

Courtesy of MAZDA MOTORS CORP.