ThunderMax Oxygen (O2) Sensor Operation Testing - Manual (Page 2)

AFR value is constantly 22.05 on “both cylinders”.
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O2 sensors NOT plugged in.

O2 module not connected to DATA PLUG properly.
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O2 module DATA PLUG not receiving 12V power.

Accessory fuse blown or corroded.
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O2 module Faulty
AFR values (any value) always EXACTLY the same on “both cylinders”.

O2 sensors NOT plugged in.

O2 module not connected to DATA PLUG properly.

O2 module DATA PLUG not receiving 12V power.

Accessory fuse blown or corroded.
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O2 module Faulty
AFR value varies less than 0.5 (Example: 14.20 – 14.70) when throttle is twisted and released.

O2 sensor faulty
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O2 sensor wiring damaged
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Factory OEM sensors are PLUGGED IN
AFR value periodically indicates 19.36 or 22.05 on one cylinder.

O2 sensor plugs NOT securely SNAPPED together
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O2 sensor harness plug wires pulled from plug. (Firmly pull on EACH wire at the connector)
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O2 sensor faulty
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O2 sensor connection broken
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O2 sensor wire damaged (Melted by exhaust, rubbed through by drive belt, abrasion damage)
AFR value for ONE cylinder reads LEAN (AFR = 16.00 or greater always but engine idles good)

Exhaust gasket leak.
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Weld at O2 sensor leaking (Use Soapy Water test to determine)

Crack in affected cylinder’s exhaust pipe