QUESTION & ANSWER: 02 sensor’s not a problem on CX-5

Q: We have a 2014 Mazda CX-5 and a check-engine light is on. We took it to Mazda and their formula reader pronounced it was an 02 sensor. We had them reinstate a sensor 3 times and a light is still on. Any thoughts?


A: Even yet a formula is for an O2 (oxygen) sensor, it is flattering apparent a problem isn’t with a sensor itself. There are 3 probable forms of faults that can means O2 sensor codes.

One is with a wiring between a sensor and a engine computer, another is with a involuntary operation of a engine and a other is with a empty complement itself.

The O2 sensor is a “monitor” of a fuel injection system. It is a usually sensor that reads a opening of a explosion routine and tells a mechanism either a empty gases are too gaunt or too rich.

During operation it sends a non-static voltage vigilance behind to a engine mechanism that has really small current. If there is any insurgency in a electrical connections, afterwards a vigilance is interfered with and a formula might set.

The insurgency could be during a connector for a O2 sensor or it might be where a wiring strap plugs into a engine computer. It could also be inner in a engine mechanism nonetheless this is rare.

A clever visible investigation of a electrical connectors might not uncover anything though try regulating a gangling electrical depot to do a “drag” exam for involuntary hit on any of a connectors and we might find a problem.

Also, check a belligerent tie between a physique and a engine. This can means problems that are formidable to diagnose.

A involuntary problem with a engine, including hint block misfiring, can set O2 sensor codes since a air/fuel reduction is not burnt completely, though this would typically set other codes as well, so we consider we can order this out.

Finally, an atmosphere trickle in a empty complement can means O2 codes to set. The trickle would be before a O2 sensor in a empty complement and might not means any sound though still concede atmosphere into a empty system.

A clever investigation of a empty plural and pipes should locate this form of fault.

Often, when a formula is set in any fuel injection system, a problem isn’t with a sensor or device though rather with something else that affects that sensor.

This is a box in your car though a problem can be found nonetheless it might take a small time.

Q: we have a 2009 Ford Edge with all-wheel drive. we don’t have any problems with my Edge though my crony has a identical Edge and a send box that bolts to a delivery failed. The automechanic he took it to transposed a send box with a new section and told him failures were common. What we would like to know is, if a automechanic is right, is there any approach to lengthen a life of a all-wheel-drive send box in my Edge so we don’t have to commence costly replacement?


A: I have seen a series of failures of these send box gearboxes in comparison Edge all circle expostulate models and when they destroy it is formidable to tell what caused a failure.

Was it a bearing, H2O in a oil, or a error with a gears? By a time a sound starts, there are problems with all a parts, so deputy of a section is a usually possibly repair.

To lengthen a life of a unit, we would suggest unchanging oil changes for a send box unit. The upkeep primer doesn’t list oil deputy intervals though depending on a pushing conditions, we would suggest as brief as 30,000 km for oil changes.

The slipperier a highway conditions, a some-more a AWD section has to work, so oil changes are some-more important.

Older Edge models didn’t have an oil empty block on a send case, so a suction gun can be used to siphon a aged oil out and put new oil into a unit.

The gearbox doesn’t reason most oil and uses MERCON LV form oil.

Do not brew this with MERCON IV liquid used in involuntary transmissions in other models.

Jim Kerr is a master vehicle automechanic and teaches automotive technology. Send your questions for Jim to or mail them to: Herald Wheels, 2717 Joseph Howe Drive, P.O. Box 610, Halifax, N.S. B3J 2T2

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