Oxygen sensor heat code
 

Got a code yesterday (sorry didn’t record the number) but my code reader said something to the effect “ o2 heater before cat on bank 2 insufficient heat.”

Had problems with my O2”s since the bank 1 sensor wire was mis-routed after head gasket repair and melted from too much exhaust manifold heat.

This likely the sensor or the circuit?


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Pre-heater for the O2 sensor and in 95% of the cases (or more) it's totally not a factor, ignore it.

I have the same code, although my air temps are a tad bit higher than most folks....

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What engine? So was the code only for that one sensor? (I was thinking about the common voltage source for lambda heating.)

Oxygen sensor heat code
 

3.0i engine. Only the one sensor.

Been fighting wandering codes including one that says the DISA is inactive. Have pulled it out and checked it and may be not functioning. Does not react to 12 v when I test it. Replacement doesn’t either so somewhat baffling.

Not all that concerned about the o2 heater but sort tired of the Check engine light coming on repeatedly.


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The DME will set a "heat" code if it doesn't see o2 voltage respond properly during the heat cycle which can have nothing to do with the heater itself. The DISA valve is vacuum actuated so powering the valve that controls the vacuum when there is no vacuum won't show anything.

I’ve tested the DISA after using a hand vacuum pump and according to YouTube the motor should shut the flap with vacuum applied. Doesn’t.
However, I bought a aftermarket DiSA and it did the same thing so maybe I’m doing something wrong in testing

I do suspect my DISA “not active” message is vacuum related. I have removed and resealed all of the intake connections in front of the manifold and am not finding any evidence of a vacuum leak. Still looking.


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Is the air pump working properly?

Doesn’t have air suspension if that’s what you are asking about.


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No, I mean the emissions air pump. It's located on the right fender. It feeds air into the exhaust manifold.

I seem to remember checking the DISA by manually moving the flap and putting my finger over the vacuum fitting to see if the diaphragm holds. The flap will close part way but should hold till you take your finger off. The solenoid must be normally open if I recall this correctly.

May have solved both problems although more work likely needed.

Discovered a 1-2 inch crack in the air filter housing box, covered it with duct tape.

Jiggled the connecting wires to bank 2 O2 sensor (these were butt connections previously repaired from heat damage). Will check for continuity and suspect connection later.

First startup the Check engine light never reappeared. 70 miles today, nothing.

A little surprised that the air filter box might create a vacuum leak but maybe I guess?


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Replies to others- I’ll check the air pump, I seem to recall there is a small vacuum line to it that I pulled loose while working on the O2 wiring once. Maybe again or compromised hose.

My DISA passes the simple “holds vacuum” test but there is another test that requires a vacuum being applied and injecting 12v to the connector causing the motor to activate and close the DISA flap. Mine failed that but so did a replacement DISA so good chance I did the test wrong.

Thanks to all for the help.


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If the first test works then applying power to the solenoid should let the flap open when closed(activated with vaccuum and no power.) Your DISA is likely fine.
Butt connectors are likely a big part of your problem.