2009 Buick Enclave blowing emission 2 fuse

recently bought a 2009 Enclave CXL AWD. I had to spend $4,500 fixing various engine issues such as timing chain + rack and pinion. Now, I’m facing 8 engine codes related to cooling fan relays and O2 sensor heating circuits. I found that the problem is linked to the emission 2 fuse, which controls these components. I replaced the blown fuse twice, but it keeps blowing. Any suggestions on how to fix this or get to the bottom of the problem?

I would look at something in the circuit that could draw more current than normal with use/age.

Which would be the cooling fan motors.



Ask your shop if there’s a spec on the engine compartment cooling fan’s max current draw. If so, they’d be able to compare yours to the spec. If the fan motors test ok to spec, have to look elsewhere. It’s sort of unusual the cooling fan and the o2 sensor heaters would be on the same circuit, but such a thing is possible I guess.

Edit: Given Nevada’s info below, unlikely to be the cooling fan’s motor. More likely a faulty o2 sensor or its wiring. If I had that problem I’d measure each o2 sensor’s the heater resistance and compare to the spec, probably in the 15 ohm range, about 10 watts.

That fuse supplies power to the downstream oxygen sensor heaters, you can temporarily unplug one or both sensors to see if the short circuit stops occurring.

That fuse also powers the cooling fan relays and compressor clutch relay. It only powers the coil side of the relays, that fuse does not power the fans or compressor clutch, so the problem is unlikely to be in the cooling fan circuit.

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Thanks for the response, I should have also added that the car has overheated 1 time in the 2 months that I’ve owned it. I am just not so sure that it could be the o2 sensors, as the previous owner had them all replaced and the mechanic that did my 4000 in repairs also replaced one of the sensors.

The fan relays won’t operate if that fuse is blown.

There are 4 oxygen sensors, were they all replaced?

The previous owner had replaced all 4. My mechanic replaced 1. I don’t see why they’d be going bad so fast.

There could be chafing in the wiring harness going to the sensors. The wiring harness should be inspected for damage.

Was this car involved in a flood? Maybe have a salvage title?

It just seems to have a lot of weird problems…

It was not in a flood and the title is clean. After finally getting it on a real lift I was able to spot a pinched wire. The previous owner had removed the cats probably to sell it, and when putting the wiring back he put it in a pinch point for the exhaust so bare wire is now exposed. Me and my mechanic suspect this as the problem for the fuse blowing.


The previous owner removed catalysts to sell the car? Did you buy it in that condition?

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Were the old cats replaced with new ones? In any event, the bare wire you found seems a likely suspect.

yes i bought it like this, definitely regret it this car has been a pain since day 1. did not know he removed the cats until now

no the cats were not replaced. the exhaust has a pipe welded on in place of them. after replacing the bare wire and moving it to a safer location a lot of my codes have went away, besides a couple of them involving o2 sensor heaters in bank 2. shortly after fixing this it now has misfires even after replacing the spark plugs and ignition coils. I suspect the valve cover gasket is allowing oil to leak


The first code is saying you have a misfire on cylinder 1. The next two are about problems with the o2 sensor system. Those may be the cause of the first code. The correct air/fuel mixture depends on the o2 sensor system, and either too lean or too rich of mixture can cause a misfire. I expect you’ll need to install new cats in order to have a chance at solving the o2 sensor issues and the misfire. You might ask your shop do a fuel-trim measurement, might provide some evidence of an air/fuel problem.

Try swapping the fuel injector from cylinder #1 with another from a different cylinder to see if the miss moves with the injector.

The P0161 code is for the heater circuit for the downstream O2 Sensor.

The P0050 code is for the heater circuit for one of the upstream O2 sensors.

Neither of these would cause a misfire in cylinder #1.


It didn’t misfire for the first 8 months of owning it with these codes. when taking the plug out to inspect it they were coated in oil and the old plugs have very bad carbon buildup

Is the oil on the porcelain part of the plug (above where it screws in), or on the firing tip, the gap? Carbon buildup at the firing tip is often a symptom of a too-rich mixture. Was one of the plugs worse-looking than the others?

the gap and all along the threads

So there’s no oil on the top part of the spark plugs above where they screw in? The oil is only appearing on the threads and on the firing tip? If so, you may have bigger problems than just the missing cats and o2 sensors. Could be the pistons are not sealing correctly to the cylinder walls, or the oil pressure is too high. Ask your shop if a compression and oil pressure test might be a helpful next step. If you posted photos of your old plugs, folks here might be able to offer up some more ideas. .How much oil are your using, in quarts per 1000 miles? Do you notice any blue-ish smoke coming out of the tailpipe?