losiglow

iTrader: (1)

This method of eliminating the P0420 or P0430 code applies to just about any car with a gasoline engine and a 4-wire downstream O2 sensor. The P0430 applies only to engines with a 2nd bank like a V6 or V8. The only purpose of the downstream O2 sensor is to make sure the exhaust doesn't contain excessive pollutants. The description of the code is "Catalyst Efficiency Below Threshold" which essentially means your cat isn't working as well as it should. However, It can also result from a malfunctioning engine, so it's not something you should immediately assume is due to the catalytic converter. If your air/fuel ratio is goofed up due to other malfunctioning sensors, or the engine is consuming a lot of oil or coolant due to bad piston rings or a head gasket problem, it's going to cause excessive emissions which can throw the code. So if you're seeing other codes, especially ones that indicate other sensors, you'll want to fix those first. This fix is assuming you only have the one code, not multiple, which could indicate a bigger problem. Also, this ONLY applies to the downstream O2 sensor. The upstream sensor that is usually located immediately after the exhaust manifold but before the catalytic converter substrate is an Air/Fuel ratio sensor. Don't make the mistake of messing with with that one. The upstream and downstream look very similar but the upstream usually has 5 or 6 wires. The downstream has 4.

I've had a chronic P0430 code over the last year or so. I believe it's from damage to the catalytic converter due to a pretty severe oil burning issue I had a while back on one of the cylinders. The original factory sensor was replaced due to the consistent code but it made no difference. Which leads me to believe it's the cat. The oil consumption issue is fixed but the damage is likely already done on the cat attached to Bank 2. The cylinder liner for that #5 was damaged which resulted in oil consumption of about 1 qt. every 200-300 miles, which exposed the cat to a lot of oil contaminated exhaust, which can coat the substrate as well as heat it up well beyond it's designed heat range causing permanent damage. I've also attempted to clean the cat using various methods but to no avail.

I was still able to pass emissions though (after resetting the codes ), which includes a sniffer test. The sniffer test detects unburned hydrocarbons and CO levels. The car easily passes the sniffer test which tells me that the cat is working well enough but that the ECU just isn't happy with the emissions. Apparently Acura has higher standards than the state. I include that little detail because I'm a hippy at heart and don't condone hacking a car's emission control systems. I might consider replacing the cat if the car was putting out HC/CO high levels. But it's not.

I first tried the spark plug extender trick, which places the O2 sensor further from the exhaust path. Sort of like the defoulers on the pre-cat deletes you can get from RV6. That resulted in the code popping up less frequently, but not eliminating it altogether.

There are two main reasons the O2 sensor will result in these codes
1. The voltage is above 1V. The voltage should stay within 0.0V - 0.9V. Excessive emissions can result it going into the 1V or higher range.
2. The voltage levels fluctuate excessively which indicates an inefficient catalytic converter. The voltage level should be relatively steady when the throttle is consistent. The voltage levels will fluctuate based on throttle but shouldn't be all over the place when the throttle is consistent. For example, cruising on the highway.

In my case, the problem was due to the latter - excessive fluctuations in the voltage level. I only have a screen shot of post-"fix" but imagine the peaks and valleys of the graph being about 5X steeper. So instead of fluctuating from about 0.6V-0.7V like below, having peaks and valleys fluctuating from 0.2V to 0.9V.




Sort of like this:


I should also mention, I'm quite certain the cause of the fluctuations wasn't engine related. If it were, it's likely I'd see some goofy fuel trim numbers. When the engine was burning oil, the long-term fuel trim (LTFT) was as "high" as -15, which indicates an excessively rich mixture - presumably from so much oil in the exhaust. Now, values are almost identical between the two banks and almost always between -3 and +3 (top gauges).



The code, P0430, would usually surface within 50 miles. I was able to get it to about 100 miles before the code when I installed the spark plug extender but almost never more than that.



Sometimes it would be a "pending" fault, indicating that the ECU sees the fault but is giving it a bit of time before it triggers the CEL. More often, several miles after pending, it would be an "active" fault at which point the ECU confirmed it's a consistent fault and would trigger the CEL.

Now, 650 miles after the fix:



The "fix" described below:

losiglow

iTrader: (1)

The "fix" is essentially installing a low pass filter into the O2 sensor wiring. There are several places on the interwebz including YouTube that contains instructions for this. However, I found some of them to be vague or confusing and none of them were specific to the wire colors on the TL's O2 sensors. It's important to wire things up correctly otherwise it won't work.

If you have the OEM sensor, which is a Denso, the wiring will be as follows:


If you have a generic O2 sensor, it will be different:



That's for pretty much any Honda or Acura. For other vehicles - you'll want to find the diagram for your specific sensor. You can usually find this by googling "downstream O2 sensor wiring color diagram" or something like that.

BTW, generic O2 sensors are usually OK to use for the downstream O2, and are a lot less expensive than OEM. For the upstream O2, I'd only use OEM since it measures air/fuel ratios. Precise measurement of the A/F ratio is critical so half-assing it is a no-no. But the downstream is relatively universal among most vehicles and doesn't affect vehicle performance in any way. I've used generic downstream sensors for a few vehicles and have never had problems. Until now that is. But I don't think this problem is sensor related because the code was there before.

You'll need the following components:

- 1000 ohm (1K) 1/4 watt (0.25W) resistor


- 1uF - 250V capacitor



You can find these on eBay for cheap. I paid $3 for 20 resistors and $5 for 10 capacitors. They often come bulk so finding just 1 for sale isn't usually an option. I'm not an expert on electronic circuitry but based on what's being accomplished here, you could probably use components that have different specs with similar results. Using a 100ohm resistor may accomplish the same task but might result slightly steeper peaks/valleys than a 1K ohm. And using a larger capacitor is always fine since it simply has a larger capacity. These specs just seem to be the most common among the few tutorials I found online. And they've certainly worked well for me.

The wiring diagram is as follows:


This is for the OEM sensor. For a generic sensor, OEM black = white, OEM white = grey, OEM blue = black.

By installing a low pass filter into the O2 sensor circuitry, the aggressive voltage spikes are mitigated by the resistor, which allows only a certain amount of electrical current to pass in a given amount of time. The capacitor helps by charging and discharging the voltage, further smoothing out the curves. Some have installed only the resistor onto the signal wire, which sometimes is enough to smooth things out enough to avoid the ECU throwing a code. However, by using the capacitor as well, electrical current can be provided during the low voltage "dips", further helping reduce the overall variation. By using only the resistor, you'd likely smooth out the spikes but still have some significant dips.

Unfortunately I didn't take photos when I wired this up on my sensor. It's probably better that way. My soldering isn't the neatest. But essentially, you simply cut the signal wire (blue if OEM, black if generic) and ground wire (white if OEM, grey is generic) then wire the resistor on the signal wire and the capacitor between the signal and ground wire. I'm not sure if it matters whether the capacitor is placed between the resistor and sensor or resistor and ECU. I have mine between the resistor and O2 sensor and it seems to work fine.

And voila! Smoothed out voltage band:



Bank 2 is actually a bit smoother than Bank 1 now. And like I said, it's been 650 miles with no P0430 code.

Of course, you'll want to tape things up so nothing gets short circuited, since you might have exposed leads from the capacitor or resistor. You'll also want to make sure not to hack up the wiring too much, since there's not a lot of slack between the connection of the sensor to the cat and the connection to the harness. They designed the sensor wiring to be just long enough to go from the cat to the harness without a lot of extra slack.

If you have the Torque app and a Bluetooth OBD-II module, you can monitor your voltage levels after install to make sure they look good. If you don't, the Torque app is free and Bluetooth OBD-II modules can be had for around $20 or less on Amazon and eBay.

Time will tell if this works in the long run. I don't see why not, unless one of the components goes bad. If the resistor goes bad, it could result in the spikes coming back, or the voltage blocked altogether resulting in 0V, which will trigger a code. I'll update if I run into any problems.