P0420, P0430, P0421 Catalyst Efficiency Codes

So many techs fear these group of codes because they have been bitten before by them. In my opinion, these are some of the easier codes to solve if you attack it systematically. The first step is to know the enemy. The general code set criteria is as follows; When the the downstream oxygen sensor is within 80% of the activity of the upstream oxygens sensor during a catalyst test the code is set. The key to this is graphing our scan data. Years ago scan data was much too slow to trust graphing it. But, todays datastreams and professional scantools make this a trustworthy venture. Here is a snapshot of`data that was graphed.

In the above we have the following pids graphed. Engine speed, upstream oxygen sensor, downstream oxygen sensor, and throttle position voltage. As you can see we are raced up at 2514 rpm. Is this catalytic converter doing a good job right now? No, not really at all. What I stress here is look at the symmetry between upstream and downstream sensors. They are almost identical. Are we within 80% activity? Looks like it. Now, before you plunk that money down for a catalytic converter there is a couple of things to do. I always take the car for a thorough test drive and recheck oxygen sensor activity out on the road. There are many converters that need a hard test drive to verify operation or "light off". The other test procedure I do is either introduce carb spray or propane into the system to make sure both upstream and downstream oxygen sensors go full rich. Sometimes, I can get away with just "flashing" the throttle a couple of times and checking. Confirm that the vehicle is at operating temperature-bad thermostats,  radiator flow, or improper fan operation can play havoc with catalyst operation. The final item to check is fuel trim. Make sure your fuel trims are tight. Fuel trims that are elevated either way will cause catalyst issues.

As you can see in the above snapshot our fuel trims are excellent. Always check fuel trims at an idle, raced up 2500 rpm no load, and at cruise steady throttle out on the road. There is usually a reason behind catalytic converter failure. The reasons can range from a converter that has been digesting misfires, bad fuel trims, and oil contamination. I see the oil contamination issue quite a bit on those pre cat (where the cat is part of the exhaust manifold or directly after the exhaust manifold) vehicles. If you have any of these issues the new converter will go belly up in short order.  So now you are ready to order the catalytic converter. Not yet, definitely run a tsb (technical service bulletin) search to see if there are updated parts or reflashing pertaining to your issue. Now you are ready to get prices on the catalytic converter. A call to the OE dealer gives you a price of $842.31-geez the car is only worth $2000.00. A call to the parts house or a converter supplier and the price is $231.28. Why the big difference? First off make sure the aftermarket one is a direct fit. Nothing like giving the cheaper price only to find out you need the $95.00 adaptor kit and have to be  Michaelangelo with the welder to get this to fit. The second is make sure that the converter you are getting is OBD2 C.A.R.B (California Air Research Board) certified and they can supply the paperwork supporting this. I have seen too many times the shop sells the cheap converter only to have me come back multiple times and the converter to be exchanged two times before it is realized this cheap converter is in fact cheap. I have also seen where the manufacturer will hide behind that the fuel trim is off, the vehicle is not reaching operating temperature, the oxygen sensors are incorrect when there is a problem. This is why I always document everything. There are certain vehicles I do not recommend aftermarket catalytic converters on period. They are 2001 and up GM cars, Honda vehicles, and Subaru vehicles. It seems the aftermarket cannot make the proper converter for these applications, you get what you pay for. 
Another item to be wary of is exhaust leaks ahead of the catalytic converter on codes that never seem to be fixed. An exhaust leak ahead of the converter no matter small will introduce outside oxygen into the exhaust stream. Causing problems and ruin your day. A smoke machine can be used to find small leaks. So what if you have a A/F ratio sensor upstream instead of a conventional sensor. Just look at the downstream sensor graphed and use the hints I have given to diagnose these cars. Most techs think that the catalyst monitor is run during steady highway speeds. That is true of most cars. But, late model GM vehicles will run it at an idle after a highway run. Know your enemy, check your drive cycle routines to determine when it looks at converter status. I hope this helps the next time you have one of these in your bay.

Ottotest Update

I had a chance to use the Ottotest on a 2002 GMC Sierra Denali Pickup. This truck was loaded with every option. First thing I did was do a DTC health check with the Ottotest. This is where the scanner polls all the modules for communication and codes. The Ottotest did this procedure with ease and then gave me a summary of how many modules it saw and how many had codes. One interesting note here is that if there was a module that didn't communicate you would have to go back into the module log to see which module didn't communicate. The truck was in the shop for no DRL (Daytime Running Lamp) operation. The Ottotest did a great job of showing me everything I needed to diagnose this issue. The bi-directional functions were excellent. The other item of mention here is I was able to graph BCM and ABS data on this truck. This was a big complaint of mine. So, I tried graphing BCM and ABS data on my 2001 Dodge Durango-still nothing. What is with that? I can graph GM data but not Chrysler? I also tried another Hyundai vehicle recently to see if I could get Air Bag codes and data-no dice. I checked for recent scantool updates, there were none. I reported all this back to Blue Streak via the feedback function on the scanner. Let's hope they are listening. 

A Quick Word of Thanks

There were many people I would have liked to thank over the years and I promised myself I would if I ever got the chance. Well, my new motto is why wait? Of course, I have to thank my family. My Dad of course who started me on my automotive journey. What started out as just wanting to spend some time with him expanded into a career for myself. The "shop" was the hub for my formative years growing up. It was where I spent summers as a kid, afterschool as a teenager, and "overnights" as a twenty something. I learned about life in an automotive repair shop. I want to thank my Mom for teaching me never to take the easy way out. That has proven usefull in business and in life. My brother for showing me the lighter things in life. My wife for putting up with my ocd and intense behavior. Also, when she is updating me on the days events and I am thinking about that amp ramp pattern on that ignition coil instead of listening to her. Is it good, bad, hmmmm. She puts up with a lot.
Then there are my techline bretheren that I spent years with. Cesar, Jose, Mike, Peter, and my good friend Joey "Bag of Donuts" who is without a doubt the most intelligent all around person I know. These guys I still keep in touch with and trade automotive war stories. I have to thank Chris and Ray from Motormouthradio who shout out my website and talk me up from time to time on their radio show. These guys have more fun doing a radio show than I thought possible.
I have to thank all the great instructors and trainers I have had throughout the years. I have had some really good ones. The best though is John Thornton. His knowledge and teaching style is far superior to anyone else. If you ever have a chance to catch John in action do so. You won't be disappointed.   

1996 Ford Contour

I am called to Mr. H's shop for a full day of diagnostics. In fact he has so many for me this day I get my own parking lot. I feel special. One of the cars is a 1996 Ford Contour 2.0L with 63,146 miles on the odometer. Car came in with a P0135 code (Bank 1 Sensor 1 Heater Malfunction). Mr. H tried a new upstream oxygen sensor and the code came back immediately. Time to do a little testing. Since this car only has one bank the chances of the wrong oxygen sensor being changed is cutdown. You don't know how many times I have seen this, especially Nissan vehicles. Sure enough the correct oxygen sensor was changed. First things first. Lets make sure we have battery voltage going to our problem child key on engine off. So I backprobe the heater power wire right at the upstream o2 sensor.

Not exactly battery voltage. Now we know why we were setting the heater code. No battery voltage means no heater operation. Time to break out the wiring diagram.

Now we have some directions. Looks like this circuit has a fuse labeled HO2S that feeds both the upstream and downstream heater circuits for the oxygen sensors. Ok, lets check the fuse. this fuse is located in the underhood fusebox. Checking the fuse with a DVOM tells me the fuse is getting battery voltage and the fuse is good. Now what? Lets divide and conquer. We have a connector and a splice joint between the fusebox and the o2 sensors. I always choose connectors over splice joints whenever possible. Reason being connectors are usually easier to find than splice joints. But first look at the fusebox picture.

There is a hole drilled in the side of the fusebox with a snipped butt connector end attached to a wire. When I see this I always get worried. It usually means someone has been trying to "reengineer" the factory wiring instead of repairing it correctly. My catch phrase for this usually goes something like this-"A 100 years of automotive engineering gone in a second." Now, the integrity of the factory wiring is suspect. I follow this rogue wire around the left front strut tower along the firewall to its destination. Of course this wire was not attached to anything. It was defying the laws of gravity in spots.

And there is our destination of the orphan wire. "Expertly" scotch locked to a wire going to the PCM (Powertrain Control Module). Oh boy. Is this our problem? Is this another problem? Was this the remanants of some long ago disabled anti theft device? Well lets get back to testing. As I was saying I always like connectors over splice joints. So I go after C100-located right behind the left front strut tower.

I locate the heater power feed wire at C100.

As you can see I have the same voltage at the o2 sensor at the power side of C100. The power side being the one that is on the power feed side from the fusebox. So now I know my voltage drop is from the underhood fusebox to C100.  Remember, divide and conquer. Do I have a rotted wire under the fusebox? It is located right next to the battery. I can't get the rogue wire out of my head. I know it is linked. Hmmm. I start wiggling the HO2S fuse and.....

My meter still stuck in C100 starts to read battery voltage and every voltage in between. Bingo! I pull the fuse out and my first clue is that it pulls out rather easy. I tweak the fuse a bit and reinstall. Same result. I then inspect the fuse cavity.

It doesn't look like much. I removed the fuse next to it for comparison. The terminal is spread open causing contact issues. There is our voltage drop. Now I know where that rogue wire was going at one time. That extra added bulk at the terminal opened it up. Now that there is just a fuse in there (as intended) there is a poor connection. A couple of tries and I was able to close up the terminal sufficiently. A quick run of oxygen sensor amperage on the scanner and a test drive reviewing mode 6 data confirmed the repair.

Ottotest Update

 Well, I started to incorporate my new Ottotest into my testing. I had a chance to use it on a 2004 Hyundai Sonata with an airbag lamp on. The Ottotest claims that it does SRS ( Supplemental Restraint System) code retrieval and data. Well, it doesn't. This is not uncommon. Snap On makes the same claims as well. This is very unfortunate because I see a lot of Hyundai/Kia problems and this was one of the main reasons I purchased this tool. Although, there was a new update just released this week that I did download after seeing this car. Did it address this issue? We will find out that is for sure. Stay tuned.........

The Arsenal

There it is. What I use out in the field. From my newest tool the new Ottotest to my oldest my old reliable Fluke 88 complete with "ghosting" characters. Each tool has its own specific uses. In addition to all this hi tech tooling, I cart around a fair share of jumper wires, homemade harnesses, test leads, fuel pressure gauges, and common hand tools. In addition, I have access to some factory scantools when I need to. You never know what you are going to need so I pack everything all the time. I use Alldata for an information system along with OE websites. My laptop is loaded with a VE (Volumetric Efficiency) calculator program that I use all the time. In addition I use AES Wave and Annowave to save and annotate downloads from my tools. This proves extremely useful to show "before and afters" to my customers. I am always looking to add tooling. Right now, I am looking to add a 4 channel pc based labscope to the stable. I also use powerpoint presentations when I visit new shops to illustrate what I can do for them. There are always new tools coming out all the time, I would love to have them all. So if anybody wants to donate a Ford IDS or a Nissan Consult to JWR Automotive Diagnostics feel free to do so.