05 STS P0430 (bank 2 cat efficiency)

[kevm14]

My check engine light came on when I was running an errand this morning.

I had three guesses:
- Cat inefficiency
- Low engine temp (I think my thermostat is running the engine a little cold so I thought maybe it was taking too long to warm up to 195)
- Battery voltage (still sort of not sure about this charging system - it charged at a max of like 13.6 on a 15 degree cold start and eventually settled to 13.0 - that just seems so low to me)

Turns out it was cat inefficiency.

Now why did I suspect that? Two reasons:
1) There was a recall on 04-05 SRXs and 05 STSs both with the Northstar for premature cat failure (this code and a rattle), dated October 2010. GM doc ID 2551149.
2) I have seen a pending code for this when scanning with the Tech 2 on previous occasions but it never failed the tests enough to set a light.

More info:
The GM warranty extends for 12 years and 200k which is pretty generous. Not only is my car outside of that by a year, but according to the GM website, there are no open recalls on my STS. So it's either not a recall (which it may not be) or...only some cars were effected (in which case they would have traced to a supplier/batch).

Also, it has been quite cold recently so I'm betting that any kind of marginal cat performance would indeed fall on the side of failed in this weather. I have reset the code and I will see what happens. Not really excited about having to do this as I'll be fighting with cat to manifold bolts/studs/nuts for sure.

Other fun facts:
When I actually scanned the car, there were 7 codes present. Only the cat code P0430 was requesting the MIL. Here are the six silent codes it had:
- EBCM C0250, symptom 71 (unknown DTC, history code, possibly triggered by Tech 2 as I had a Service Stability Control message as soon as I started scanning)
- EBCM C0249, symptom 71 (unknown DTC, history code, same as above)
- Instrument Panel Module U2100, symptom 72 (CAN bus communication alive counter incorrect/not updated, history, possibly same as above?)
- Instrument Panel Module U2100, symptom 00 (CAN bus communication, history, same as above?)
- Driver Position Module B1850, symptom 58 (Seat lumbar horizontal position sensor circuit incorrect reaction after event, failed, also my lumbar does not work and I've seen this code the entire time I've had the car so it is old news but including here for completeness)
- Driver Position Module B1850, symptom 08 (Seat lumbar horizontal position sensor circuit signal invalid, failed, see above)

So of these 7, the only one that is truly real in my opinion is the P0430. I did reset everything except the lumbar as I know that will come back the second I touch the switch again.

Hopefully my Marvel Mystery Oil treatment did not hurt the cat. It's been a few tanks since I did that so I think it's more the cold weather. I was thinking of doing another treatment actually.

Anyway, from here the plan is simple: drive until code comes back.

I was kind of surprised that when sorted by priority, the cat efficiency code was #5 out of 7. But I guess the first four are brakes and comms so maybe it makes sense.

WP_20180102_11_54_25_Pro.jpg

WP_20180102_11_54_30_Pro.jpg

WP_20180102_11_54_35_Pro.jpg

WP_20180102_11_54_42_Pro.jpg

WP_20180102_11_54_53_Pro.jpg

WP_20180102_11_54_59_Pro.jpg

WP_20180102_11_55_09_Pro.jpg

[kevm14]

Here is what the letter looked like. Reading the letter again there are some key things in here. For one, it says "some" 05 STSs. I don't know that they would say "all" if it was really "all" but this implies it's just certain cars. Next, this says there is usually a rattle and decreased engine power. I don't have either of those.

[kevm14]

1) There was a recall on 04-05 SRXs and 05 STSs both with the Northstar for premature cat failure (this code and a rattle), dated October 2010. GM doc ID 2551149.

I don't know what that doc ID is. I did more research.

Date Reported
MAY 01, 2008
NHTSA Reference
#10025282
TSB Reference
#07027
Description: CADILLAC SERVICE CAMPAIGN: SEE DOCUMENT SEARCH BUTTON FOR OWNER LETTER. CATALYTIC CONVERTER - INSPECT/REPLACE. CSC WAS RECEIVED. *NJ

Date Reported
DECEMBER 01, 2010
NHTSA Reference
#10037213
TSB Reference
#SB-10127
Description: GM: SOME 2004-2005 CADILLAC CUSTOMERS MAY COMPLAIN OF A CHECK ENGINE LIGHT, RATTLE UNDER BODY, AND A LACK OF ENGINE POWER. THIS MAY BE CAUSED BY A FAILED CATALYTIC CONVERTER. *RM UPDATED 6/7/11. *PE

[kevm14]

Drove to work. Went out to lunch. Drove home. No light yet. Yay?

[kevm14]

Interesting exchange here from my thread on the Cadillac forum.

Mine has come and gone for a few years. I think I'm starting to hear the rattle but performance, fuel efficiency, etc does not seem to be impacted yet. I too am not looking forward to replacing it...Might look into having my buddy just chop them off and weld up some pipe and do his thing to trick the O2 sensors...Whomever designed this all in one manifold/cat BS needs to strung up and stoned...

My reply:

How many miles on yours? I noticed you have an 06 so whatever batch/supply problem GM had with the 05s, they did not think they had with the 06s. Meaning yours is just....age and miles. Mine may be the same.

His reply:

168k on mine now. CEL first came on around 95k I believe...I called a dealership shortly after it came on to discuss a possible replacement pro-rated under the emissions warranty as I was barely outside of it at the time but even with a small discount it would've been a large repair bill, the OEM part alone was almost $1,000 IIRC. I've just dealt with clearing the CEL and it coming back eventually. Sometimes it comes back same day other times it will go weeks before it comes back.

I haven't even checked prices yet. He's gone from 95k to 168k with the issue and gets between....well, zero days and "weeks" before it comes back. That was my plan anyway.

[kevm14]

Look at this. It looks like the cat is integrated into the exhaust manifold. Because emissions. Sigh. Also Rockauto does not carry GM/AC Delco replacements for this.

Also I appear to have California emissions. Adam and I discussed at lunch about possibly flashing my ECM to a 49 state calibration to possibly give the catalyst efficiency diagnostic less stringency. I should read up on the code to see what the conditions are for setting it, and if by some stretch, they explain the difference between CA and Federal emissions with regard to this diagnostic.

05 STS NC1 cat options.PNG

Anyway these prices aren't unaffordable. I'm actually relieved that I don't need to disconnect the cat from the manifold. It's just manifold to head bolts and a cat to catback flange. Again, assuming the thing slides right down and out, that's not the worst job ever unless the manifold bolts are somehow completely inaccessible.

Funny thing I just realized. I do need engine mounts. And I know for a fact that the driver's side is easier if you remove the manifold. I could combine these jobs somewhere down the road.

[kevm14]

No mention of Federal vs CA emissions.

Description:

A three-way catalytic converter (TWC) controls emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO that are present in the exhaust gas. This process converts these chemicals into water vapor and carbon dioxide (CO2), and will reduce the NOx, converting the NOx into nitrogen.

The catalytic converter stores oxygen. The efficiency of the TWC is determined by the measurement of the oxygen storage capacity (OSC). The engine control module (ECM) measures the catalyst OSC by monitoring the heated oxygen sensor (HO2S) bank 1 sensor 2 and HO2S bank 2 sensor 2, during a steady state cruise. The ECM commands the air-to-fuel ratio lean and then rich for a calibrated number of cycles while monitoring the response time of the HO2S 2. The ECM then establishes an average response time from subsequent air-to-fuel ratio cycles. The difference of the average response time determines the OSC of the catalyst. If the ECM detects that this time difference is less than a calibrated value, DTC P0420 or DTC P0430 sets.

Here is how the test runs:

Conditions for Running the DTC
• DTCs P0010, P0011, P0013, P0014, P0016, P0017, P0018, P0019, P0020, P0023, P0024, P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0068, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0153, P0155, P0157, P0158, P0159, P0160, P0161, P0171, P0172, P0174, P0175, P0221, P0222, P0223, P0300-P0308, P0315, P0335, P0336, P0340, P0341, P0345, P0346, P0365, P0366, P0390, P0391, P0500, P0608, P1137, P1138, P1157, P1258, P1358, P1380, P1381, P2088, P2090-P2095, P2101, P2119, P2135, P2231, or P2234 are not set.

• The mass air flow (MAF) is between 11-80.3 grams per second.

• The engine speed is between 1,088-3,008 RPM.

• The engine has been running more than 10 minutes.

• The predicted catalyst temperature is between 644-902°C (1,191-1,656°F).

• The barometric pressure (BARO) is more than 74 kPa.

• The engine coolant temperature (ECT) is more than 62°C (143°F).

• The intake air temperature (IAT) is between -6°C and +200°C (+21°F and +392°F).

• The engine is in Closed Loop fuel control.

• The vehicle speed sensor (VSS) is more than 35 km/h (22 mph).

• The engine is at a steady cruise, a light load, with no load variation.

• DTC P0420 and P0430 run once within the above conditions are met for 24.8 seconds.

What's weird is I think mine set at idle. I don't quite understand that.

Now I will look up the replacement procedure.

By the way - all OBD-II cars do some form of this test, including my 96 Roadmaster.

[kevm14]

I spoke too soon, kind of.

Driver's side is horrible. It requires removal of the steering rack. And you have to jack up the front diff. Remove a brake line. Move the master cylinder out of the way. Yeah it looks awful.

Passenger side looks a lot better, which coincides with the engine mount job, too. Hey it's a fancy V8 AWD car. I don't know that any of them are a pleasure to work on.

Conclusion: my cats are going to have to be on fire for me to care about this. Ok, slightly more realistically, the code will have to come back in less than a day (perhaps too fast to ready my OBD systems to pass an emissions plug in test) for me to care about this. Well, there's one other one - if something falls apart and physically plugs the exhaust, I will kind of have to deal with it. I don't think that is going to happen any time soon.

[bill25]

I think where they failed was having the cats integrated in the manifold.

[kevm14]

It's more common than you think. Especially on newer cars. Emissions. It lets them put the cat that much closer to the manifold for heat. Plus one less joint to assemble (or leak). It's not a bad idea theoretically. And if my cat were bolted to my manifold, I'd just be struggling with rusted nuts or bolts instead.

I'm hoping the light doesn't come back for weeks. Then it will be fixed forever!