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2003 CTS Base model
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Discussion Starter #1 (Edited by Moderator)
Been having the check engine light and some codes popping up lately. Mostly o2 sensor circuit codes - PO 157, 158, 153. Also had a PO 430 catalyst code the other day but that one hasn't reappeared like the others. Car is just about to turn 90k miles.

Blue Driver OBD monitor is supposed to show common fixes for these codes, but shows nothing in this case. Clearing the codes last from 1-3 days and then they reappear. I had no illusions that the issues were gone, just got sick of looking at the light.

So far, online searches have shown that this may be an ECM issue. I don't want to start throwing parts at this unnecessarily. Anyone had similar experiences? Fixes? Suggestions? Thanks!
I'm considering this option: http://www.ebay.com/itm/282004674078?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
 

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'05 CTS-V
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Re: CEL & codes

If you're looking up codes as "PO 157", etc, that may be why Blue Driver OBD monitor isn't finding anything. It's P0157 (the number zero, not the letter O).
 

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Discussion Starter #3
Re: CEL & codes

If you're looking up codes as "PO 157", etc, that may be why Blue Driver OBD monitor isn't finding anything. It's P0157 (the number zero, not the letter O).
Just a typo sir. Blue Driver lists code numbers along with a brief description of each code set on the iPhone/iPad screen. That's how I knew they were O2 sensor and catalyst related. From what I've found so far, it doesn't seem to make sense to throw O2 sensors at it and not have the problem fixed.
Trying to determine if $150 spent on the ebay item will be worth the time & effort.
 

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Discussion Starter #5
Re: CEL & codes

Ahhh, got it. Well, hopefully others can chime in with their experience with those codes.
Thanks for updating the title of the thread. The car appears to be running normally, so I haven't rushed to ebay just yet to buy that ECM. Looking at past threads, I figure someone has had a similar experience and will post sometime in the near future.
 

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Discussion Starter #6
I've gone ahead and purchased an ECM from ebay. It's supposed to come programmed with my VIN, so we'll see how it goes. Will post back after installation to report progress.
 

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Discussion Starter #7 (Edited)
ECM replaced. Issue persists. Both O2 sensors Bank 2 replaced. Problem persists, along with a new P0050 code.
One possible issue: I used dielectric grease in the lower (downstream) sensor replacement after cleaning that plug up because it was oil covered. It now occurs to me that when I replaced the ECM it specified not to use anything so I didn't for that. Should I pop that sensor's plug apart and clean it up with electric parts cleaner? The codes showing now are for Bank 2, Sensor 1, which is the upper. No dielectric grease was applied to that. This is becoming a huge pain in my ass.
 

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Discussion Starter #8
This thing is driving me forking crazy. Start the car, engine light is on with codes P0050, P0155 confirmed and P0151 & P0051 pending (per BlueDriver OBD scan).
Clear the codes and the car will drive as far as you want to take it without the CEL coming on. Shut the car off and restart it, light reappears with the same codes.
 

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Discussion Starter #10 (Edited)
http://www.troublecodes.net/pcodes/p0050/
You might check the relay and fuses for the o2 heater circuit.
Pre O2 fuse looks good. Post O2 fuse good. I'm not finding any information on relay for these sensors. The battery side plug for Sensor 1, Bank 2 is a bear to get at. I don't think I could get test leads in there even if I knew which contacts to touch them to.
Checking the fuse block on the Pre and Post O2 slots, I had black meter lead to ground and probed each side with red. Getting about 3.5 volts on one side and 12.5 on the other in both fuse locations. Didn't have much luck checking resistance on the sensor side plugs from the removed sensors. My electrical knowledge is a little limited.
 

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04 CTS 91 Aristo
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I'm not sure I understand your language. What is a pre 02 fuse? What is a battery side plug? What are the pre and post 02 slots? Are you talking about upstream and downstream o2 sensors? The sensor side plugs means the o2 sensor connector?
 

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Discussion Starter #12
I'm not sure I understand your language. What is a pre 02 fuse? What is a battery side plug? What are the pre and post 02 slots? Are you talking about upstream and downstream o2 sensors? The sensor side plugs means the o2 sensor connector?
Pre and post O2 fuses are located in the under hood fuse box. From what I understand, they power the O2 sensors. Two 10 amp fuses shown below.
2010-01-23_194112_stop.gif

When I say battery side plug, I mean the powered plug that the O2 sensor lead plugs into. The sensor side means the plug hanging from the O2 sensor itself.
 

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Ok I understand now. Can we dig up the electrical diagram or factory service manual? We have to dig into the exact procedure otherwise I can tell this is just going to get more confusing.
 

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Discussion Starter #14
I threw in the towel on this one. Dropped it off at a local shop this afternoon. They asked me to bring the original ECM in with it, so I did, along with the original O2 sensors. I'll post back when I get a verdict.
 

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Discussion Starter #15
So far, the shop has discovered that one new O2 sensor is bad (ebay special, go figure). They're now leaning toward an intake leak causing a lean condition. I told them to fix a seeping valve cover gasket while it's apart. One this car comes out of the shop, it's DTFR. Second used Cadillac, second time large headache. But I want it right before I put it on the market.
 

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I understand completely why you want to get rid of it Hammerhead. On the o2 sensors, I usually only use Bosch. It's one of those items like spark plugs where you can't really get away with cheaping out on. Actually the o2 sensor isn't that expensive, it's just that there's 4 of them. You should have your shop change the spark plugs while they're at it because you have to remove the intake manifold to do it and the spark plugs are cheap. The thermostat wouldn't be a bad idea either, especially on an 03 because the thermostats fail so often on those.
 

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Discussion Starter #17
I understand completely why you want to get rid of it Hammerhead. On the o2 sensors, I usually only use Bosch. It's one of those items like spark plugs where you can't really get away with cheaping out on. Actually the o2 sensor isn't that expensive, it's just that there's 4 of them. You should have your shop change the spark plugs while they're at it because you have to remove the intake manifold to do it and the spark plugs are cheap. The thermostat wouldn't be a bad idea either, especially on an 03 because the thermostats fail so often on those.
Thanks for the heads up on the plugs. I'll stop by this morning and let them know to do that while it's apart. And yes, lesson learned on trying to cheap out with the sensors. It worked with the ECM, but apparently not the sensors.
 

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Discussion Starter #18
Just stopped over to the shop to have them also do plugs & thermostat while it's apart. He took me in and showed me something that they found once the intake and coils were removed. The cavity (galley?) beneath the rearmost coil on the driver side had oil laying in it and the bottom side of that coil was covered in oil, probably causing a misfire. The valve cover on that side has been seeping since I bought the car, but regular oil checks never showed it to be losing any oil. Valve cover gaskets have been on the list of things to do since I took it over there anyway.
 

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You'll need the spark plug tube seals. They just press into the valve cover. Don't worry too much about the coilpack because if it is failing, you can replace that one without removing the intake manifold. The coilpack might've overheated if it was shorting out though. If they have an ultrasonic cleaner, it wouldn't be a bad idea to get the fuel injectors cleaned up too. I'm assuming he removed the lower intake manifold as well because I couldn't get the driver's side valve cover off without first removing that. If he removed that, the injectors came with it.
 

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Discussion Starter #20
You'll need the spark plug tube seals. They just press into the valve cover. Don't worry too much about the coilpack because if it is failing, you can replace that one without removing the intake manifold. The coilpack might've overheated if it was shorting out though. If they have an ultrasonic cleaner, it wouldn't be a bad idea to get the fuel injectors cleaned up too. I'm assuming he removed the lower intake manifold as well because I couldn't get the driver's side valve cover off without first removing that. If he removed that, the injectors came with it.
Haven't spoken to them since about 7:30 this morning. And I was tied up most of the day so I'm not sure where we're at on the thing.
 
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