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2003 CTS
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10 Posts
Discussion Starter #1
Hi CTS forum!

I have had these codes popping up intermittently the last few days. I pulled them with the onboard scanner.

P0161--- bank 2 sensor 2 heater low voltage
P0157--- bank 2 sensor 2 low voltage
P0158--- bank 2 sensor 1 high voltage
P0153--- bank 2 sensor 1 slow response
P2099--- bank 2 post cat fuel trim too rich

I don't think it's very likely that 2 O2 sensors would fail at the same time so I suspect that the ECM or another component is to blame.

Do y'all have any ideas on what this issue could be?
 

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2003 CTS 1SC Luxury Sport
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1,017 Posts
When you have a rich code accompanying the 2 related sensors on the same bank, I would say that sensors fouled. Fix your rich code and replace the sensors. Doesn't sound like an ECM.
 

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2003 CTS
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2,339 Posts
the O2 sensors are pretty easy to change. you may need a can of PB blaster, WD40 or something of the sort to break them loose. post cats can be reached with the car on a set of ramps. bank 2 is drivers side. I got mine from amazon or rockauto.com, pretty reasonable if I remember correctly. do a search in this forum for O2 sensors, I am sure there have been some write ups, or check the DIY at the top of the page
 

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2003 CTS
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10 Posts
Discussion Starter #4
Thanks for your replies guys! jran, how would you test to see if the engine is running rich? And what could cause that? Maybe a bad injector?
 

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2003 CTS 1SC Luxury Sport
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1,017 Posts
Only way to test and see if it's running rich is to get a scan tool and watch your long term fuel trim. Negative is rich and positive is lean. Ideally you want 0%, but + or - 5% is realistic and still within perimeters. Lots of things can cause an engine to run rich, O2 sensors being one of them. Bad set of spark plugs, a leaking injector or fuel pressure regulator, the list can go on.
 

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2003 CTS
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10 Posts
Discussion Starter #9
josney, It cost $900 at the stealership. I know I could have done it for a lot cheaper if I bought one online and found a shop with a Tech 2 to program the VIN, but my parents wanted a warranty on the work.

Corvanti, I hope the new ECM fixes your problem. I'll keep an eye on your thread.
 
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