P2196 is a generic diagnostic trouble code that indicates that your Cadillac ATS’s first oxygen sensor on bank one is stuck rich. It does not necessarily mean that the vehicle itself is running too rich. This code is the opposite of code P2195, which indicates the oxygen sensor is stuck lean.
P2196 Definition: Oxygen Sensor – Stuck Rich (Bank 1, Sensor 1)
Oxygen Sensor
When you get P2196 it means that the voltage level being recorded by the oxygen sensor is stuck on the rich side (think like a high waveform). Your engine’s computer uses the data from the oxygen sensor to adjust the air-fuel mixture for optimal combustion. There’s information on how to test and determine if your ATS’s oxygen sensor is bad in the diagnostic section below.
Stuck Rich
A rich condition means that there’s too much fuel in relation to air entering into the combustion chamber. When your oxygen sensor is “stuck rich” the data value that it is sending to the PCM is consistently measuring too high.
Bank 1
Bank one is the part of your ATS’s engine with the first cylinder. You only need to concern yourself with this if there is more than one cylinder head (meaning inline-four and six engines get a pass). If there is more than one cylinder head, you’ll need to determine which bank is which.
The first cylinder is usually the furthest from the transmission (as a rule, it’s not definite for all vehicles). But, you can use this guide to help you determine where bank one.
Sensor 1
Once you find bank one, finding sensor one is pretty easy.
Sensor one would be the first sensor when tracing your ATS’s exhaust from the combustion chamber to the exhaust pipe. It’s usually at the end of the exhaust manifold, or right where the exhaust manifold bolts up to the exhaust itself.
Cadillac ATS P2196 Symptoms
Usually, there are symptoms associated with P2196. Here are the most common ones:
- Black/Sooty smoke from the exhaust
- Poor MPG
- Engine runs rough or down on power
Cadillac ATS: P2196 Causes and Diagnosis
Below we have listed the most common causes of P2196, they are listed in an order of ease of diagnosis weighted with the likelihood of being the problem.
There are a lot of potential causes for P2196. Check for any other codes. If there are, they can provide valuable insight.
1. Check the Wiring Harness at the O2 Sensor
Your Cadillac ATS’s B1S1 O2 sensor has a tough life. It is right there on the hot exhaust, it also has to deal with a lot of engine vibration. The wiring harness to this sensor will fail more than almost any other automotive wiring.
Check to see if the wiring is burnt or frayed. Make sure that the pigtail that plugs into the sensor is snugged in tight and has no damage itself. You can do this pretty quickly with a flashlight. You can usually see this oxygen sensor without having to take anything apart.
You can use a multimeter to determine if there’s a short or open circuit. This article can make you an expert on the subject in no time.
2. Swap Test (Optional V6, V8 Only)
If you happen to be lucky enough to have a ATS with a V-8 or V6 engine, you can do something called the swap test. Basically, it involves removing the bank one sensor one oxygen(B1S1) sensor and replacing it with the bank two sensor one sensor(B2S1).
If you’re comfortable with a scan tool, you can skip this part and move straight on to capturing the short-term and long-term fuel trim values below. If you’re not comfortable with a scanner though, this test can save you a lot of time.
Here’s how to do the swap test:
- Clear the DTC codes with your scanner.
- Swap the Bank 2 Sensor 1 O2 sensor with the Bank 1 Sensor 1. It’ll be on or right after the exhaust manifold.
- Run the engine until the check engine light comes back on.
- If the code changes to P2198 (which indicates the O2 sensor on Bank 2 is stuck lean), that is enough proof that you need a new O2 sensor. Since the problem changed sides of the engine, we can be confident that the sensor is at fault.
- If the code remains P2196, you’ll need to continue pursuing your diagnosis, knowing that both O2 sensors are working fine.
3. Capture the Short/Long Term Fuel Trim Values
If you happen to have access to a scan tool, you can use it to capture the short and long-term fuel trim values. You’ll need to make sure that your ATS’s engine is warmed up before you do this.
Doing this test will help you determine if the O2 sensor is operating within spec without having to do any looking under the hood. You’ll need to compare the values that you capture with your tool with the values the manufacturer specifies.
While this isn’t a skill most DIY mechanics have, the concept is simple, and you can learn enough to use fuel trim to your advantage by watching this 11-minute video (it’s worth it).
Related: Cadillac ATS Bad Oxygen Sensor
4. Vacuum Leaks
Often a worn or brittle vacuum line will allow unmetered air into your ATS’s engine. When this happens, it creates a lean condition.
You can test for a vacuum leak around the vacuum lines and the intake manifold. A common method is to spray carb cleaner around the intake/vacuum lines. When the spot is found the engine will rev higher with no throttle input.
Obviously, carb cleaner is super flammable. So be CAREFUL. Make sure you have a form of fire suppression available to you.
5. Other P2196 Causes
The steps listed above cover the most common causes of P2196. The trouble with this code though is, there are a lot of other things that can cause it as well.
Here are other things that can cause P2196:
- Bad or dirty MAF sensor
- Fuel pressure is too high (bad fuel pressure regulator usually, adds too much fuel to the air/fuel ratio)
- PCV system leak (cracked hoses going from the head to the intake)
- Bad fuel pressure sensor
- ECT Sensor
Bottom Line
In the Cadillac ATS, P2196 is usually caused by a bad oxygen sensor.
Doing your due diligence can save you a lot of time and wasted money/effort. Good luck!