P0156 is an OBDII trouble code that occurs in the Hyundai Tucson. It is typically caused when the O2 Sensor voltage is not within its specified operating range.
- Bank two will be the side of the engine with cylinder 2 in the firing order.
- Sensor 2 is aft of the catalytic converter.
Hyundai Tucson P0156 Symptoms
Often, the only symptom of P0156 is going to be the service engine soon light. In some cases, there can be other symptoms as well. These symptoms include:
- Rough running engine
- Smelly exhaust
- Service engine soon light on
Most of the time, it’s not a breakdown risk. But, like anything that causes the service engine soon light to come on it is a good idea to have it fixed as soon as possible.
Driving your vehicle for really long periods of time with P0156 can potentially lead to engine or catalytic converter damage.
P0156 Causes: Hyundai Tucson
Here are the most common issues that cause the P0156 code in the Tucson. They are presented in order (somewhat) of most to least likely to cause the problem.
- Bad Oxygen Sensor– The oxygen sensor itself is one of the most likely reasons that P0156 is triggering your service engine soon light. Although it is a temptation to replace it right away, it wouldn’t hurt to check out the wiring harness around it beforehand. See directly below. They are relatively affordable at Autozone or Amazon.
- Wiring Harness Damage– The wiring that goes to the front and rear oxygen sensors is very susceptible to damage. This is due to the fact that O2 sensors are under the chassis where they are subject to punishment from road debris, and they are subjected to a lot of exhaust heat. The downstream sensor is especially susceptible to this problem Here’s how to find a short in the wiring harness (Youtube)
- Damage to the Terminal– The terminal that the oxygen sensor connects to (the plug) is also relatively susceptible to damage. You’ll want to make sure that there is voltage going to it. There’s more on that directly below.
- Exhaust Leak– If the exhaust is leaking, then it’ll allow oxygen in that shouldn’t be there. That can throw this code.
- Wrong O2 Sensor– If you are getting P0156 after having recently replaced your Oxygen sensor, it may be that the replacement is wrong or bad.
Tucson P0156 Diagnosis
Here is a fantastic video that covers all aspects of diagnosing a P0156 trouble code It’s for a VW, but the code is universal.
It is possible to diagnose the P0156 with a multimeter. If you use the multimeter, you’ll know whether or not the voltage coming to and from the oxygen sensor is within spec, this can help you determine if it’s your Tucson’s O2 sensor, or wiring harness that’s the issue.
If you don’t have access to a multimeter, it certainly wouldn’t hurt to check the wiring to between the fuse box and the Oxygen sensor first. If it ends up being a wiring issue, it’ll save you money over buying an unnecessary O2 sensor.
You can also use a voltage test light to determine whether or not the oxygen sensor is getting any voltage at all (they’re about $5 at Walmart).
If it’s not getting any voltage, attach the test light to the harness plug and shake the wiring a little bit. If the light comes on, even for a second, you know that you have a short circuit causing the P0156 trouble code.
Conclusion
Most of the time with P0156, it’s going to be the oxygen sensor itself that has caused the code to trigger. Good luck finding whatever caused it in your Hyundai Tucson. If you have anything that you would like to add, please feel free to leave a comment below.