P0037-Audi-
P0037 is a generic trouble code, which means that it has the same definition for the Audi A3 as it would any other vehicle.
It indicates that the O2 sensor at bank 1 sensor 2 has a heated element that is sending a signal back to the ECM that is below its normal operating range.
The most common fix for P0037 is a new heated Oxygen sensor or a repair to the wiring harness.
P0037 Definition: Heated O2 Sensor -Circuit Low (Bank 1, Sensor 2)
Here’s the definition of P0037 for the Audi A3 broken down by its two main parts:
Heated O2 Sensor
The heated oxygen sensor is responsible for measuring the oxygen content of the exhaust. The PCM uses this data to adjust the air-fuel mixture to the optimal 14.7 parts air to 1 part fuel.
Your A3’s PCM can turn on the heated element to raise the temperature of the Oxygen sensor to enter closed loop operation quicker than it otherwise could.
Circuit Low
“Circuit Low” Indicates that PCM is having an issue detecting a response from the heated oxygen sensor circuit or that the signal coming from it is below the threshold for regular operation. The service engine soon light will come on, and P0037 is stored in the PCM’s memory.
Bank One, Sensor Two (B1S2)
Bank one is the part of your Audi A3’s engine with the first cylinder. You only need to concern yourself with this if you have a V6 or V8 engine (more than one cylinder head).
Bank one is the side of the engine with the first cylinder. Bank one should be the cylinder head that is facing a little more forward than the other.
Sensor 2
Sensor one is easier to identify. Start from bank one and follow the exhaust. It’s the second one in line. The HO2 sensor should be right after the catalytic converter.
P0037 Symptoms: Audi A3
There aren’t any noticeable symptoms associated with P0037, as long as it appears by itself.
Once the oxygen sensor heats up enough from the exhaust, the need for a heater disappears, and everything should be normal (other than the check engine light not turning off).
- Check engine lght
Audi A3: P0037 Causes & Diagnosis
Here are the most common causes of P0037 and a decent order of operations for diagnosing it.
1. Check the Wiring on Bank 1 Sensor 2
Since the PCM is not getting a response from the H02 sensor, check the wiring harness for damage.
First, inspect the harness going to your A3’s B1S2 H02 sensor. Pay extra close attention to where the harness may have come into contact or rubbed something. Look for burnt or damaged wiring. Bad wiring is a VERY COMMON cause for P0037.
Take at where it plugs in and see if there has been any damage to the pins. If they appear corroded, get some electrical contact cleaner and clean them up. If they are damaged, you will need to repin or replace your wiring harness.
2a. Test the Oxygen Sensor – Swap Test
This can not be done if you have P0037 and P0057
If your Audi A3 happens to be a V6 or V8 model, you can do the “swap test.” This involves clearing the codes and seeing if the code “jumps” to bank 2 sensor 2.
Here’s how the swap test is done:
- Clear the DTC codes with your scanner.
- Swap the Bank 2 Sensor 2 O2 sensor with the Bank 1 Sensor 2. It shold be right after the catalytic converter.
- Run your A3’s engine until the check engine light comes back on.
- If the code changes to P0057, that’s proof enough you need to replace the oxygen sensor syou swapped.
- If the code remains P0037, you’ll need to continue pursuing your diagnosis, knowing that both O2 sensors are working fine.
2b. Test the Oxygen Sensor – Capture the Short/Long Term Fuel Trim Values
If you happen to have access to a scan tool, you can use it to capture your A3’s short and long-term fuel trim values. You’ll need to make sure that the engine is warmed up before you do this.
Doing this will help you determine if the HO2 sensor is operating within spec without looking under the hood. Compare the values that you captured 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).
3. Not Likely – Bad ECM
It’s not very likely that a bad ECM caused P0037, but it can happen. We recommend taking it to a shop before attempting to replace it.
Conclusion
P0037 in your Audi A3 is most likely caused by a bad Oxygen sensor, or the wiring going to/from it.