What this code means
P115E may indicate that NOx Sensor 1 is not operating within the range the control module expects.
What the vehicle may do
- The vehicle may display a Service Emission System or Service Exhaust Fluid System warning.
- The reductant system can be affected when this fault sets.
- The vehicle may continue to run while emissions-system operation is limited.
Possible fault areas
- NOx Sensor 1 or its related circuit operation may be involved.
- NOx sensor supply or heater operation can be part of the fault area.
- Induction, exhaust, or turbocharger leaks may affect the diagnostic path.
- The reductant control system may be involved because it controls reductant heating and dosing.
Diagnostic path
Code overview
On a 2020 to 2025 Chevrolet Silverado 2500 with the 6.6 diesel, P115E may indicate that NOx Sensor 1 is operating outside the range the control module expects. The truck may display a Service Emission System or Service Exhaust Fluid System warning, and reductant-system operation can be affected when this fault sets. Broadly, this can involve NOx Sensor 1 or its circuit operation, the sensor supply and heater side, the reductant control system, or an induction, exhaust, or turbocharger leak that can skew what the sensor is seeing. The reductant control module controls reductant heating and dosing, so keep that system context in mind while you work the code. For this monitor to run, Ignition Voltage has to be greater than 11 V, NOx Sensor 1 Supply Voltage has to be greater than 10.8 V, the NOx Sensor 1 heater has to be allowed, and the related communication fault must not be set. Once those gates are met, the monitor runs continuously. P115E sets when NOx Sensor 1 is not within a calibrated range for greater than 2 s.
Start with the setup checks
Start with the basic system checks and follow a structured diagnostic approach before going into the code chart. Keep the diagnostic category context in mind too, because this path uses the category result to guide the decision instead of treating the whole code family like a direct parts list. Then turn the ignition on with the vehicle in service mode. Do not skip that setup, because the rest of the test depends on the modules being awake and the data being valid.
Check the leak-path first when it applies
Next, do not judge P115E alone until you know whether the specific companion fault path for this test is present. If that companion fault is not set, move on to reproducing the operating conditions. If it is set, first check that the induction system is not leaking and that the exhaust system or turbocharger is not leaking. If you find one of those leak conditions, repair it or replace as necessary. If that companion fault is present but those leak conditions are not found, this diagnostic path calls for replacing B195A Nitrogen Oxides Sensor 1.
Reproduce the fault and make the decision
If the leak-path companion fault is not set, operate the vehicle so the monitor can run. Reproduce the operating conditions, or drive it under the same captured conditions from when the fault was recorded. After that, check whether any fault in this same NOx sensor emissions group has set. Do not read through the whole family as a parts list; just use the group result to guide the decision. If any fault in that group sets, this path calls for replacing B195A Nitrogen Oxides Sensor 1. If none of those faults set, the result is all OK at this time.
Verify and close out
After completing the repair, verify the repair and confirm the code stays gone. If the vehicle is displaying the Service Emission System or Service Exhaust Fluid System warning, use the scan tool control function for the Reductant System Tamper Warning Service Bay Test only when that warning message is displayed. That test is the step used to clear the driver information message for the applicable system. The takeaway is simple: for P115E, prove the monitor conditions, rule out the leak-driven path when it applies, then follow the NOx Sensor 1 decision exactly instead of guessing. For more diagnostic training, visit stepdiagnostics.com.
Final check
P115E can be approached by confirming the monitor may run, checking the specific leak-related path when applicable, and then following the NOx Sensor 1 decision path.
For more guided automotive diagnostics, visit STEP Diagnostics.
