U059F code meaning
Invalid Data Received From NOx Sensor B
Network system Generic code U05xx codes Check engine light
What U059F means
Sensor B is normally the tailpipe NOx sensor behind the SCR catalyst, so its readings decide whether the catalyst efficiency test passes. The code means its CAN frames are present but unusable. GM's 2025 diesel tables run the same counter, protection value and checksum test as for sensor A, here on the post-catalyst signal set, and treat it as Type B. FCA lists it for Ram 3500 to 5500 Cab Chassis trucks with the 6.7 L Cummins: bulletin 18-012-13 (2012) and 18-042-20 (2014, calibration without ammonia delete) reflash the ECM because the light could come on with no hardware fault. U029E means the sensor is missing entirely, U05A2 that sensor B rejects engine data. A stored code blocks the SCR efficiency verdict, so check software before buying a sensor.
U059F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of U059F
- Check engine light on
- SCR efficiency monitor not completing
- No noticeable change in power
Common causes of U059F
- Most likelyEngine controller calibration known to flag false faults (FCA reflash)
- PossibleControl unit of the downstream NOx sensor damaged
- PossibleChafed wiring or water in the connector near the exhaust
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensor b
What each part of U059F means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9F | The exact fault in that area. |
What to do next
- Note U059F and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U059F
What does U059F mean?
U059F means "Invalid Data Received From NOx Sensor B". Sensor B is normally the tailpipe NOx sensor behind the SCR catalyst, so its readings decide whether the catalyst efficiency test passes. It is a generic code, so it means the same on every make.
Is it safe to drive with U059F?
Drive gently and only to a workshop. With U059F the car can go into limp mode (reduced power) to protect itself.
Will U059F fail an emissions test?
Yes, it can. U059F is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U059F to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. This is a job for a workshop.
Will U059F clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.