U05A2 code meaning
NOx Sensor B Received Invalid Data From ECM/PCM
Network system Generic code U05xx codes Check engine light
What U05A2 means
This is the downstream counterpart of U05A1: the tailpipe NOx sensor B finds the frames it gets from the engine controller missing or implausible and reports it. Ford's 2023 diesel summary documents it for the 3.0 L and 6.7 L engines next to P229E in the tailpipe NOx controller checks, using the same criteria as for the front sensor, an erroneous signal such as a dew point release with ignition off, or more than 1 s without a message, confirmed after 5 s. Ford's 2014 list also shows it with MIL. Because sensor B measures what leaves the SCR catalyst, the efficiency monitor cannot finish while the code is active. U059F describes the reverse problem, U029E a sensor that has gone quiet. A software update or bus repair usually comes before replacing the sensor.
U05A2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of U05A2
- Check engine light on
- SCR efficiency monitor incomplete
Common causes of U05A2
- PossibleDamaged harness to the rear sensor, exposed to road spray and heat
- PossibleEngine controller software sending implausible commands
- Less likelyFault inside the sensor B control unit
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Nox sensor bECM
What each part of U05A2 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A2 | The exact fault in that area. |
What to do next
- Note U05A2 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 U05A2
What does U05A2 mean?
U05A2 means "NOx Sensor B Received Invalid Data From ECM/PCM". This is the downstream counterpart of U05A1: the tailpipe NOx sensor B finds the frames it gets from the engine controller missing or implausible and reports it. It is a generic code, so it means the same on every make.
Is it safe to drive with U05A2?
Drive gently and only to a workshop. With U05A2 the car can go into limp mode (reduced power) to protect itself.
Will U05A2 fail an emissions test?
Yes, it can. U05A2 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 U05A2 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will U05A2 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.