U05A8: Invalid Data Received From NOx Sensor C
A receiving module detected implausible data from NOx sensor C (smart sensor with own ECU). NOx concentration or pumping current values fail plausibility checks and are rejected.
What U05A8 means
U05A8 is a generic OBD-II network code in the invalid data & software group. In plain English: a module received data that didn’t make sense from the NOx Sensor C.
- Check engine light
- Usually on
- Emissions-related
- Yes — can fail inspection
- Limp mode possible
- Yes
- Drive cycle to clear
- Required
Get it fixed
Post this code once and get quotes from local mechanics. Free to post.
Makes the repair and parts links below specific to your car. Kept in this browser only.
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
- 01Module internal fault or sensor input driftMost likely
- 02Software version mismatch after replacementPossible
- 03Gateway module routing CAN messages incorrectlyLess likely
Can I drive with U05A8?
Not recommended beyond getting it to a shop.
This fault can put the engine or transmission in limp mode with reduced power, which can make merging and passing unsafe. Have it diagnosed as soon as possible.
Why we rate it urgent
- Can put the vehicle in limp mode (reduced power)
- Turns on the check engine light
- Emissions-related: will usually fail an OBD inspection
- Needs a drive cycle to confirm a repair
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose U05A8
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just U05A8. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for U059F, U059E. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Check module power, ground and the data bus
Confirm the module named in the code has battery voltage, ignition feed and a good ground. With the battery disconnected, a healthy CAN bus usually measures about 60 ohms between CAN-High and CAN-Low at the OBD port. Inspect connectors for corrosion and pushed-out pins.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Module internal fault or sensor input drift; software version mismatch after replacement; gateway module routing CAN messages incorrectly. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and complete a full drive cycle (cold start, idle, steady highway cruise, deceleration). The code is fixed when the related readiness monitor completes without it returning.
U05A8 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Usually a shop job
Needs a scan tool and some experience with testing.
Parts and systems involved
- NOx sensor C
U05A8 FAQ
What does U05A8 mean?
U05A8 means “Invalid Data Received From NOx Sensor C”. A receiving module detected implausible data from NOx sensor C (smart sensor with own ECU). NOx concentration or pumping current values fail plausibility checks and are rejected.
Is U05A8 serious? Can I keep driving?
We rate U05A8 as urgent severity. Not recommended beyond getting it to a shop. This fault can put the engine or transmission in limp mode with reduced power, which can make merging and passing unsafe. Have it diagnosed as soon as possible.
What causes U05A8?
The most common causes, from most to least likely: Module internal fault or sensor input drift; Software version mismatch after replacement; Gateway module routing CAN messages incorrectly. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix U05A8?
Typical labor is about $65–$375 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix U05A8 myself?
DIY difficulty is moderate. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will U05A8 clear itself?
Once the fault is fixed, the check engine light usually goes off by itself after the system passes its self-test over several drive cycles. Clearing the code with a scan tool resets readiness monitors, so an inspection station may turn you away until a full drive cycle is completed.