#emissions
11 posts in Car Diagnostics blog about "emissions" — OBD-II diagnostics, DTC codes, repair. ← All posts
-
Euro 7 and on-board monitoring: what changes for owners
The next emissions standard adds continuous self-measurement, brake and tyre particulates, and battery durability. Here is what actually reaches the driver.
-
IUMPR: the ratio that proves your monitors actually run
A monitor that says "ready" once is not the same as a monitor that runs regularly. IUMPR is how the regulator closed that gap, and it is readable.
-
How the catalyst monitor decides your converter has failed
P0420 is a conclusion drawn from comparing two sensor traces. Understanding the comparison is what stops people buying converters they did not need.
-
Real driving emissions: why lab figures never matched your car
The gap between official figures and reality was not a rounding error. RDE testing exists because the old laboratory cycle could be engineered around.
-
Revs hang between shifts: emissions calibration, not a fault
Lift off to change gear and the revs stay up for a moment before falling. Almost every modern manual does it, and the reason is not what most people assume.
-
P0411 to P0414: secondary air injection flow and valve circuit
The system only runs for a minute after a cold start, which is why the fault is nearly invisible and the code arrives with no symptom at all.
-
P0421 and P0422: warm-up catalyst efficiency below threshold
A separate code for the close-coupled catalyst, and a separate meaning: this one is usually about how the engine behaves in the first minute, not about the converter.
-
P0441: EVAP incorrect purge flow — the valve that never opens
Not a leak code. This one says the purge valve is not moving the vapour it should, which is a different repair from every other EVAP code.
-
P0442: small EVAP leak — finding a hole you cannot see
P0442 means a leak around 1 mm across somewhere in the fuel vapour system. Guessing costs more than testing, and the fuel cap is innocent more often than the internet claims.
-
P0456: very small EVAP leak and the loose fuel cap myth
P0456 chases a hole around 0.5 mm across. It is the most frequently misdiagnosed emissions code on the road, and the fuel cap is responsible far less often than everyone assumes.
-
P0457: EVAP leak detected, fuel cap loose — the cheapest code there is
A code that names its own fix. Tighten the cap, drive for a few days, and it clears itself — unless the cap seal has hardened, which is the other half of the story.