U030A — Software Incompatibility With Evaporative Emission System Leak Detection Control Module

U030A points at evaporative emissions system. The standard definition names the system involved; which part inside it has actually failed is what the checks below establish, cheapest first.

Common causes

The cause is almost always one of a few things. Here they are — U030A rarely comes from anything outside this list:

• Fuel cap not sealing or the wrong cap fitted
• Cracked or perished breather hose
• Purge valve stuck open
• Charcoal canister split
• Leaking tank seal around the pump flange

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Refit the fuel cap firmly, clear the code and drive for a few days — a surprising share of these are the cap
2. Inspect the visible EVAP hoses for cracks and loose clamps
3. Command the purge valve with a scanner and listen for it clicking
4. Smoke-test the system if the simple checks find nothing — a small leak is very hard to see

That is what holds for U030A in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.