How to Check Readiness Monitors with a Foxwell NT520

If you've recently cleared a check engine light, replaced a battery, or are preparing for an emissions test, OBD-II readiness monitors are what stand between you and a passing grade. The Foxwell NT520 can read those monitors directly — but knowing what you're looking at matters just as much as knowing how to pull the data.

What Are OBD-II Readiness Monitors?

Readiness monitors are self-tests built into your vehicle's engine management system. They run automatically while you drive, checking that key emissions-related systems — like the catalytic converter, oxygen sensors, EGR system, and evaporative emissions system — are functioning within acceptable ranges.

Each monitor has one of three statuses:

When a monitor shows Incomplete, it usually means the vehicle hasn't been driven enough under the right conditions since the last reset — not necessarily that something is broken.

States that require emissions testing will typically fail a vehicle if too many monitors are incomplete, even if no warning lights are on. How many incomplete monitors are allowed varies by state and model year, so check your local requirements before heading in for an inspection.

What the Foxwell NT520 Does

The Foxwell NT520 is a professional-grade OBD-II scanner that goes beyond basic code reading. It supports manufacturer-specific diagnostics for a wide range of makes and allows you to view both generic (Mode $01) and manufacturer-specific live data — including readiness monitor status.

Unlike a basic code reader that only shows a pass/fail summary, the NT520 displays each monitor individually, so you can see exactly which systems are ready and which are still incomplete.

How to Check Readiness Monitors Step by Step

1. Connect the Scanner

Plug the NT520's OBD-II connector into your vehicle's diagnostic port, typically located under the dashboard on the driver's side. Turn your ignition to the "On" position (engine off is fine for this step, though some monitors only update with the engine running).

2. Power On and Navigate to the Right Menu

The NT520 will boot up and prompt you to select a vehicle. You can either:

• Use Auto Detect to let the scanner identify your vehicle automatically
• Manually select your make, model, and year

Once the vehicle is selected, go to the Diagnostics menu and select your engine or powertrain system.

3. Find the I/M Readiness or Readiness Monitor Function

Inside the diagnostic menu, look for options labeled:

• I/M Readiness
• Readiness Monitors
• Emission Readiness

The exact label depends on the vehicle make and the NT520's software version. On most menus, this sits within the Live Data or Special Functions section.

4. Read the Monitor Results

The scanner will display a list of monitored systems alongside their current status — typically shown as Ready, Not Ready, or N/A. 🔍

Common monitors you'll see listed include:

• Catalyst (CAT) — catalytic converter efficiency
• Heated Catalyst — on vehicles with secondary cats
• Evaporative System (EVAP) — fuel vapor containment
• Secondary Air System — smog pump or air injection
• O2 Sensor — upstream/downstream oxygen sensors
• O2 Sensor Heater — sensor warm-up circuit
• EGR System — exhaust gas recirculation
• Misfire — continuous monitor
• Fuel System — continuous monitor
• Comprehensive Component — continuous monitor

Continuous monitors run all the time. Non-continuous monitors only run under specific driving conditions.

5. Note Which Monitors Are Incomplete

If any non-continuous monitors show Not Ready, your vehicle needs a drive cycle — a specific pattern of city and highway driving that triggers those self-tests to run. The required drive cycle varies by manufacturer and sometimes by specific monitor.

What Affects Monitor Completion ⚠️

Several factors determine how quickly monitors complete:

• Battery disconnection or code clearing resets all monitors to Incomplete
• Cold starts vs. warm starts — some monitors require the engine to start cold
• Sustained highway speed — EVAP and catalyst monitors often need extended cruising
• Ambient temperature — some monitors won't run below certain temperatures
• Vehicle make and model — Ford, Toyota, Honda, and GM each have different drive cycle requirements

The NT520's vehicle-specific diagnostics can help here. Because it reads manufacturer data rather than just generic OBD-II data, it sometimes shows more granular status information than a basic scanner would.

The Part Only You Can Determine

Knowing your monitors are incomplete is straightforward. Knowing why they haven't completed — and whether a specific monitor failing to set after multiple drive cycles points to an underlying fault — depends on your vehicle's make, age, and condition.

A monitor that stays Incomplete after several proper drive cycles may indicate a real system problem, not just an incomplete reset. That distinction requires hands-on diagnosis. The NT520 gives you the data; interpreting what it means for your specific vehicle and whether you're ready for your state's emissions test is where your situation, your car, and your local rules all come into play. 🔧