VEI OBD Readiness Monitor Fact Sheet - myAZcar.com

1 fact SHEETOn-Board Diagnostics (OBD) Readiness MonitorsAugust 2011 All 1996 and newer light-duty vehicles sold in theUnited States are equipped with On-Board Diagnosticsystems, known as OBD II. The primary purpose of thesesystems is to Monitor and evaluate the vehicle s emis-sions controls. Using this on-board evaluation, OBD helpsto maintain low emissions levels and notifies the vehicleoperator of problems before they become order for emissions systems to be properly evaluated,certain engine and transmission operating parametersmust be met before the diagnostics begin. This is thefunction of Readiness Monitors.

2 WHAT IS A Readiness Monitor ? A Monitor is not a physical device. It is a computerroutine (program) designed to determine if an emis-sion system is ready to be interrogated. Monitors arerequired to make certain that systems are notchecked that have not reached proper operatingtemperature or other parameters that could allowfalse MANY OF THESE MONITORS ARETHERE?All OBD II equipped vehicles have three continuous monitors. They are misfire, fuel trim and comprehensivecomponents checks system sensors and may use more distinctive names forsome addition, there are eight other non-continuous monitors for catalytic converter, EGR system, evap-orative emissions system, oxygen sensor system,oxygen sensor heater system, secondary air injection,air conditioning system, and heated catalyst.

3 Some ofthese monitors may be absent if the vehicle is notequipped with certain systems. WHAT CAUSES A Monitor TO BE NOTREADY ?When the vehicle diagnostic computer runs theevaluation routine, it is looking for specific conditionsprogrammed into the Monitor that tells the computerthat the monitored system is functional and at theprogrammed condition. If the system is not yet at thepredetermined conditions, the Monitor will register not ready. WHAT TRIGGERS A Monitor TO READY ? Once all the predetermined conditions have beenmet, the Monitor is triggered to report a ready condition for the system it is monitoring.

4 Reachingthese predetermined conditions is done using a set ofvehicle operating functions known as a drive cycle . In early systems, 1996-1999, the drive cycle was oftenvery simplistic, consisting of engine start, warm-up,local driving and highway driving. Newer models havemuch more detailed drive cycles, which have causedmany people to believe that certain monitors will notset to ready. This is untrue; it just requires a morethorough drive cycle A VEHICLE BE EMISSIONS TESTEDWITH NOT READY MONITORS? According to the Environmental ProtectionAgency guidelines, vehicles may not pass an OBD testif the monitors show the emissions system(s) to be not-ready.

5 A vehicle of model year 1996-2000 willbe rejected from testing if it is presented to a test sta-tion with more than two of the monitors reporting not-ready . Model year 2001 and newer vehiclesmay not have more than one not-ready vehicle that is rejected two consecutive times forhaving excessive monitors that are not-ready will notbe retested at the emission test station unless youcontact ADEQ first at the numbers listed IS THE Readiness OF THE MONITORSKNOWN?At emissions test stations and repair facilities, emis-sions systems are interrogated using a Scan Tool. This device can read the information stored in theon-board emissions computer.

6 The scan tool looks forPublication Number: FS 11-04the monitors first to determine if the systems areready to be tested. If too many monitors display anot-ready status, the vehicle will be rejected or THE HOME MECHANIC LOOK AT THESEMONITORS AND DETERMINE VEHICLEREADINESS?The method used to determine vehicle " Readiness "is to use a hand held scan tool designed for thatpurpose. Scan tools communicate with the vehicle'scomputer to determine the status of the is no other easy way to determine monitorreadiness. ADEQ recommends that you speak to atrained service technician about what should be doneto prepare for retesting your vehicle.

7 WHAT ELSE COULD BE WRONG?Troubleshooting the not-ready status of one ormore monitors should include looking for diagnostictrouble codes (DTCs) stored in the vehicle s this has not been done, or if the Check Engine light is on, scan for any remaining codes that arepresent. There may be emission related problemsremaining that have not been is good diagnostic practice to scan for DTCsfollowing any engine service, and following the failureof any monitors to reset. Remember that emissionssystems are complex, and correcting one problem(such as a stuck EGR valve) may cause a change inother emissions levels.

8 A code that did not show uppreviously may have been set during the drive cycle ,indicating a new, intermittent or remaining Monitor PROBLEMS COVERED BYWARRANTY?While the monitors are actually diagnostic programsdesigned to evaluate emissions systems on the vehicle,underlying problems or part failures may be coveredunder your vehicle s emissions warranty. Rememberthat the emissions warranty often extends beyond thevehicle comprehensive warranty. Always check yourowner s manual or your dealer for more CAN I GET MORE INFORMATION?ADEQ offers two Web sites that can provide mostof the information needed to find an inspectionstation, repair facility, test fees and much more: vehicle specific information, contact VehicleEmissions Inspection Program staff in Phoenix at (602)771-3950 or in Tucson at (520) 745-4536.