Posted by Matthew Yu on Fri, Jan 15, 2010 @ 05:58 PM
The On-Board Diagnostics System Generation II (OBD-II) is a computer equipped on most 1996 and newer vehicles. The system monitors the performance of the ignition, fuel metering, emissions systems, including the sensors, and monitors the system itself while the vehicle is being driven to ensure that all components are working as it should be. The OBD-II computer has the ability to identify a problem well before the driver may recognize symptoms. Before a vehicle is brought in for an official Smog Check the technician will run what is called a Readiness Test that assess how well the vehicle's emissions system is functioning.
"Readiness Monitors" are indicators that demonstrate whether or not emission system components are being monitored by the OBD-II system. These monitors also report to the OBD-II computer as being "ready" or "not ready". If they are "not ready," they are not yet in a condition to determine if the associated emissions systems are working correctly. When a vehicle is taken to an emissions inspection station to receive the Smog Check, the first thing the testing equipment does is check these monitors. For model year vehicles 1996-2000, a vehicle with two monitors that are "not ready" will be accepted for the OBD-II test and the test can continue; for model year vehicles 2001 and newer, only one "not ready" monitor will be accepted for testing and the test can continue. Any vehicle that has more than the allowable number of "not ready" monitors will be rejected from testing until the monitors have been set to "ready" which may be accomplished by performing a drive cycle specific to the vehicle or with VW / Audi you can perform a Readiness Monitor Test with a scan tool.
Drive cycles are unique and vary between different makes and models, there is no generic Drive Cycle. Be sure to consult your manual or manufacturer for the specific drive cycle for your vehicle. Before you can begin a drive cycle you must check the status of the Readiness Monitors. Then check for diagnostic trouble codes (DTC), if any exist correct those faults, and clear the DTC's before beginning.
The status of all readiness monitors is reset to "Not Ready" :
-
Each time DTC's are cleared.
-
The battery is disconnected.
-
The ECM is disconnected.
The status of all readiness monitors is reset to
"Ready" :
-
After DTC's are cleared and the appropriate drive cycle(s) is successfully completed.
For example from www.alldatapro.com they have provided instructions for a 1998 Acura Integra LS Drive Cycle:
For most vehicles you MUST process the standard drive cycle for your vehicle make. There is the exception of VW / Audi where you can use a dealer level scan tools to elimate the lengthy process of physically driving your car to reset your Readiness Monitors. An example below is the Readiness Code chart to be processed with a scan tool with a screenshot from the Autoboss V30 / PC Max for a 2001 VW Jetta:
Completing the Drive Cycle successfully one time should reset most drive cycle monitors to a "Ready" status. However, there are times which require that the drive cycle be successfully completed two times, to achieve a "Ready" status. Furthermore, systems which use averaging, may require the drive cycle to be completed more than 2 times. It is necessary to perform only as much of the Drive Cycle as is necessary to reset the required monitors to a "Ready" status.