bamaroxz

http://www.txdps.state.tx.us/vi/Misc...q_obdii.htm##1

What is OBDII?
On Board Diagnostics-Second Generation (OBDII) is a computerized system on 1996 and newer model year vehicles that monitors emissions-related components and systems for proper functionality. The OBDII utilizes an on board computer to test and monitor all the emissions-related components and systems of the vehicle.
This system is so sophisticated, it can detect malfunctioning components and systems before more serious failures occur and even before the driver of the vehicle becomes aware of a problem. The OBDII enables a vehicle owner to make cost-effective repairs before more costly damage is done to the vehicle.
OBDII testing uses a scan tool that plugs into the vehicle's computer and determines that the emission system and components are working properly. The test downloads stored information from the vehicle's computer to identify emission systems or components that are not working properly.
When an emissions control malfunction is detected, a dashboard light illuminates stating "Check Engine" or "Service Engine Soon." If the OBDII system detects a problem, a corresponding diagnostic trouble code (DTC) is stored in the computer's memory. Using an OBDII scan tool, a repair technician can quickly retrieve diagnostic codes from the vehicle computer and make necessary repairs before a more serious problem develops.

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What systems are checked during the OBDII test?
The On-Board Diagnostics (OBDII) emissions test for 1996 & newer vehicles consists of the following:
Check 1
Malfunction Indicator Lamp (MIL) or Service Engine Soon Light, Check Engine Light, Check Engine Symbol check
This is considered the bulb check portion of the test. The light must come on when the ignition is turned to the ON position and the light must go OFF when the engine is started. The inspector answers these two bulb check questions as either a PASS or FAIL. If the light is not working, the vehicle will FAIL the test, because the purpose of the light is to alert the driver of the vehicle that there is a problem with the OBDII system (exceeding emissions) and the vehicle needs to be diagnosed and repaired.
Check 2
MIL Command Status and Diagnostic Trouble Codes (DTC's) check
If the MIL command status is ON, then the vehicle's Powertrain Control Module (PCM) is commanding the MIL to turn ON, because a problem has been detected within the OBDII system and a DTC has been set.
For example, an engine misfire DTC - PO301. If the MIL command status is ON with a DTC set, the vehicle will fail. If the OBDII system is operating properly, the MIL command status will be OFF.
Check 3
OBDII (Non -Continuous) Readiness Monitors check
These monitors are like self checks of each emissions component (EGR, O2 sensor, etc) within the OBDII system. These non-continuous monitors are considered Ready until either DTC's have been cleared with a scan tool or if battery power has been disconnected, then the monitors will reset back to Not Ready.
In order to get the monitors set back to Ready, the vehicle must be driven through a drive cycle, which is a combination of city/highway driving for a set period of time. This drive cycle relearns the OBDII system and rechecks all of the emissions component's individual systems. As each system completes its own self test, the monitor will set back to Ready.
If a problem still exists in any of the individual systems, a DTC will set again once the monitor changes to Ready. If a vehicle has a MIL ON with a DTC set and the owner disconnects the battery to clear the light to try to pass the test, all the non-continuous monitors reset back to Not Ready and the vehicle now fails for Not Ready.
We allow two (2) non-continuous monitors to be Not Ready and still pass the test, but three (3) or more Not Ready's will cause the vehicle to fail.
There are three (3) continuous monitors that are always Ready: Misfire, Fuel System, and Comprehensive Components. If you look at your Vehicle Inspection Report (VIR), you will see the emissions monitors listed and their Ready/Not Ready status. If any of the non-continuous monitors say N/A (Not Available) or N/S (Not Supported), then there is no monitor for that system.
This information is illustrated in a "Ready or Not" poster displayed in all of the emissions testing stations as well as the Recognized Emissions Repair Facilities (RERF's).
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What are the advantages of OBDII testing?
OBDII testing is quicker than previous emissions tests. This test determines whether there is a malfunction and/or deterioration of the devices that control the exhaust-emissions level. It can lower repair costs by detecting and storing a code specific to the problem. The OBDII test should readily identify vehicle problems, thereby reducing repair time and costs. This will, in turn, contribute to lower vehicle exhaust emissions.
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Reasons your vehicle may have failed the OBDII test
•Catalytic Converter failure,
• Faulty gas cap,
• Fuel metering out of specification,
• Incorrect ignition timing,
• Inoperative injection system and/or thermostatic air cleaner,
• Mis-routed vacuum lines, and
• Faulty Positive Crankcase Ventilation (PCV) System or Exhaust Gas Recirculation (EGR) System.
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Transmission-related Diagnostic Trouble Code (DTC)
[font="arial, helvetica, sans-serif"][size=2]If your vehicle has a transmission-related Diagnostic Trouble Code (DTC), please read the important steps below and contact the Waiver Station in your area for more information.

Transmission DTC repairs can range from $1500 to $3000, although some types may be cheaper (e.g., a transmission speed sen

Joel5.0

There are '94 systems (EEC-V) that were OBD-II compliant....... '94+ Mustangs with a V6 engine as an example.

bamaroxz

Ya, I was looking for the OBDI and ran across this, so I hope this posts helps somebody. Mine is OBDI, still lookin for a good article in it. Thanks for the input JOEL5.0. Tryin to get mine "em-friendly" [:@]. I got busted [:@][:@][:@][:'(][:'(].

Joel5.0

Nah!.... don't feel like that man, I was just ADDING to the information you posted..... a little detail regarding our beloved Mustangs..... for the 5.0L though..... they were OBD-I. The ONLY 5.0L pushrod engine OBD-II setups will be found in '96+ Explorers and Mountaineers.

bamaroxz

NO Joel, I I didn't mean your input was a bad thing, I was thanking you for it. Sorry if it came across as smart eleck remark, it wasn't meant that way man. You have helped me out alot on this forum and I truelly appreciate it. The ugly faces were for me getting busted for a "bad" sticker. Cool man?