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jeeper ... 3/11/2022

2008 Jeep Wrangler (JK) X 6 Cyl 3.80L


Failed emissions/OBD2 NOT READY

I have failed my emissions test 3 times due to the OBD2 "NOT READY". I have no indicator lights on my dash and the code readers can't seem to find a code. I have done 100-150 miles between tests as I was told to just drive it. No luck. I have had a mechanic and 3 different code readers test and all came up empty handed . Any ideas how to make the OBD2 "READY" or what the problem could be causing the OBD2 to be "NOT READY"

1 Answer


Jimm 3/11/2022

Try to disconnect the battery (both positive and negative connections), then - reset the PCM again and try driving the 50+ miles OBD calibration drive cycle.

A "drive cycle" is a pattern of driving which should cause the computer to perform all of its tests. Technically there is a very specific procedure to cause each test to be initiated. Some happen under load, some are dependent on temperature, some on throttle position, some on the amount of time you've been cruising at a particular speed, etc.

'NOT READY' means the Onboard Diagnostic System (OBD II) has NOT completed all of its self-test monitors that keep an eye on the performance of the emissions control systems. Depending on the year, make and model of your vehicle, there may be half a dozen or more OBD monitors that must have completed. A single or multiple "NOT READY" indications will prevent your vehicle from passing the emissions inspection.

To pass an OBD II plug-in emissions inspection test, all of the OBD monitors must have run and successfully completed with no faults found. This tells the emissions test computer that your vehicle is performing within emissions limits for your year, make and model, and that your vehicle is in compliance with the applicable emissions laws, and that your vehicle is not polluting.

The OBD system monitors some functions every time you drive your vehicle, but only checks other functions under certain driving or operating conditions. Some checks are "continuous" and are ongoing all the time. The continuous checks include:

Misfire Monitoring - to detect ignition and fuel related misfires that may cause emissions to increase and/or damage to the catalytic converter.

Fuel System Monitoring - to detect changes in fuel mixture that may cause emissions to increase.

Comprehensive Component Monitoring - to detect any major faults in engine sensors that may cause emissions to increase.

To perform an OBDII Driving cycle do the following: Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.

Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.

Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.


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