Not Ready For Testing

Not Ready For Testing.

This is a common problem that we deal with a couple times each week ,  usually the story goes something like this.

The car was due for inspection and the check engine light was on so it failed the emissions test. During the course of the repairs the codes get cleared and then the owner is told that they have to drive the vehicle for a while to try and get the car ready for its emissions test but it keeps coming up not ready. 

The OBDII emissions test is really carried out by the car every time that it is driven, all the states emission test does is collect the cars data as it reports if it passes or fails. When someone clears the codes they also clear all of the test results that make up the monitors that the state needs to see completed in order to know if the car is operating correctly or not. If all of the tests that make up a given monitor didn’t get to complete, then that monitor won’t be set to ready. When we have to deal with one of these situations, understanding what it takes to get given tests to run is very important because tests can be stopped from running because of the car’s operating environment failing to meet certain minimum criteria. One example of that could be if the ambient temperature was too low or too high or if the engine coolant temperature did not stay within the programming limits. Both of those would be considered blocking conditions where the tests are prevented from running because the results would be too unpredictable. There are other times where the vehicle might not have been driven long enough to ensure full system operating temperatures. Some of those aren’t even directly measured but are inferred by operating conditions such as the catalytic convertor temperature. The engineers use modeling to try and predict how hot the catalyst would be based on the way the vehicle was driven, then with a catalyst at that temperature, they measure the oxygen storage capability of the catalyst and write the testing tables for the vehicle’s computer to run.

Once we have confirmed that no blocking conditions are occurring, we then have to make sure that each test enable criteria is met. This is easy to do in some cases with a scripted drive cycle that most manufacturers publish, or it can be done with a scan tool as in Chrysler’s case where the scan tool displays the parameter limits and the vehicle just has to be driven within them for a period of time.

If a test fails and it’s a two trip test, you will find a trouble code but it is set in global mode seven and those are known as pending codes.  They have to fail twice in a row to turn into a confirmed code and cause the check engine light to come on.