emissions

Its time for inspections/emissions again(damn pa). anyway my check engine light was on and i had just recieved this car from my parenets caseu i off roaded my truck to death(bad rear main seal + water/mud = blown connecting rod).

it had like 110000 miles and i figuered the light was for the o2 sensors. So i replaced them and took it to the garage. The light never went out by itself but i wasnet really concered. He pulled the codes from it and it said that there was a hole bigger than .80" in my evap system and my engine was running lean. He cleared them and i drove around for a while. came back still had the evap but now the engine was running rich. He hooked it up to the computer and three monitors were not complete : o2 sensor, o2 heater, and evap system. WTF?

I pretty good with my cars mechanically. I know the gas cap wasnt loose. but as far as the evap problem i have no idea where to begin. and he said the upstream sensor was faulty, and i replaced both of them. Im going to go look at it as soon as i get off, hopefully the connector came uncliped, hopefully. Any help would be awesome.

-Tony

1999 Plymouth Breeze
2.4 straight 4 cyl
4 dr
automatic trans

I realize this is an old thread however; the diagnostic information regarding system monitor operation for OBDII equipped vehicles does not become outdated and may be of interest to others as well.

Any time that the OBDII trouble codes are reset, the computer requires that a specific drive cycle is accomplished to satisfy all of the monitors. Once a monitor has been completed, and a failure has been detected, it will turn on the “Service Engine Soon” light. There are several monitors and each one requires a different set of driving situations and conditions that must be met to satisfy each monitor. Some of the system monitors are completed immediately upon start up, while others may take up to two weeks to complete. For example: The EVAP monitor parameters may require the vehicle to complete up to 16 "cycles" (coolant temperature full cold to full hot), before it completes its test. In addition, it may also require holding a constant speed of 55 MPH for 5 minutes. Again, this is just an example of what might be included in its parameter. Each vehicle manufacturer has its own set of drive cycle parameters for each monitored system in each individual vehicle, year, make, model, engine and transmission. The point is that when the system is reset, there may be a malfunction that does not illuminate the “Service Engine Soon” light immediately.

Good information "oldmaster". I am but a grasshopper, but is there a way to find out for any particular sensor, what the parameters are that a particular model car is designed to test for? I realize it is firmware in the PCM, or whatever the manufacturer calls the computer of their particular car that monitors the sensors, but do they publish what those specs are?

Thank you,

Mike AKA grasshopper.

Mike,

When you ask about parameters for sensors: If you're referring to a range that they are capable of indicating, the answer is yes. For example: An ECT (Engine Coolant Temperature) sensor may have an operating range from -60F to +260F. This sensor incorporates a thermistor, (temperature affected resistor) and as coolant temperature changes, so does the resistance value through the thermistor. The ECM uses this data to determine coolant temperature. There are tables that show temperatures and what the resistance value should be for each degree. These tables are typically found in the shop service manual for the vehicle in question.

If you are referring to what the specific drive cycles are to satisfy each monitoring system, they also are typically found in the shop service manual for the vehicle in question.

These tables, or charts, will show values for all sensors on a particular vehicle. Possibly in a Google search, you might be able to find these tables on the web. If I haven’t answered your question satisfactorily, let me know.

Old Master (Chuck)