Hey Car Pros,
My 1998 Saturn SL2 drive cycle is taking forever to reset. I recently had a module replaced in the transmission. And the codes reset. I have driven the car almost 200 miles and its still not ready for inspection. I tried to follow a drive cycle sequence with no luck. I don't want to type out the whole sequence but it started with turning on the AC and Rear defrost. Is it possible that I'm not going into closed loop and would that cause the drive cycle to not reset? If so how can a check if the car goes into closed loop? Is there a special sequence to follow? What else should I look for. I have seen some posts that say it should only take 50 miles. One I read said something about driving 50 miles before turning that car off. Thanks for any suggestions.
If you have a 96 or newer vehicle you have the OBD-II diagnostic system. This system is constantly monitoring the sensors and solenoids on the engine. If you have replaced the battery, disconnected the battery or cleared the codes after making a repair you will need to do what is called a "Driving Cycle". This will perform a diagnostic on all the systems the computer monitors. This cycle can be done in under fifteen minutes.
To perform an OBDII Driving cycle do the following: 1. 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.
The engine must be run for two and a half minutes with the air conditioner on maximum 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.
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.
4. 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.
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 at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
7. 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.
This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.
March, 9, 2011 AT 3:45 PM
This is the sequence I followed. I'm going to give it a couple more tries. Maybe I left the key on and heated up the O2 sensors or something. Is it possible that I'm not meeting the cold start criteria with engine temp and ambient air temp? Could a bad temp sensor or MAF sensor cause the ECM to recognize a cold start? I'll get back after I run the sequence a couple of times. Thanks.
March, 13, 2011 AT 8:40 PM
Just wanted to add to this answer it's very common for the coolant temp sensor's to fail on those cars when in doubt change them there only 10. It's screwed into the cylinder right below where the upper hose goes onto the head. There is a black wire and a yellow wire going to it. Also inspect the connector if it's corroded I would change it also. The way I always reset the monitors after making a repair and clearing the code's on that car is to drive it over 50 mile's without turning the key off. Also that car doesn't have a maf sensor it use's a map sensor. Please let us know how you make out.
March, 24, 2011 AT 3:53 PM
It did turn out to be the coolant temp sensor. I replaced the temp sensor and followed the cold start procedure. Drove the car for about six miles without turning the key off and the drive cycle reset with not problems. Thanks for the help.
March, 24, 2011 AT 4:38 PM
Your welcome glad to hear you got the car fixed that's what we like to hear please tell all your friend's about us.