AWD - OBD2 Readiness (Drive Cycle) Success

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OBD2 Readiness (Drive Cycle) Success S70 1998

I've seen many posts about how hard it is to get OBD2 monitors ready for inspection and how outrageously expensive is to let the dealer do it. I haven't seen posts from ordinary owners who got it done without any tools other than an inexpensive OBD2 scanner.

I just succeeded with a 98 S70 nonturbo automatic (113K miles). This all started with a check engine light with codes P0133 and P0140, both related to O2 sensor readings. I replaced spark plugs, rotor, distributor cap, one vacuum elbow and the PCV system. I disconnected the battery to do the PCV job (a royal pain in its own right). After that, 6 of the 9 OBD2 monitors weren't "ready".

With apologies for the long post, here is what worked for me. There are two basic steps, flywheel adaptation (very easy) followed by two OBD2 drive cycles.
If you live in an urban area, this work is easier and more safely done late at night or early in the morning when traffic is light. Do not be discouraged if after 1 or 2 drive cycles your scanner shows no sign of progress. Give it another shot. Mine showed no progress at all after the first cycle, then a solid green light and all monitors "ready" after the second. You can do this!

A note of thanks to Klaus for helping me figure out the temperature bit!

Flywheel Adaptation
The flywheel status must be "ready" BEFORE you do a drive cycle trip.

Background: The engine computer monitors flywheel speed to detect misfires. But the computer has to be able to distinguish between a flywheel slowing down due to a misfire and a flywheel slowing down due to a change in throttle position. The flywheel adaptation run accomplishes this. The flywheel adaptation is needed when the computer "forgets" due to the battery being disconnected.

When you do the adaptation run it makes no difference how warm the engine is, how much fuel is in the tank, etc. Just do it.

How to perform a flywheel adaptation run
1. Drive the car in third gear at 3000 to 3500 RPM, then decelerate with foot completely off the gas pedal down to about 1000 RPM. Do not use the brake. This is best done on a level road or downhill. A long downhill is better. Do this a total of 8 times. You do not have to stop between runs, or turn off the engine, or anything like that.

Compared to the OBD2 drive cycle, flywheel adaptation is a piece of cake.

A successful flywheel adaptation can be verified with a Volvo System Tester, but I just assumed that 8 runs would be enough if everything is working normally.

Drive Cycle
(This is based on Volvo TSB bulletin number 25-19 dated 6-30-2004)

Drive Cycle Check List:
Note: pay special attention to item 3, especially about restarting the engine.
1. Fuel cap must be tight.
2. Fuel tank must be greater than 25% full and less than 75% full.
3. Crank the cold engine (temp needle on the bottom index mark). Let it idle until the needle just starts to move up. Turn off the engine. Raise the hood and touch the temperature sensor, located just below the thermostat. It should be warm to the touch but not hot. The official acceptable coolant temperature range is between 84°F and 122°F. I think the temperature gauge needle can be as high as the first index mark, but no higher. Now restart the engine. The reason for turning off the engine and then restarting it is that the temperature must be in the acceptable range when the engine is started.
4. A/C turned off.

Drive Cycle Driving Sequence (Also called a "Trip")
Note: Keep the pedal as steady as possible at all times; it is better for the speed and rpms to vary a little than to move the pedal. Steps 01 through 08 are done with the automatic transmission in Drive. When you stop the car (steps 02, 04, 06 and 08) keep it in drive with your foot on the brake as it idles.

01. Accelerate gradually and drive about 35 MPH (under 1800 RPM) for 6 minutes.

02. Stop the car and allow the engine to idle for 1-1/2 minutes.

03. Accelerate gradually and drive about 35 MPH (under 1800 RPM) for 6 minutes.

04. Stop the car and allow the engine to idle for 2-3 minutes.

05. Accelerate normally to about 51 MPH and keep the engine between 1800-2200 RPM for 5-6 minutes.

06. Stop the car and allow the engine to idle for 2-3 minutes.

07. Accelerate normally to about 51 MPH and keep the engine between 1800-2200 RPM for 5 minutes.

08. Stop the car and allow the engine to idle for 1-1/2 minutes.

Note: Steps 09 - 12 are done in 1st gear.

09. Accelerate the vehicle to 1800-2000 RPM and then coast to a stop.

10. Accelerate the vehicle to 1800-2000 RPM and then coast to a stop.

11. Accelerate the vehicle to 1800-2000 RPM and then coast to a stop.

12. Accelerate the vehicle to 1800-2000 RPM and then coast to a stop.

The drive cycle is complete. Use an OBD2 scanner to check monitors. It takes 2 drive cycles (sometimes more) for all monitors to run and become "ready". You must let the engine get cold between drive cycles.

 





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New OBD2 Readiness (Drive Cycle) Success [S70][1998]
posted by  samS70  on Fri Mar 19 02:05 CST 2010 >

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