How Strict is the Drive Cycle?

[littlex5]

Originally Posted by EODguy

Your voltage is showing 11v, BMW's hate low or fluctuating voltage. I realize your engine is not running but still....

@EODguy, I don't know why the OBDII data shows 11v. The new data looks normal now. I also checked it with my multimeter and got some normal results: engine off 12.23v; engine running 14.01v and 14.34v when more loads are on (rear defroster, A/C max, headlights).

By the way, would a faulty gas filler cap or vacuum leak cause the O2 monitor not ready?

[Qsilver7]

Originally Posted by littlex5

@Qsilver7, thanks for reposting the drive cycle chart. Could you help me understand the followings?

1. What does FTP stand for?

2. Does "customer drive cycle" mean...
a) customers following the specified drive cycle exactly?
b) customers following the specified drive cycle as closely as possible?
c) customers' normal driving?

1. FTP = Federal Test Protocol

2. Customer drive cycle means - "C"

A customer's drive cycle is what they may do under their normal daily driving route. This route or "cycle" may not create the conditions for all monitors to be tested...thus the FTP (federal test protocol) has its defined "FTP drive cycle" where all of the monitors should be tested within its defined criteria.

You'll discover reading through many threads on this topic where owners will mention that they drove for hours or over 100 miles etc and the monitors still aren't ready. And when you consider the last test (idle for 5 minutes IN GEAR)...how many examples of daily driving does that occur...unless you are stopped at a railroad crossing or REALLY long light? This is an example of a "customer's drive cycle" versus the "FTP drive cycle". The FTP drive cycle can be completed in approx 30 minutes of driving if there aren't any other underlying issues.

[wpoll]

Originally Posted by littlex5

@EODguy, I don't know why the OBDII data shows 11v. ...

If you check the battery voltage with the ignition on but engine off, it's normal to see below 12v - these things suck huge amounts of power when not running and will pull even a good battery down that far.

[littlex5]

Originally Posted by wpoll

If you check the battery voltage with the ignition on but engine off, it's normal to see below 12v - these things suck huge amounts of power when not running and will pull even a good battery down that far.

@wpoll, yeah, I think I pulled the data in the morning (showing 11v) right before cold start.

[littlex5]

Originally Posted by Qsilver7

The FTP drive cycle can be completed in approx 30 minutes of driving if there aren't any other underlying issues.

@Qsilver7, thanks for the clarification...that helps a lot. You're right, even I had driven over 3,000 miles since battery replacement, I don't think I had done the 5 minute idle in gear process by chance.

It seems like FTP can only be done reliably by a shop on a dyno? I don't live somewhere that allows me to perform the specified drive cycle in one swoop. A service consultant at a local BMW service center told me that it does not have to be done continuously nor in the specified order. I've been trying different variations with no success. This is my realistic version of the FTP drive cycle...

1. Cold start for 2m10s (w/ headlights, A/C, rear defroster on)
2. Drive on local streets (stop/go) for a few minutes to a street without stop signs/stop lights
3. Drive ~22 mph for 3m15s
4. Drive on local streets (stop/go) for a few minutes to a freeway onramp
5. Drive ~55 mph for 15m
6. Exit freeway and coast to stop (with brakes) and idle for 5m

There are some questions that came to mind while going through the drive cycles...

1. For the specified idle and drive durations, how accurate do they need to be?
2. Can I use cruise control to maintain speed?
3. For the end of the 15m drive, when I coast to stop, can I apply the brakes?
4. For the end of the 5m idle, should I shut off the engine or drive off?
5. Is it possible that I have bad O2 sensors but not bad enough to trigger the check engine light?
6. Could vacuum leak cause the O2 monitor to be not ready?
7. Could a bad gas cap be a cause?
8. For future battery replacement, is it possible to connect another battery in paralley to preserve computer memory to prevent this from happening again?

[nick325xit 5spd]

To be clear, the drive cycle is designed to allow you to immediately test the car as quickly as possible.

Each segment of the drive cycle does not have to be connected, and you can do it separately.

It's also really important to have an OBD scanner to show you *which* I/M monitors are not ready.

Do NOT use cruise control. CC can use too large throttle inputs. It's better to let the speed drop than use more throttle.

I've found that setting the readiness monitors is very hard for people who have an abrupt driving style. My wife is never able to drive cycle her 993TT (notoriously difficult emissions cars), but I can do it consistently.

I have also found that driving at the LOWER end of the speed range works better for me.

All that said, if you can't set the readiness monitors with 3,000 miles of driving, you need to consider whether or not you have an issue that's preventing that. Knowing what monitors aren't setting would help.

Edit: I'm sorry, I missed the monitor readout earlier. Have you considered replacing the O2 sensors?

[littlex5]

Thanks for the info...especially not to use cruise control and stay at the lower end of the range...will try.

The O2 monitor and EVAP monitor are not ready. SMOG shop said they can let EVAP slide but O2 is needed.

I also suspect something is preventing the O2 monitor to set. I asked four different shops (including one dealership) and they all said nothing they can do when there's no check engine light.

[littlex5]

Turns out it was a loose O2 sensor. Thank you all for helping!

[X5chemist]

Originally Posted by littlex5

I also suspect something is preventing the O2 monitor to set. I asked four different shops (including one dealership) and they all said nothing they can do when there's no check engine light.

Yup, techs don't know how to troubleshoot anymore. If a computer won't tell them what's wrong, they don't know how or what to fix. I've fixed of a few after a shop couldn't find the problem.

Low voltage was a clue. Nice work tracking it down. Good luck! Mine is due for emissions checks in the next three months. Mine has to pass before the end of January for registration.

[nick325xit 5spd]

Originally Posted by X5chemist

Yup, techs don't know how to troubleshoot anymore. If a computer won't tell them what's wrong, they don't know how or what to fix. I've fixed of a few after a shop couldn't find the problem.

Low voltage was a clue. Nice work tracking it down. Good luck! Mine is due for emissions checks in the next three months. Mine has to pass before the end of January for registration.

Techs aren’t paid to troubleshoot. Customers won’t pay for the time. And even if a customer is willing to, flat rate means that they still get screwed.