Engine failsafe program / throttle position sensor

[Thresher]

Folks, I could use some insight. My car is a 2001 model year 740iL, produced 4/2000...

This past week I saw both transmission failsafe and engine failsafe warnings appear on my instrument cluster. I have the Peake Research code reader and it reported "0F, 75, 77", which according to documentation it came with is decoded as follows:

0F - table for looking up next code values.
75 - throttle position sensors
77 - throttle position sensor 2

No other fault codes are present, and the check engine light is off.

Leading up to this, I replaced front brakes and rotors, and the windshield washer pump last weekend. Last Sunday night I took the car out and did the brake pad bed-in procedure which involves a number of braking & speeding up steps. That went well, but I noticed a low windshield washer fluid level warning was still on despite topping off. I get back home, shut off car, and come back a few minutes later (thinking maybe a second start would clear the warning?). Upon startup, the car immediately reported transmission failsafe. I do have a battery voltage tester and saw it was at 12 volts and climbing. Not sure if the bed-in procedure I was performing sucks power from the power-assisted braking. I decided to hook up my battery tender and let the battery recharge overnight.

Monday morning, car started up fine and only the washer fluid level warning remained on the instrument cluster. Battery voltage with car running was 14.1 volts. I checked for fault codes and found the throttle position sensor codes which I mentioned. I drove the car for a few days w/o issued and then Wednesday after lunch I started the engine and immediately I saw the engine failsafe warning on the instrument cluster. I turned off the car for a few minutes, turned it on, and instrument cluster was ok (except for the washer fluid warning). Drove to a nearby gas station; refueled; and returned to work. Later in the day I drove the car straight home. Checked for codes again and only the throttle position sensor codes were present. The engine failsafe warning only appeared once that day.

The alternator on my car is new (installed last November). The battery is just over a year old. In the 6 months that I have owned the car I have learned this car does suck power from the battery, and thus I have a battery tender which I hook up once a week for good measure.

I'm wondering if the continued speeding up and slowing down from the bed-in procedure threw the throttle position sensor out sequence (can it be reset?) or perhaps just exacerbated a throttle position sensor that was already failing.

My understanding is that the throttle position sensor is contained within the throttle body assembly (part #13541435959 as illustrated on realoem). The sensor itself doesn't appear to be serviceable (or is it?). Is the next step I should take to replace the throttle body assembly because it contains the throttle position sensor(s)? I understand that there may also be some sort of pedal position sensor for the accelerator pedal; is that another likely culprit? Should that be automatically replaced too?

I do have good mechanic who I trust, but he is backed up and not likely able to look at my car for at least a week or two. Replacement of the throttle body assembly seems straight-forward since it is toward the upper front of the engine and probably within the realm of my moderate repair skills.

Any advise is appreciated!

Thank you!

[Zoz740i]

I'm not an expert but willing to share from my experiences on the throttle. Easy to remove and replace but first you can try and remove and clean with throttle body cleaner sometimes gunk can cause problems also you can check to make sure the boot on the front of the throttle is fully connected and and the harness to the throttle is fully plugged in.There are way more guys and gals on here with far more knowledge about this than me someone will chime in with better into for you than not good luck

[Thresher]

I am circling back to my original post to cover what I did to address the issue (should have posted this a while back, but my how time flies!). I know that there are a handful of others on this forum that like me purchased their 7-series within the past year and may run into a similar issue. This isn't meant to be a step-by-step DIY, but rather a brain dump on how I dealt with the issue. For a good step-by-step, see the Bentley service manual for the 7-series.

Working with a basic code reader, I had originally pulled diagnostic codes for the throttle position sensors. My indy mechanic was quite busy when this all happened so I ended up going down the DIY path.

First, I decided to invest in a mid-range multi-system scanner; a big step up from the simple reader I had, but not as fancy as what my mechanic has. While not really necessary for this task, it was helpful that the new scanner confirmed the same problem, though it referred to the problem as the throttle potentiometer. Whether it is called the throttle position sensor or the throttle potentiometer they are apparently one in the same. My car is model year 2001, production 4/2000 with the M62 TU engine. The throttle housing assembly on my car is the EDK type. My research indicated that there were no end user serviceable parts inside the EDK housing. With that thought, the idea of cleaning the throttle body didn't seem like the best idea as the problem was sensor/potentiometer related. The throttle housing is pretty much bolt-on and easily accessible at the front of the engine. I ordered a new throttle housing; found a good write up in my Bentley service manual on how to replace and followed that. It all went smoothly.

For the initialization of the new throttle housing assembly, that is where things get a bit confusing. The Bentley manual said the throttle adaptions needed to be cleared by hooking up a DISplus, MoDiC, GT1 or equivalent scan tool. My mechanic told me there was a sequence that didn't require one of those tools. I found a publicly accessible online document from a tool manufacturer that outlines the sequence as follows (see page 41, link here) and confirmed what I had been told:

Turn ignition on for 10 seconds (don't start engine)
Turn ignition off for 10 seconds
Start the engine

That sequence worked for me and the car started up w/o issue. Car idled fine and my test drive around the neighborhood and then highways went smoothly. I suspect the different forms of advice for clearing the adaptations exists due to the various versions of the DME for the 7-series. What worked me may not work for someone with ADS-type throttle housing, etc... so, keep that in mind.

Mission accomplished!