Code 1542 Causing Limp Mode

[mikehoy]

I'm a newby and have only owned my Z3 a few months and am having a real problem that I hope someone can lead me in the right direction. I have a 2000 2.3 which from what I have read here must have the M52TU engine. I can't get it out of limp mode and I bought a scanner and am getting code P1542 which shows to be a pedal or throttle position sensor code. As soon as I clear it and restart the car, it comes back. What do I need to replace or adjust. The throttle body appears to be way back underneath in a hard-to-get-to place. Any help appreciated.

Michael

[Ferris]

Well the good news is you don't have an electronic throttle so it's not the pedal sensor. The bad news is I think the posistion sensor is part of the throttle body and it looks to be integrated into the throttle body. The first thing you MAY want to try is to make sure the electrical connector to the throttle body is securely attached

[mikehoy]

I really can't hardly even see what's down there. You seem as though you may be referring to a schematic. I have nothing to give me an idea what to look for. Do you know of some visual aid I could locate?
Thanks.

[Jrdeamicis]

www.realoem.com go put all your car info in then search for the part. It will have diagrams.

[Akwon]

Just encountered this issue. Read something about needing to clean the throttle body, MAF, and checking out the slack in the cable. I adjusted the slack on the throttle body tonight, and reset the positioning of the throttle by turning the car off completely, turning key into 'on' position w/o starting, holding the gas pedal down, shutting the car off completely while still holding down the pedal for 20 seconds.

Seemed to do the trick for now. Any other shared insights by others on this forum would be appreciated!

[rf900rkw]

Let's set one thing straight here. The M52TU has an electronic throttle. Anyone that tries to claim otherwise has no concept of how the system operates.

The code you have is for the primary APPS out of range. This means it had a reading higher or lower than what is physically possible by design.

Adjusting the cable will do nothing.

Cleaning the mechanical throttle plate will do nothing.

Mashing on the gas, flipping the key, and stabbing the brakes three times will do nothing.

You either have a bad spot in the APPS, which will require replacingthe entire MDK, or (as was the case on my daughters 323) a bad spot in the wiring harness. She had a frayed wire inside the engine loom that was shorting on extremely rare occasions, often months apart. And only late at night in the most remote parts of the area. And of course it would fix itself as soon as I arrived. It took me over two years three MDKs and two DMEs before I managed to catch it in the act.

[Akwon]

Need some help. What is the APPS and MDK? Specific to your daughter's car, where exactly was the bad spot in the wiring harness? Maybe I can look at the same spot as well.

[rf900rkw]

MDK = The throttle body assembly. Motor Driven Throttle (as translated from German)


APPS = Accelerator Pedal Position Sensor. On the 'TU, it is built into the MDK. There is APPS1, APPS2, TPS1, and TPS2 all under the cover behind the cable wheel.

My short/chafing was right were the MDK wiring came out of the junction box bolted to the manifold. I had to open the box to find it.

[sydjai]

I have the P1542 code, often with P1180 and another O2 sensor one that I cant’ remember the number for. I have already replaced the MDK with a used unit off of eBay, and I am still getting the code. Finding this thread previously, I looked at the wires when I replaced the MDK and I could find nothing amiss. It was a PITA to get the wire box cover off, I made myself a little tool to release the clips. Anyway, changing the MDK fixed it for a few months, but now I get the error about every other time that I drive it. I turn it off, pop the hood, reach down to the mass of sensor wires under the MDK going into the box, wiggle them all around a little bit, get back in, hook up my code reader, reset the code, and all is good. (Until the next time it happens). Since I couldn’t find any chafing or bad spots the last time, I bought a used entire harness off of eBay. I have visually inspected the eBay harness and it looks good. So now to my question: How much of the engine do I have to remove to replace that harness? I’m pretty familiar with the sensors towards the front of the motor, (vanos, o2, oil, etc) but which are the ones on the rear of the motor? Do I have to take off the intake manifold? Can I even reach everything from the top, or do I need to do some from underneath? Any wisdom is appreciated!

[rf900rkw]

MAke sure the ground wire is connected to the throttle body. Since the orignial posts, I have had one other car that would glitch on rare occasions that was cured by reconnecting the ground wire.

[sydjai]

Randy-

Thanks for the tip on the ground wire—I haven’t pulled the trigger on the harness replacement yet, until I check into this ground wire possibility. My question is, where is the ground wire and where does it attach to the throttle body?
Here is a pic of my old MDK and the eBay harness. The only thing that makes sense is the stud where the electrical box connects to the MDK and then on the harness, there are two ring connectors, only one of which will fit on the stud on the MDK. On the car now, I know that neither of the ring connectors are attached to the MDK, but they are attached somewhere, as I can follow the wire out of the box but I can’t really see or feel where they attach. Are they on the starter? Should they be on the MDK? Thanks again for all your help!!
401478A1-B32C-4588-B12B-0533D5B737A1.jpg

[rf900rkw]

The two eyelets in your picture go to the starter. The ground wire is a stand-alone that goes down to a bolt on/near the oil filter tower. It's just a single black wire. It is on the stud for the loom mount, as you surmised. I don't like that position; too easy to get a loose connection. I put it on the forward lower housing mounting bolt.

[sydjai]

Randy thanks for the reply. I know that the ground wire is not hooked up right now, I will try to find it next time I am under the hood. Gonna suck this week, supposed to be 100 deg almost every day.