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Discussion Starter #1
Is anything with computer (such as start, ect) needed to "Activate" or "enable" the sensor needed when replacing Throttle position sensor?

I am chasing down a problem in the drive by wire system. car falls flat on its face when I try to floor it, it just slowly accelerates, no redline.

Or are they plug and play
 

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1998 E320 base sedan @ 160kmiles
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The ECU is supposed to calibrate the TPS and pedal value sensor when you insert the key and turn to position 2 and wait for few minutes without starting the engine. You will hear a buzzing sound coming from the throttle postion actuator, indicating that the ECU is trying to calibrate. It may not succeed, and the differences between the TPS and pedal value sensor readings are beyond the thresholds values, you would have ECU fault codes.

I would check the MAF sensor. It is possible that it is not responding to sudden airflow changes.
 

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Discussion Starter #3
The ECU is supposed to calibrate the TPS and pedal value sensor when you insert the key and turn to position 2 and wait for few minutes without starting the engine. You will hear a buzzing sound coming from the throttle postion actuator, indicating that the ECU is trying to calibrate. It may not succeed, and the differences between the TPS and pedal value sensor readings are beyond the thresholds values, you would have ECU fault codes.

I would check the MAF sensor. It is possible that it is not responding to sudden airflow changes.
Mr Boca, you are wealth of knowledge.

You mentioned something I cannot figure out: is there another sensor on the pedal ? you mention "pedal value sensor readings." Any idea about this?

Thanks for tip about the MAF. Ill give it a clean. I already did tune up and plugs, albeit I had to re gap all 12 of them!
 

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1998 E320 base sedan @ 160kmiles
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Yeah, sensor B37 in in figure 17 in the attached link.
https://manual.startekinfo.com/manual/JSP/e4/9_3/m21.jsp

Note: You can get a better view if you click on the "printable version" on the right top side of the page, under the banner picture. When you press the gas pedal, it will change the values of two sensors (potentiometers). One goes up and the other goes down in terms of voltage readings to the ECU. The ECU compares these readings with the TPS sensor pair readings, and checks if they are plausible. It is kind of a servo mechanism, mimicking mechanical action of the gas wire moving the throttle plate.
 

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Discussion Starter #5 (Edited)
isnt that just the "throttle position sensor" that is cable driven off the accelerator? (figure b37)

or is there a seperate sensor? I dont see anything to be honest....
 

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Discussion Starter #7
wow thanks for clearing that up. looks like the TPS is on the throttle body . Thanks again.
 

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Discussion Starter #8 (Edited)
I replaced the throttle (very easy) with a new part. The old one was gunked up anyway. Putting car into position 2 and then pressing throttle down for 30 seconds helps calibrate it.

However, my car is still absolutely too slow. I am worried it is stuck in a limp mode. When I floor it, car is not able to redline. it accelerates very slow, like a grandma-mobile

anything else I should look at? I did the transmission reset (obviously replaced the plug, gasket, filter, fluids) and also replaced throttle, plugs, wires, pedal actuator.
 

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1998 E320 base sedan @ 160kmiles
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If the car is not able to accelerate as it should, this does not mean it is in limp mode. In the limp mode, the gear is usually locked to first, or second gear, so it should accelerate fine. I think you should invest in a scanner to look for some live engine data before throwing more money into it. This would allow you to check the MAF sensor values in idle and during acceleration, and higher rpms. Also you should be able to check the fuel trim values, as well as other parameters, and faults.
 

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Discussion Starter #10
thanks for the info. Would you recommend a specific scanner that has those monitoring parameters? Yes, I have read the threads, (but will re read them, about scanners), but last time I was a bit overwhelmed by which scanner does what and which one i actually need, that is why I am politely asking which model. If you could point me in right direction, would be appreciated.

If the car is not able to accelerate as it should, this does not mean it is in limp mode. In the limp mode, the gear is usually locked to first, or second gear, so it should accelerate fine. I think you should invest in a scanner to look for some live engine data before throwing more money into it. This would allow you to check the MAF sensor values in idle and during acceleration, and higher rpms. Also you should be able to check the fuel trim values, as well as other parameters, and faults.
 

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1998 E320 base sedan @ 160kmiles
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For a day-to-day use, I recommend BAFX with bluetooth interface (if you have an Android phone) or wi-fi interface for IPhone. I use Torque Pro with my Android phone.

https://www.amazon.com/BAFX-Products-Wireless-Bluetooth-Diagnostic/dp/B005NLQAHS/ref=sr_1_4?keywords=bafx&qid=1578593286&sr=8-4

It is permanently installed in the MB that my son drives. I also have a spare Android phone in the car with Torque Pro installed (he has Iphone), so if he has a fault problem he can read the code and tell me over the phone. The TorquePro app will access the Mode 6 data which can reveal very useful information.
 

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Discussion Starter #12
Mr Boca, I have given up on this issue for now. I did get codes ... (secondary air injection , and LOw sensor voltake for switch time calibration TID $03 cid $04 ) but they chase me down other rabbit holes.

May I ask your frank opinion about my decelleration issue? when I approach a stop the downshifts kick quite a bit. unless I brake violently when slowing down , the downshifts are very harsh. Would you recommend I address the conductor plate or solenoids in issues like this? I can get a valve body and conductor plate for about 100$ only
 

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1998 E320 base sedan @ 160kmiles
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If it is a transmission related issue, you need to be more specific in which gear the harshness is observed. Also, do you have problems in up-shifting too ? How about cruising ? Many things can cause the problem. If it is confirmed to be a transmission issue, it could be due to, from low transmission fluid level, loose / plugged filter to plugged command, regulating and shift control valves, clutch or separator plate issues.

Have a look at the attached, and check the symptoms you have against the ones listed. We then take it from there.

STAR TekInfo
 
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