No acceleration,
09-09-2017, 07:35 PM
#1
No acceleration,
My 2003 G500 W463 started dying while driving. It seemed to happen only when the engine was warmed up. My OBDII reader gave a code for a faulty crankshaft position sensor. I had replaced it eight months ago, but I figured the new one must have failed, so i replaced it again. I also cleaned the MAF. Then it was running fine-for a day. Next day I started it, and there was no response when i pushed down the gas pedal. No acceleration at all. It would idle, and change idle speeds at random. This time the codes were P0120 and PO121, concerning problems with the throttle position sensor. I bought an identical used one from an ML500. I Installed it and then tested both of its circuits. The reference 5 volts was ok, and the readings from pins 4 and 5 looked ok, with the proper voltage range when turning the cable connector. However, still no acceleration of any kind! It just idles. I still get get the same P0120 error code as before. What is causing the lack of acceleration? Thanks for your help.
09-10-2017, 04:32 PM
#2
MBWorld Fanatic!
It does sound like the throttle position sensor. Was the used P/N the exact same as the P/N on the TPS you removed?
You really need to hook it up to a STAR unit to know for sure. OBDII readers are very incomplete for MB problem codes.
You really need to hook it up to a STAR unit to know for sure. OBDII readers are very incomplete for MB problem codes.
09-11-2017, 02:57 AM
#4
The part numbers are the same. Today i cleaned the throttle body. That did not help.
If the throttle position sensor has been replaced, but the code P0120 still comes up, then it must be caused by something else, but the computer thinks it is the throttle position sensor. The MAF, Intake air temp sensor, and MAP all send data regarding the air flow to the computer. But they all seem to be working. The throttle body has to open the butterfly valve when it gets the signal from the computer that the throttle position sensor says to accelerate. But obviously the throttle body is not being the valve. So maybe no signal is being received from the TPS, or no signal is being received by the throttle body actuator. Or the ECU is bad. But these all seem to be working when i test them. I am wondering if there is a short in the wiring, or a fuse problem. Has anyone else had this problem, replacing the TPS and still no acceleration?
If the throttle position sensor has been replaced, but the code P0120 still comes up, then it must be caused by something else, but the computer thinks it is the throttle position sensor. The MAF, Intake air temp sensor, and MAP all send data regarding the air flow to the computer. But they all seem to be working. The throttle body has to open the butterfly valve when it gets the signal from the computer that the throttle position sensor says to accelerate. But obviously the throttle body is not being the valve. So maybe no signal is being received from the TPS, or no signal is being received by the throttle body actuator. Or the ECU is bad. But these all seem to be working when i test them. I am wondering if there is a short in the wiring, or a fuse problem. Has anyone else had this problem, replacing the TPS and still no acceleration?
09-11-2017, 05:59 AM
#5
MBWorld Fanatic!
You really need to put a STAR unit on it. An OBDII sensor is not giving you sufficient or accurate information.
