Where is the Tachometer pinout location on 2001 CLK55
 

I need to find out where I can pick up the tachometer reading on a 2001 CLK55. I was told it was the pink wire on the third plug on the ECU from the right, bottom left hand corner. It did not seem to work.

I thought it might be under a different name, maybe crankshaft sensor XXX.

Thanks.

Try pin 13 on diagnostic socket x11/4. That is the TN signal.

Hi Steve,

I am not exactly sure where that is. Is it in the engine compartment?

Thank you.

My first impression is that anyone who is probing ECU wiring should be able to tell me where X11/4 is.

X11/4 is the 38pin diagnostic connector and it is under the oil cap looking cap on the electrical center at the right side hood hinge area.

Just what would you like to do with the engine speed signal "TN"?

LOL. I thought you would say that. My question might have give the impression I know more about the electrical system than I do.

I am installing a Split Second PSC1-001 unit to help massage my MAF signal. I was pegging out the unit and I am trying to get the voltage reading back on the map.

I need to pick up the Tach signal for this unit. It has a built in MAP sensor and uses the rpm range to figure how much more or less a percent of voltage should be sent to the ECU.

The tables work from vacuum to boost. My car was leaning out and this is the first step to fixing the problem.

Was that drivers side or passenger side btw. I think you mean the ECU box, but I want to make sure.

I'm pretty sure the 208 car has the connection on the passenger side. There should be a black plastic cap that comes off like a oil cap (90 deg twist and lift - don't turn it hard as the clips come out in the just released position).

BTW, I wasn't even sure such prepared signal was even available anymore, I had to look. The concept of engine speed is created in the ME controller from crank sensor input. In earlier days that signal would have been digested and sent as a square wave "TN" (engine speed) signal to other users. AC, ABS, Audio, Trans, were some of the other controllers wanting engine speed signals. Most late cars after 2000 (and earlier) digest the speed signal in the engine management controller and then spread the news digitally over the CAN network.

I found the #13 pin. It does give me a tach feed, but the results of the RPM's are not what I expected. I am reading higher RPM's than I actually have.

I was told by the engineer of this unit that they used a wire off of the second from the left ECU harness plug, but he did not have the specific wire. They worked with HPS on this unit.

Do you have the pinouts or wiring diagram for the ECU?

Could there be a different feed for the tach?

At least I know the unit is working, it just is not reading the correct RPM right now. It was changing the voltage to the ECU as I set it to.


Thank you for your help.

You are not understanding, there is no tach feed on that car. The engine speed is transmitted digitally to the instrument cluster.

If the equipment you are using needed a signal from a Mercedes of your year it would be looking for the "TN" signal. That is a squarewave pulse. I will put up a picture of what you are seeing.

#1 is crank angle
#2 is cylinder number
#3 is actual crank sensor signal
#4 is Cam sensor signal
#5 is engine speed signal "TN"

Thank you for the information. I will provide it to the tech for further explanation.

We just realized the cam signal was perfect to use. We just set the engine setting to a 1 cylinder 4 stroke and we have the correct rpm.

Thank you for supplying the image.

Chris