94 E320 electronic accelerator pedal actuator
 

Hello All

A problem developed with my wife's 94 E320 while at the cottage. I had my brother post to the forum last week (no internet at the cottage) and the comments came back that the problem described was likely the electronic accelerator pedal actuator. I left her my Jeep and drove the 320 back home (2+ hours) with no problems other than a noise (and vibration) best described as a dry bearing sound coming from the accelerator pedal actuator. Having looked through the CD this item has a DC motor in it so I guess that could be the noise. I am also getting error code 6, which confirms this system.

Questions:

The CD has limited info on the removal and replacement of the actuator any points to consider?

Are the units serviceable, or are rebuilt units available?

Brace me for the price of a new unit.

Thanks again,

John

Quick update:

Just finished removing the actuator. Not too difficult, just one or two awkward fittings, and the removal of a central valve box on the manifold to gain enough clearance to remove the actuator.

Now are these available rebuilt or just new?

Thanks,

John

If you got your code 6 from the DM , you now want to go see what is stored at the EA module..pin 14 on Diagnostic connector box.
That will have more specific EA module codes set..
A code 6 on DM can be something as simple as throttle decell sw to brake lamp sw....
Pin 14 will direct you to the specific detected faults of the EA system...

ONLY new, due to liability factor nobody would take that much risk rebuilding them!

Thanks Arthur for the next step.

Plugged the throttle actuator back in just in case its absence might screw up the readings.

Using the hand built led tester I got error codes 2 and 11 from pin 14 EA module.

From the code book:

Error 2 is - Closed throttle recognition signal to engine control module (HFM-SFI or Left LH-SFI)
Fuel safety shut-off to engine control module (HFM-SFI or left or right LH-SFI)

Error 11 is - EA/CC/ISC control module (N4/1) or Safety contact switch (M16/1s1) or Stop lamp
switch or Cruise control switch or Actual value potentiometer or Starter lock-out/back-up
lamp switch or engine speed signal or vehicle speed signal or closed throttle position
switch or safety relay in EA/CC/ISC control module

This vehicle has 160,000 KM, the neutral safety switch, ignition switch and some fuses were replaced recently to fix a no start problem. Further, in addition to the CEL being on, I do have a stop lamp indicator on, even though I believe all stop lamps are fine. This car still has the original harness.

The question is: is it the actuator or the control module? Remember the actuator is making grinding/squeaking noises when the ignition is on or the car is driving. I was thinking of opening up the actuator just to id the sound source and check for shorts.

Mercedes Canada quoted $1777.00 CDN for the actuator. Checking one other source.

Thanks again for any help,

John

Make sure there is a little slack in the cable ..
Erase codes and go back w/led tool in a day a recheck for codes..
Stop lamp sw is common on these...

OK, so it seems we are not certain the unit is bad. I have cleared the codes and will reinstall the actuator tomorrow, then drive the car and see what codes come up again.

I did however decide to open the unit up and the picture below shows the results. The noise was a dry bearing and some light machine oil has quieted the unit. Is it normal for the motor to run continuously with the ignition switch on?

Johnhttp://public.aci.on.ca/~jwells/actuator.jpg

Followup:

Put the old unit back in. Drove for 2 days. Drives fine, error code 2 on port 14 is the first to show up on day 2. The car drives fine, so I drove it to the cottage Friday night and about 1.5 hours into the journey, all acceleration is lost. I crawled allong the shoulder at 50KM/h for the next hour or so and make it to my destination.

I read the error codes on arrival and codes 2 and 11 now show (as before) on port 14. The motor in the actuator still runs with the ignition switched to on (which I don't think it used to but I'm not positive).

So what do you all think, is it the module controling the actuator or the actuator itself?

What about a used component given the price of new?

I will check later this week at a cafe for a possible answer, before I try and limp the car home.

Thanks for any assistance.

John

I do know that the throttle actuators fail for two reasons:

1. failing / deteriorating insualtion on the wiring on 1993-1995 models.

2. potentiometers that wear out over time.

Does the car have ASR?
You did not answer my posted last question on the cable slack..
This is very important for further diagnosis.

The cable allows the CTP-S/29-3 [ Closed Throttle Posistion Switch] to close at idle , notifying the actuator control module
of this condition..
If the cable is to tight , there is a chance the sw is ocassionally not closing . This will set a code and Cause the car
to enter LIMP MODE ..[ which is what I suspect you are in].
If one were to operate the throttle by hand from under the hood , the same thing will happen. You would start the car and find you were in Limp. That is why Service Manuals tell one to never attemp to give these gas by hand [ pedal only].
Where do you stand w/bowden adjustment???

Sorry for the delay in follow-up, but the car has been parked for the last week. After the last trip in limp home mode I was not looking forward to today’s return trip. But, no problem. The car performed fine for the full 2+ hours of the return; smooth idle and good acceleration. This is lots of fun; tracking down a suspect electric/electronic problem on a car with known bad wiring!

I had misunderstood the comment about the cable, thinking you were referring to the electrical cable. Dumb. So I checked the throttle cable this evening and there is about a ¼ inch of play in the cable and the various cams and stops seem to be fully contacting. As for the Bowden cable it too has a small amount of slack, and the transmission has been shifting fine so I don’t think it needs adjustment.

I do not believe the car has ASR but we have only owned it for a year or so. How can you tell?

I checked the codes, and 2 & 11 are still the only two error codes that appear.

Thanks Arthur for your help, but where to from here?