Help with Fault Code - PeachParts Mercedes-Benz Forum

Eiknujrac · #1 07-23-2004, 02:41 PM

I searched the forums but couldnt find the answer:

I used my home-brew LED tool to read the fault code off my 1991 300E, and came up with code 9 or "Current to Electro-hydraulic actuator". Does this mean my EHA is bad? Or does this mean that a sensor or something that sends the current is bad. I realize this code could be inconclusive to the problem, but i was hoping there was a common problem that made the engine throw this fault code.

Please help as I've just spent a lot of money on repairs and would like to be able to do this one myself if I only knew that the problem was.

THANKS!
-E

EDIT: Just replaced the oxygen sensor 100 miles ago, and have checked over the installation 100 times.

Eiknujrac · #2 07-23-2004, 06:18 PM

UPDATE: Sometimes the DM will also give me code 17 which is "Oxygen sensor Signal" (not code 5 which is just Oxygen Sensor), is this related?

THANKS!
-E

Eiknujrac · #3 07-23-2004, 07:13 PM

2nd Update: tested New oxygen sensor with voltmeter, and it showed .88v at idle and fluctuated when the throttle was depressed. (testing done when engine was just under 80C). Is this normal?

stevebfl · #4 07-23-2004, 08:00 PM

No, the EHA current is probably maxed out. You have a current code, what is the current? And what happens to the current when held at 2000 rpms?

Eiknujrac · #5 07-23-2004, 08:17 PM

I'm assuming you need a ampmeter to measure the EHA current, which i do not have. But i can get one.

Do you just unplug the EHA and use those leads to test the current?

Eiknujrac · #6 07-24-2004, 12:53 PM

Ok steve,

When i measured the current from the connector that connects to the EHA, i got 2.5 mA, or -2.4mA if the striped wire is the positive. (value stayed the same at 2000 RPM)

And when i tested the mA at pin 3 of the x11 on the drivers fender, i got -7.6 mA which fluctuated minutely between -7.5 and -7.8 and didn't change when held at 2000RPM.

EDIT: Is this the correct way to measure the current? I read your article but could not find exact wording on where to measure the EHA current, maybe i just didnt read it right.

THANKS!
-E

stevebfl · #7 07-24-2004, 02:10 PM

Current in any circuit can be read anywhere in the circuit. What you must remember is that you must place the ammeter into the circuit to read the current.

EHA current is done most easily by using a ready built harness which I don't remember the number for but can be found in the archives. I will explain a technique that could be used without harness: Remove connnector from the EHA, hook a wire from one terminal on the harness to the terminal on the EHA that it would connect to if the harness were plugged in. At this point you have an open circuit because the other side of the EHA is not hooked to anything. Now use the ammeter to bridge that open by placing one lead on the EHA and the other lead on the connector terminal that would be there if plugged in. In this position the circuit runs through the ammeter.

Now turn the key on, engine off and verify that you are reading +20ma. This is the key to verification of your hook-up. If the polarity is wrong either switch the ammeter leads or do the correction mentally.

You should not be reading 2ma with an O2 sensor pegged high. To verify lambda capability disconnect the O2 sensor EHA current should be 0ma. Ground the disconnected lead that goes to the controller (as opposed to the other side which goes to the sensor). The EHA current should slowly walk all the way to 12-13ma positive and stop. To test the other direction place one hand on that same lead and place your other hand on a 12v source. The EHA current should walk itself all the way to 12-13ma negative current. These values are constants and can help in viewing what is happening and as to whether you hook up is correct. BTW this last test can be done with the engine running and the correction in mixture will be evident in the way the engine runs.

Eiknujrac · #8 07-24-2004, 07:30 PM

With KOEO, and using a heavy gauge wire and test leads to close the EHA circuit, i still cant get above 3mA, and with the o2 sensor disconneted, i still read 2mA. I checked all my connections a million times, but maybe this is why it's throwing a CEL?

stevebfl · #9 07-24-2004, 07:45 PM

Try measuring the voltage across the two terminals of the EHA harness connector. I'm not sure what they should be, but there should be something.

Of course my first thought when there is no current is the OVP but of course that means MAS on a 91.

Also check your VOMs internal fuse and try measuring something else like the current to the idle valve which has similar connections. It should be much higher in the range of 600ma or more. Unfortunately if the KE controller is shut down the idle air valve will also have no current. and unfortunately both systems do rather well totally shut off.

Eiknujrac · #10 07-24-2004, 07:51 PM

Yes, no matter what i do, what hookup or length/guage of wire i use, i can not get a reading above 3.26 mA from the EHA hookup with KOEO. Anything that could be causing this?

Eiknujrac · #11 07-24-2004, 07:58 PM

Voltage from EHA connector was .5v, and does the engine have to be turned on for there to be current to the ICV? Because i measured no current with the KEOE, but i'm about to verify that after i post this.

stevebfl · #12 07-24-2004, 08:04 PM

Check the voltage across the idle valve connector, disconnected key on engine off. If you have no voltage there either you need to check power to the controller KE.

Eiknujrac · #13 07-24-2004, 08:06 PM

Voltage across the ICV connector was 2v, but still no current (multimeter showed .01 mA, but was just a flicker)

EDIT: how would i check the current to the KE Controller.

Eiknujrac · #14 07-24-2004, 08:30 PM

But if the KE controller was shut down, would i still be able to get the fault codes with the impulse counter from pin #3 on the data port near the battery?

stevebfl · #15 07-24-2004, 08:37 PM

I would have been happier with 0v. Verify your meter across the battery. I'm not sure what you shold see voltage wise cause current is the working element, but it looks like KE is out to lunch.

You need to get a wiring diagram and look at the powering circuit for the KE controller if all the above is accurate.