Gilly,
My MB factory Diagnostic Trouble Code (DTC) Reference Guide says that there is a 90% code for some cars, but unfortunately Richard was not courteous enough to include us in on what model he is talking about. Can't help someone if they rudly neglect to describe the year and model.

Take care,
Peter

Peter:
This is sort of like a continuation of a previous thread. Here it is:

http://www.peachparts.com/shopforum/tech-help/76935-bizzarro-overvoltage-relay-problem.html

It's an 85 190E, I assume that since it's a gasser, in 85 it must be a 2.3.

I'm sure he wasn't intentionally rude.

Gilly

Thanks Gilly,

Read the thread, and now I'm locked on and tracking. By the way good diagnostics and scenerio development on your part.

Peter

Peter:
Given that you now have all the info, what do you think of the fixed 90% reading he has?
Gilly

Gilly,
That thread is about ------69. I still have no clue what year and model Richard23 is talking about, and he is the one with the 90% reading.

Peter

Peter:
Sorry about this, I'm a little confused now. Based on this post:

I assumed you now knew that it's an 85 190E, assuming that since it's a gasser that it's a 2.3.

Gilly

Sorry for the delay in replying, I was out of town since Thurs. PM. I wasn't being rude, but yes, I should have identified the car early on in my question -the car is a 1987 300e, a non-Califormia car. I hope you can shed light on what the code means-I swapped in a new EHA & the code still appears. Thanks.

???
 

Did you guys read my response about the "implausible EHA current?" That is right off the CD in Section B, which covers the early cars.

Richard,

Now that we know what car we are working with, my MB factory diagnostic code book says the same thing for the 87 as Gilly's CD. 90% not used, however, the instructions for my Baum tool code reader say 90% means EHA current implausible. The factory code book says that code isn't use****il 1990. Im going to have to either pose this dilema ib the techs only section or phone the mavins at Baum tools. I''l have to get back to you. If the EHA answer works out, remember that the EHA doesn't generate current so swapping it is futile. You need to isolate the reasson the current sent to the EHA is not correct.

Peter

Chuck
Are you using the 201 chassis CD?

Gilly

Gilly -

No, used the 124. He said it was an '87 300E.

CT

power supply to O2 sensor
 

I was under the impression that it was powered by the fuel pump relay (if you open it you can see the 2 seperate relays).
The ovp supplys the power to the ecu meaning that even though the fuse on the ovp is blown the o2 sensor will still be getting power and sending a signal to the ecu, as will the air-flow meter and the coolant temp sensor. The ecu will not be able to adjust the mixture accordingly however as it is not powered up.
The Idle control solenoid and eha refer to a constant mixture setting.
That is my understanding.

Chuck
Here is the original thread, he never referred to it as a 300E

http://www.peachparts.com/shopforum/showthread.php?s=&threadid=76935

AF300E:
On some models (whenever they went to a heated O2 sensor), the fuel pump relay also activates the O2 sensor heater as directed by the engine control module.
If the OVP fuse blows and the engine control module is dead, the EHA is not powered at all and the fuel injection system is then in Fixed Operating Mode. There is no Lambda in Fixed Operating Mode. In fixed operating mode the engine control unit can be removed and placed in the trunk, and the O2 sensor is doing about the same amount of work as the spare tire.

Gilly

Gilly

Been following this thread and there seems to be some confusion over the type of car.

I believe in the above thread you referenced, the car is an '85 190E and the owner of the car is a different member - classic69.

Cheers.

Azhari

The whole first thread, as I see it, was started by Classic69 about his 85 201 chassis.

Nowhere in this thread (which was also started by classic69) or the previous thread, do I notice an owner with an 87 300E:

Richard28 has no car listed, and doesn't mention what car he has in this thread

Bud has a 91 300E

ctaylor has about 4 cars, none that is a 124

AF300E has some type of 124, no specifics

Peter (autozen) is just posting answers, no questions, and has no cars in his profile

so WHERE is the documentation that this is a 87 300E? On the previous thread? It's ALWAYs been a 201, 1985, which I believe narrows it down to a 2.3 by default, assuming it's a US spec car.

Gilly

ps: coffee time now:p