Hello everyone,

reading some articles here on code readers I decided to make one for myself. I had a look at a diagram posted here at some earlier stage and in half an hour the reader was done.

It also works as I found out a few minutes ago. I suppose the cache memory stores various codes at once. When I pressed the button to check for a code the LED flashed 8 times. When I pressed the button after that (no difference when I disconencted and re-connected the reader) the LED flashed 4 times. Then it flashed 2 times. Then it flashed 7 times. Pressing again - 11 times. That was all, after that the reader started flashing 8 times again.

Intriguing. Can it be that the cache stores all fault codes that appeared until it was re-set? I suppose that had the coolant temp sensor been faulty (for example) there would have been a code stored. Had the sensor been replaced in the meantime the code would still appear in the reader although the sensor would be functioning. Am I right? It would disappear only after re-setting the memory.

So now I am at loss whether the codes I have are actual codes or codes from previous things that went wrong but had been repaired in the meantime.

The question is: how can I re-set the memory so that all codes are cleared? I found no reference on that anywhere.

Thanks for your answers.

Sounds like you may have an OBDI vehicle. Year, make, and model would be helpful.

Disconnecting the battery for over 20 seconds will probably clear the failure codes.

It's in my profile. 300D 2.5 Turbo. 124.128. 8 pin connector. Will try to disconnect the battery and will let you know. Thanks.

OK I disconnected the battery but the codes are still there. Clearing of the cache isn't done by disconnecting the battery. I was suspicious already as I had my accumulator taken out and recharged some 2 months ago. Car was without battery overnight. That would have cleared the codes. I disconnected the cable from the idle control on a running engine some 2 years ago. That must have been one of the codes I am reading now. I doubt this has happened any time since the last battery recharge.

Besides, using an original code reader one only needs to select a function to reset the cache. No accumulator disconnecting takes place. There must be some other way to do this. Any ideas? I know one has to either short some of the pins or apply voltage to some pins or a combination thereof. Only if I knew which pins.

I don't take the codes seriously yet. One of the codes says my engine temp sensor is faulty. However I am certain the system can only tell (and store in memory) when the switch has either been shorted or disconnected. It doesn't tell whether the readings are accurate.

Hi Jassper

To clear error codes, do the following :
- hold push button 2-3 sec
- error code flashes
- wait 2-3 sec
- hold push button 6-8 sec
- wait 2-3 sec

Repeat the procedure for all the error codes. At the end, you should have a one flash code meaning that all codes were erased.

It can be done with engine running or not running : some codes are always there when engine is not running (those codes are not stored in memory and will clear themselves, e.g. EDS code 7).

EDS unit of 602.96 up to production date august 1991 will allways display error code 11 even if no fault exists (my 1992 is like that).

__________________
DR
1992 300D 2.5T 351 000 km

Hello!

Thanks for your reply. I have already found out about the clearing procedure - wait for the code to be displayed and then push the button for some 10 seconds. I have erased all codes but 7 and 11 which don't get erased no matter how I try. I have done this with engine off.

However if you say that 7 shows up when engine is not running and 11 is constantly present, then I suppose I have no problem at all.

Thanks a lot again.