How to diagnose engine codes 89 300e
 

Hey guys is it possible to diagnose an 89 300e, 3.0L inline 6 M103 ,without any special tools. I mean the engine codes, apparently theres lights i can count then look on a list for a specific problem. My engine light has come on and off a couple times. Can anyone walk me through the procedure

Should be lots of info in the archives about this. Search on diagnostic module. If your car comes equipped with it (I'm not sure USA versions had it in '89, only Calif versions), it'll be a small black plastic box like the one in photo below, mounted just to the right of the battery. Under the lid is a button and a red LED. With the ignition ON, motor OFF, push and hold the button 2-4 seconds. When you let up, the LED will flash a number of times. The chart below indicates what the flashes mean. If the LED flashes more than once, record the number and look it up. Then push and hold the button 2-4 seconds and the next code will be flashed, and so on until the first code is flashed once again, indicating that you are repeating the cycle. After each code is flashed, it can be erased from memore by pushing and holding the button 6-8 seconds.

Pulses
1 -- No fault in system
2 -- throttle valve switch, full load contact
3 -- Coolant temperature sensor
4 -- Air flow sensor position indicator
5 -- Oxygen sensor
6 -- Not assigned
7 -- TF signal
8 -- Altitude correction sensor
9 -- Electrohydraulic actuator
10 -- Throttle valve switch, idle speed contact

I believe the check engine light has to light and stay lit to pull any kind of codes...there aren't stored codes...at least in my 1990 300E that's the case....I have had service centers say that, yes, there may be latent error codes stored in the module but that's a all bullcrap......If you don't have a check engine light just figure it out...probably a tune up would work...that's what I did...worked great

Page # 23

http://www.geocities.com/MotorCity/Downs/1039/mercedes/cs1000_mb.pdf

If it's a Federal car as opposed to a California car, you won't need a scanner, only a DMM with a Duty Cycle scale. Connect to pin 3 of the round connector on the ignition control module located on the drivers side fender well, and to ground. Read the duty cycle with Key On Engine Off(KOEO) as I recall. If there is a code it will be one of ten codes indicated by 10%, 20%, 30%........ etc.

A very small amount of searching will turn up the key for these ten codes. It can be found on the factory service manual CD as well as this site via search.

Happy Hunting,
Larry

<If it's a Federal car as opposed to a California car,>

It should be a Cal car..

:bsflag:

Couldn't be further from the truth. The modules do store codes and the CE light is irrelevant - there can be lots of codes in the modules and the CE light won't ever come on. CIS is pin 3, MAS is pin 14 and the AC is pin 7. SRS is in there too, but I don't remember which pin. You can make your own "Arthur Dalton" code reader. Works great. If you have a CA car, the code reader is "built in."