Mercedes-Benz Forum banner

Changing the Cruise/idle speed module

3K views 17 replies 5 participants last post by  samosali 
#1 ·
Hi All,

Can I just swap the cruise/idle ECU with another one or is some reprogramming/resetting needed?

Cheers
 
#3 ·
The wiring for the throttle body was rotten so I've rewired that. Now the idle speed is 1200 when the engine is warm and cruise doesn't work at all (I don't know if the cruise worked before I did the rewiring).

I'm wondering if the throttle body wiring shorting together might have mucked up the ECU?

It would be good to borrow a good ECU from someone to check rather than shelling out £100+ for a second hand one.
 
#4 ·
rlambert, there are a number of things that affect cruise control. Different diameter tires, third brake light, brake light switch, dirty brake sensors are the most common. I bought a '97 CL600 about 15 months ago. The rear tires were larger than the fronts and "no" cruise control until I evened them out.
Anziani
 
#5 ·
Is there any easy way of identifying what is causing it, i.e. a fault code or is it trial and error to work out what the problem is?

I have put new rear tyres on but they are the same make and size as the fronts. Brakes seem to work ok

I do also have the idle speed problem. I tried the idle reset process detailed elsewhere but that isn't working so far.
 
#6 ·
Hi All,

Can I just swap the cruise/idle ECU with another one or is some reprogramming/resetting needed?

Cheers
please, please, fill your profile. I can only guess for which car the whole thing is about ... i remember that i have already answered to you but why can't you edit your profile? I can only guess that it is about 1994 S500 coupe ?
 
#7 ·
OK profile updated so the car now appears in my details on the left and yes I am asking about my S500.

I have been messing with the blink codes on the diagnostics and a few faults came up;

Pin 6 - ABS - Fault 13 - Brake lamp switch
Pin 7 - Cruise/Idle speed - Faults 2,3,6,11
Pin 8 - Base Module - Fault 9 - LH-SFI control module (N3/1) voltage supply, open circuit. Plus Faults 10,11,12,13
Pin 12 - Speed Sensitive Pwr Steering - Fault 4 - Right rear axle vehicle speed signal malfunction

I cleared the faults and went for a drive, the ABS works ok but the cruise still didn't work. I did check the faults again and the only one I still have is Pin 8, fault 9. Under the diagnostic information it gives a Test Step/Remedy which just says 23 -> 3.0 but I don't understand what that means. :frown
 
#8 ·
look at the attached file. i understand that you must check voltage between pins 78 and 65. these are pins no. 37 in first rpw and no. 24 in first row. with ignition on the voltage must be between 11 and 14 V. If not, wiring is broken.
 

Attachments

#10 ·
It's going to be next to impossible to test those voltages without the breakout/pass-through box that those test procedures require.
he can just put two wires between female and male pin. male pin is on the module, female pin is on the connector on the car. i did it several times. So put the wire without insulation into the corresponding female pin and then put module back. it is extremely easy and reliable.
 
#12 ·
I'll have to try this on my ADS module then!
just take let's say 1 m long thinnest wire (bunch of small wires with common diameter ca 1 mm including insulation ... i hope this is clear) and cut off insulation ca 1 cm at the end. twist (roll, wrench ...) this end to get small wires twisted = stronger. do not solder the wire because it will be too hard and there is not enough space for that. it is hard to me now to give you instructions how to put in (in the female connector) the wire but if you a practical person you will find out on you own.
 
#14 ·
Hi, the idle speed was ok before. When you take the actuator apart the gear wheels inside can move which is why I'm guessing it needs to reset itself.

I did notice that the car will run with the same slightly high idle speed even when the ECU has been taken out.
 
#16 ·
Hi,

I think this is where I need to do the idle speed reset process. The cold idle speed is fine and it is ok when in drive/reverse, just hot idle is high.

This is the reset process

Start and bring engine to normal temp, 80 deg C
-Stop engine and move ignition ke. CW to #2 position w/o starting engine
-Wait for basic training sequence/ protocol. ETA will hum, and ?ou will hear actuator clicking.
Wait for all sounds/noises to end complete
-Now, without turning key off, continue moving key C/W and start engine.
-Operate the vehicle for 30-40 minutes without turning off the engine, bring speed up to or over 65 mph if possible. Operate in a variety of conditions.
-Once time period is over, return to secure parking spot and park, DO NOT turn engine off... allow to idle for 15-20 minutes minimum!
-When time period is over, turn engine off.
-Congratulations, ?our ETA has been correctly put through the Mercedes Benz Engineering (Slang: Relearn)" Operational Sequence for 119 and 120 power plants.


Just as an update to what I been doing;

Checking the fault codes, for Pin 7 I had fault 6 which was the brake switch, I also had the ABS light come on and that was fault 13 on pin 6 which was also brake pedal switch. I replaced the switch as it was only £15 and the Pin 6 fault is clear and now on Pin 7 it is fault 2 which is saying there is a N4/3 control module issue
 
#17 ·
Ok, now fixed!!

It was the control unit. I found a guy not far from me with one so put that on.

Straight away the idle speed started behaving and the cruise also works as it should.

I suspect the control unit was damaged from the throttle body wires shorting together?

Thanks to everyone for their input.
 
  • Like
Reactions: samosali
#18 ·
cool. i guess in London one can get anything in a very short time. Once i was there with my motorbike and a spiral spring for gear lever broke. It was practically impossible to change gears and more than 1500 km to home. I found a guy in a telephone book (no internet in that time) and i got what i needed in one of his boxes in the yard. at London's technical museum (something like that) i have seen the same engine cut on half so i was able to study how to replace the spring. London has everything :).
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top