560SL Idle Control Unit compatibility?

560SL Idle Control Unit compatibility?

Submitted by Thomas Herling on 02-03-2012

I have a 1987 560SL. I've been having high idle problems and after checking all other components, I'm pretty sure I need to replace the Idle Control Unit, Part #0065458532.

I have found several for sale at various places, but some are listed as being for a 560SEL. They have the same part number.

Would an SEL unit be compatible for an SL? Or are they somehow calibrated differently for the different models?


Don Kimbrough
Posted on 01-30-2014
High Idle

Have you resolved your problem?  I purchased a new throttle valve for my 1989 560 SL, installed it myself, but it not solve my problem.   Suggestions or recommendation would be greatly appreciated.

Thomas Herling
Posted on 03-14-2012
Hgh idle

My first try at solving the high idle problem was focused on the Idle Air Valve. After thoroughly cleaning it, it seemed to have solved the problem, but a few weeks later it was back to high idle hell.

I was able to get an Idle Control Unit that came off a 560SEL through eBay for about $25, and since I installed that I've had no further problems.

From what I've gathered, one common failure point on the ICU is one of the two transistors. Just for curiosity's sake I tried replacing both transistors on my old unit, but that didn't fix it.

One of the problems of trying to repair that unit is that it uses incredibly tiny surface mount components and almost microscopic circuit board traces, so I found it difficult to test many of the individual components on the unit.

There are quite a few threads on the various forum sites that address this issue since it seems it's a fairly common problem with the 107s.

Here's a good place to start, a systematic examination of the Idle Air Valve:

Posted on 02-04-2012
Any 560/420 ICU will do

Any 560/420 ICU will do Fine..:)

What diags/parts have you gone through thus far?  have you checked to see how many volts you are getting at the idle control valve when running?  How high is high?  Checked OVP?  Vacuum leaks?


Thomas Herling
Posted on 02-04-2012
re: ICU tests

Thanks for your response.

High idle happens after warmup, goes up around 1500 in park and neutral. It makes for an uncomfortably loud thunk going into reverse and drive. I can also feel the engine revving higher than normal while moving with my foot off the gas.

I've scoured many of the relevant pages on this forum and over at the BenzWorld forum for test procedures. I've checked the resistance and voltage to the Idle Air Slide Valve, took that off and thoroughly cleaned it with an ultrasonic, also checked the OVP, the temperature sensor, as well as voltage and continuity to the ICU. The "economy" gauge stays pinned to the left when the idle goes up--although I realize that's probably not the most accurate a test of vacuum leakage.

What makes me 90 percent certain it's the ICU is that, as one poster recommended, I've had the unit hanging out exposed from under the dash, and when I put a bit of pressure on the PC board the idle goes down to a more normal 600 or so. I had pulled the unit out and inspected for any obvious component damage and resoldered as many connections as I could to fix any cold solder joints. But it's got a daughter board that has surface mount components that are difficult to see, and the traces on that board are incredibly tiny, even with a 4X Optivisor. Also, some of the traces cross over others. So there may be a break in either one of the traces or one of those components has gone bad, but the design of that board makes it difficult to track down.

If the unit's pretty much compatible from one model to another, given that the part number's the same, that's great, because I've found a few used ones online for less than the rebuilt ones, and I'd like to first take a gamble on a used one for $50 or so rather than $250.

Tom Duncan
Posted on 03-14-2012
High Idle 86' 560SL

I have a similar problem. High idle occurs after driving when shifting to Park or Reverse. If I rev the engine, idle returns to normal. Did you ever determine if your problem was related to the idle control valve or the idle control modular unit? Hope you can offer some advise based on your experience.