Bench testing Carrera Idle Control Valve
 

Thougt I'd post howto bench test a Carrera Idle Control Valve (ICV). I came up with this quick bench testing procedure for these valves.

The center pin is the ground pin and the 2 outer pins are the signal, but the signal that comes from the ECM is a negative voltage -0v to -5v signal. So if you apply ground to the center pin and -5V to one of the outer pins the valve opens then switch the -5v to the other outer pin valve closes.

So you can simply Bench test this valve with a 9V battery (see attached pictures). To simulate the -5V signal you apply the '+' side of the 9Volt battery to the center pin and the '-' of the battery to one of the outer pins and then move the '-' to the other outer and the valve will open and close. I tested this on my valve, the 9volt battery is certainly more than 5V but has little current so you won't damage the valve. However NEVER try testing the ICV with 12V from the car it could (and most likely will) burn the valve and it will be toast!

I also have a fancier test if you have a variable voltage supply, you can apply the '+' to the center pin and the '-' to the outer then start bringing up the voltage from 0V to 5V as you increase the voltage the valve slowly opens, you can actually watch it. Then once fully opened, switch the '-' over to the other outer pin and once again start at 0V then slowly increase to 5V and watch the valve close. I tested this as well.

So there you have it a bench test for the ICV.

Once I get the car running I'll verify what the voltages are to the outer pins while the valve is operational as well as where the valve is parked when you jumber B&C.

Here are the pics:
http://forums.pelicanparts.com/uploa...1186442858.jpg

http://forums.pelicanparts.com/uploa...1186442875.jpg

Excellent write-up. Thank you.

excellent. thx

+1, this really helped me too. Provided additional confirmation of a bad ICV

I'm really glad this has helped folks. I spent sometime with one of these ICVs I took a good one completely apart to fully understand how it works and even measured voltage levels with it functioning in the car.

The 9volt simple test will tell you 98% of the time the health of the ICV. The next better test is to use a variable power supply 0-5volt instead of the 9Volt, if you have a 0-5volt supply you can actually move the valve open and closed very slowly and look/listen for stick points.

yes,..best to work with the actual operational ranges that would be used....variable supply.

great write up.,.,., down and dirty!!!!!!

Best,

Couldn't one buy a control/regulator at Radio shack place it on the + line?

Somewhere I read that the ICVs are controlled by pulse width modulation of the 5v and -5v signals. I guess that applying a variable voltage, 0- 5v fools the ICV into thinking that it is seeing 0-100% pulse width duty cycle.

REALLY good advice about NOT applying 12v! Thanks.

good question.. it would be nice to know if they are PWM control or straight DC control - I bet Sal knows.

might be able to test the ICV with just straight DC even if it is PWM driven... I don't know... I remember someone saying they make a buzzing sound..

The ICV is a very simple control, I have had one apart and internally it is just a simple DC Motor, the type with permanent magnets. The only thing is it can not spin because it has a internal stop so it turns in one direction hits the stop (fully closed) then can be reversed and it turns in the other direction about 360deg and hits the same stop on the other side (fully opened). The DME sends simple 0 to -5V DC to the outer pins to get it to turn the voltage is variable 0 to -5v

Applying voltage briefly will pin the motor one way or the other which made me initially think it acted as a duty cylcle device - but it doesn't. In actual operation it "hovers" partway open.
Someday when my car is running I'll have to scope it.
-Chris

I'll see if I can get some wires on mine... and then get the mobile scope on it. Do the wires go to the DME? If so I can use my breakout box... I have to go look if those signals go up there.. or at least a signal that makes sense to look at.

You might be able to back probe it at the connector (remove the rubber boot on the connector and push scope probes in from the back).
Another way is to make a little breakout connector using a female 3 pin (Eagle Day sells them) and a hard to come by 3 pin male connector. You did save the connectors before you threw out those old speed and reference sensors right? ;)
-Chris

Will be replacing my Ref/Speed Sensors, PM me and I will mail you one ;)

ChrisBennet said:
"Applying voltage briefly will pin the motor one way or the other which made me initially think it acted as a duty cylcle device - but it doesn't. In actual operation it "hovers" partway open. Someday when my car is running I'll have to scope it."

And hcoles said:
"[ICVs] make a buzzing sound.."

The "hovering partway open" and "buzzing sound" indicate PWM control. 5v applied at 60% duty cycle is seen as 3v (that's probably oversimplified) by the device so it "hovers' at a point of equilibrium. A straight 5v (or -5v) is 100% duty cycle and fully opens (or closes) the device.

I see folks are determined to figure out this ICV control and how the DME signals the ICV. So I'll put in my details here:

First, my bench test was a quick dirty way to just check the ICV and I was never really sure just how the DME signals work, for example are the DME signals analog (0-5v variable) or are they somehow a duty cycle signal like the ones that fire the fuel injectors? I think this is the core of the question. After detailed look at the DME schematic and how the ICV is wired to the DME I have concluded that the answer MOST likely is it is a duty cycle signal. The control lines (2 of them) that goto the ICV from the DME are actualy Ground signals! Here is the schematic all marked up with my comments for explanation on my theroy of how it most likely works:

http://forums.pelicanparts.com/uploa...1201623158.jpg

First thing you notice is that pin #4 of the ICV is always HOT (12Volts) once the car is running. Pin 4 ALWAYS has 12v on it! This means that the 2 lines that goto the DME MUST work by going to Ground. Now we know from bench testing that 9Volt battery applied to the ICV drives it fully opened or closed. This leaves me with a funny feeling that the DME controll lines (pins 33 & 34) are pulsed GND signal lines. But they could also be variable 0-12V analog but I doubt it. Now couple in the fact that some folks have said that the valve BUZZES when it's working points to pulsed signal.

Next, how can we prove what these signals really are? Here is what I would do.
1. start the car let it warm up fully
2. once warm let it idle till idle is stable
3. pull the wire harness/connector from the ICV
4. The idle should stay right where it is so long as nothing changes, like load or air leak.
5. Now place a scope across the harness pins like this: use a 2 channel scope. Pin 4 (center pin) is always 12 volts so we really want to observe pins 3 & 5. So we scope pins 3 & 5 and see what we have.
6. Now if the car is still at a good idle, meaning the current idle matches the DME idle value, 880RPM for 86 Carrera or 800RPM for 84. If the idle is correct the DME should send NO signals to the ICV.
7. No introduce false air by removing a vacuum line or the oil cap. The idle will imidiately go up do to the false air and this should result in a signal seen on one of the ICV lines (pin 3 or 5). All the while the harness is dissconnected from the ICV because if you do this test with the ICV connected it would instantly correct the idle and the feedback loop would cut the signal and what we want is to keep the signal alive so we can really see it on the scope.
8. Then stop the false air leak and now lets drive the RPMs down by just applying load by turning on the headlights and heater blowers, this should be enough load via the alternator to drive the RPMs down and we should now see a signal on the other line of the ICV.

So, there you have what I think would be a good test.

If I get the time I will try this, I have a really good lab quality 2 channel scope. You could also try a simple volt meter as well.

Not 100% sure but my bet is this is a pulsed GND signal.

Also here is the test procedure from the DME Test Planning manual, this is the recomended in car testing for the ICV:

http://forums.pelicanparts.com/uploa...1201624640.jpg

Great stuff Sal, will be interesting to see your scope results.

Jon

"This leaves me with a funny feeling that the DME controll lines (pins 33 & 34) are pulsed GND signal lines."

Good guess!

"But they could also be variable 0-12V analog but I doubt it."

Bad guess!

Most make this issue more complicated than it really is,
i.e. just check that the valve is clean and most importantly
that each winding (from the center pin) is about 20 ohms.

A very simple operational test:
1. Remove valve and fully close the vane and re-install
the valve without connecting the connector.
2. Start the engine and it should idle at a low RPM.
3. Connect the connector. The idle should come up to
the normal RPM.
4. Stop the engine and remove the valve and fully open
the vane and re-install the valve without connecting the
connector.
5. Start the engine and it should idle at a high RPM.
6. Connect the connector. The idle should go down to
the normal RPM.

Simple!!!