Try Rhinopower.org - the guy there has access to the Suzuki SDT and at one time was marketing a diagnostic interface and software that would let you see all the inputs to the ECU - I know it works well with the OBD1 versions, I'm not sure if it'll work with your OBD2 system.

If I recall correctly the software also has the ability to control specific outputs including the IAC valve - it's been awhile since I have used it.

If it works with your OBD2, it would certainly let you see what the ECU is seeing.

 

My old tool won't talk to a 1997 OBD2 model.
The IAC usually switches on the ground side so you should see a very small square wave signal, about 0.7V which is the voltage drop across the switching transistor. If its a battery powered scope then you can place it across the IAC which should give you a better signal. If the old IAC was short circuit then its possible that the drive transistor has blown. How many pins does the IAC have?
If you can get access to a Tech1 tool with a Suzuki cartridge then you can connect via the OBD1 interface which will give you the IAC duty cycle.

 

I found the ECU schematic on zuksoffroad:

http://www.zukioffroad.com/Tech_Library/pdf_documents/1_8L_engine_wiring.pdf

It shows the IAC as a two wire device so the diagnostic is pretty much as I stated above. The blue/black wire should be at battery voltage and the LT GN/BLK wire will switch at around 0.7V.

 

If you have a cell phone or tablet, you can access the ecu with an ELM327 OBDII dongle, The "Torque" app works well as a live DATA SCANNER..

Most Android units can use either the BT or WiFi dongle, Apple has a crippled BT so will only connect only VIA WiFi...

Besides the stand alone scanners, I use this setup,
Android Tablet (china..$56.00)
OBDII Dongle ( 12.00)
Torque Pro app (5.00, Torque free version $0.00)

.... Philip

 

Thanks. I have a PC-based OBD (OBD2) which doesn't seem to be up to the task but I really don't know what to look for. I sent an email to RhinoPower asking for his recommendation from his products.

 

This IAC is 2-pin and is switched to ground. I was looking for12v square wave, not 0.7v. With 4 shops messing with it, I wouldn't be surprised if the switching transistor isn't fried. That's where I'll look next.

 

Very helpful. Thank you.

 

I have a Samsung Android tablet. I found the dongle on Amazon. Where did you find the app? Is there a user's guide/manual available for it?

 

https://play.google.com/store/apps/details?id=org.prowl.torque&hl=en

May not do what you want as it is a monitor/diagnostic system, does not send activation/trigger signal..

But yes, you should be able to see the signal with a lab scope...

FWIW, snap-on/mac scanners are useless unless you have the specific key/module for the subject vehicle..

.... Philip

 

Some stupid untechnical questions, which may or may not be appropriate to the 1.8L:
Have you bench tested your IAC valve with 12vdc, to see if the plunger is vibrating properly?
Have you checked the wiring to the IAC?
Have you checked the idle switch in the throttle position sensor (or calibrated it) as I understand that if the TPS idle switch is no good, the IAC will not work properly.
Is your car throwing a code (check engine light on with the key on and off once the car starts)
Other than at idle, how does the car run? How does the car start from cold (cold idle), etc?

 

I don't think that the 1.8 has an idle switch but the TPS does not to be properly calibrated. The IAC doesn't actually vibrate when on an engine, it will move in and out by an amount proportional to the duty cycle, on the bench I would expect it to be either on or off.

If the IAC is maxed out then the signal will be either at 12V (0%) or 0V (100%) Can you reduce the air going into through the IAC?

 

I built device to replace the IAC which I could use to mimic the IAC manually with a screw. I can make an adapter to go between the IAC and the TB to limit the air but not increase it. The manual idle needle does not have much effect which makes me wonder if there is a blockage in the bypass?

All of the ideas in this discussion are good and I will start addressing them one-by-one.

 

Not sure if this is helpful, but found some interesting info in post #2 here:
http://www.suzuki-forums.com/suzuki-sidekick-escudo-vitara-geo-tracker/31709-idle-issue.html
If previous poster is correct, while there is no idle switch, the TPS does have input into the IAC not performing correctly, and can be tested and is adjustable.....????

 

Note that he gives two different voltages for the TPS adjustment.

 

True (.5v or 1.5v). But the concept itself may be of some value - testing the TPS?? Considering that thus for 3 or IAC's have provided similar problems??

 

I have not tested this IAC but the last shop says it's OK. I will do that today. Is there any danger of damaging it with 12v?
TPS was recently calibrated.
I plan to direct-wire the IAC to the ECU.
No codes, even if you unplug the IAC. Get code if unplug TPS.
Starts and runs fine. Idle cam comes into play when cold.
Mileage is low - 17mpg
Tailpipe was black when I got it. Replacing O2 sensor below manifold cleaned it up.

 

I am unfamiliar with the 1.8L TPS. However, the link above (which discusses the TPS relationship to the IAC) indicates that the concept of your TPS is similar to the 1.6L. While there is no idle switch, the TPS basically indicates to the ECU the position of your gas pedal. At idle (gas pedal not depressed), the voltage on your TPS should be 0.5v (not 1.5v as in one of the posts of the above link). As you depress the gas pedal, that voltage rises to about 4-5 volts at wide open throttle. This voltage is seen by testing the gray (TPS signal) wire to the gray/yellow (ground wire - wire color the same in the 1.6L, by the way). You then can check to see if this voltage moves up toward 5v as someone depresses the gas pedal (the key must be on, car not running). You need to backprobe the TPS connector in order to do this, as the connector must be connected. If your voltage does go up with the pedal depressed, you need to also confirm that it goes back to 0.5v once you let off of the gas pedal. I believe that if the ECU does not see this 0.5v, it does not think that you are idling. The link above advises that there is an adjustment screw on the 1.8L TPS (lucky you - however I have no idea where this adjusting screw is, being unfamiliar with this TPS). The idea being that the TPS must start at, and return to, 0.5v when the throttle pedal is not depressed. Some more info on this thread, as well:
http://www.suzuki-forums.com/suzuki...-sidekick-escudo-vitara-geo-tracker/54343-97-suzuki-sidekick-sport-1-8-a-2.html

 

The TPS is the same as that used in the 1.8 Baleno which also uses a Hitachi ECU, the spec for that is 0.5V+/-0.15V, measured at the ECU terminal. It may be possible to read ECU voltage from your scan tool, I don't recall whether that is an OBD1 only function, there is an OBD2 PID but it may not be mandated. You can slowly depress the throttle and check that TPS angle increases smoothly. If you can access the PID for relative throttle position then that should always start at 0degs, absolute throttle position will start at a higher value. Check that the throttle returns to the stop with a little slack on the cable.
Unfortunately most of the useful functions aren't OBD2 - IAC DC, Target Idle, Idle Position, RPM controls and electric load/AC status flags are all OBD1 only.
You can put 12V on the IAC for a few seconds to make sure that it switches.

 

I've had quite a few ECUs with a dead IAC driver, often they've come in for another fault and the owner wasn't aware that the IAC was faulty. I suspect that the first IAC burnt out and took the driver with it.

 

Presumably you have also confirmed that, as the throttle pedal moved downwards, the voltage increased without 'dead spots', etc, but coordinated with the movement of the pedal - and also, when you release the pedal, that it goes back to .5v. Anyway, it was worth a shot to see if this was a cause of your problem.

 

I appreciate that. I found several sources for repair/exchange of the ECU. I'm looking at a diagnosis, repair, functional check and warranty for $299 U.S. My only hesitation is the possibility that there is something I've overlooked.

Do you know what the RPM signal to the ECU is supposed to look like? Is it analog or digital? What is the source of the input? Is it the same as what the tach sees?

 

Sadly, I don't know the answer to any of your questions - the Sport is poorly supported, as there were not many of them sold. In the 1.6, the tach signal comes off the wiring at the noise suppressor, but whether the Sport is the same or not....??? Thus far, at least on this forum, there have not been many (actually, any) repairs that I've known of to the OBD2 computer (the older ones have had to replace capacitors, etc.) unless there was some occurrence of shorting wires or similar. Rhino (who is an expert in this) has previously spoken about the IAC driver being damaged in some way - have you opened up the ECU to actually look at the board/drivers to see if you notice any type of damage that would have occured from shorting wires - burn marks, etc.?? Often if faults occur this way, the damage is somewhat obvious - and then it might be possible to replace just the IAC driver - if that's where the damage is. Do you know what the model number of your ECU is? (Sorry, I haven't read through this post again). Rhino's theory about the there being a problem with the first IAC (which may have damaged wiring, etc) and thus the driver may have been fried, so that all the new IAC's exhibited the same problem, may very well be a good theory. I had a burned injector driver - it was quite visible when looking at the board.

 

Thanks again (and to Rhinoman) for the input. My exact next move is to get the ECU out and look for damage. (Not easy to get out because of no slack in the harness) I would expect the damage to be in the switching transistor rather in the driver since that's what interfaces with the IAC, but we'll see. Can't do it until after the weekend since we need the car right now.

 

Ta dah. Rhino should be able to give you info on those drivers - however, it will be a good idea for you to thoroughly check that wiring circuit, as whatever fried those drivers, if not repaired, will obviously fry the new ones as well.
Good advice about the difficulty of removing those connectors - note that they are practically impossible to find, so it is wise to take some extra time (with the locking tab, etc) and take them out carefully. It's also a good idea to have the negative battery cable removed before you start this disassembly, just in case.
Glad you found the source of your difficulty. Now, on to the repair!! Since you have the ECU out now, you should post the model number of it, so that it's easier to give you info on that specific ECU.

 

Please post a picture of the complete PCB so I can identify it.

 

Here they are. The top of board photo shows the burned resistors in the lower RH corner. The ground signal pin to the IAC is in the connector at the far top left (pin 23). That pin is in the third layer down to the far right of the connector. The upper ends of both resistors read near zero resistance to pin 23. The resistors both read 9.3 K-ohm across them.

The bottom of the board shows the heated area around the resistors which is in the cluster at the lower left just above the first mounting screw.

With the connector which carries the IAC ground signal disconnected at both ends, the two pins at the IAC read open (no short.)

Conclusions: The two burned resistors are in the IAC circuit and other components of that driver are probably damaged as well. There is no short in the harness between the IAC and the ECU. There must have been an open circuit in the original IAC (more likely than a short .) One of the mechanics who had a hand in it shorted the board output somehow. The other 2 "bad" IAC's were either mis-diagnosed or damaged in testing.

 

Just as an aside, it is good to 'study' before jumping into this - and with the internet, there is now no excuse not to do so. I brought my Tracker here from NY, when I moved here 18 years ago. When I had been here about 3 years or so, and before I found this forum and started learning the specifics about this car, my car wouldn't start - diagnostics indicated that it was the computer. In my desperation and haste, I found some guy in England who advised he could repair the computer - I was happy enough, as I was afraid that I would have had to trash my car. The FSM, of course, does not indicate anything about 'repair', only 'replace', which I was pretty ignorant about. Anyway, I sent the ECU over to England, and about a week later it was returned in working order - to the tune of about $300 (somewhat expensive for the replacement of $5 worth of capacitors). About a year later, I began to have the same problem - I pulled the ECU, and saw burn marks on the circuit board. This time, I found a replacement ECU (from California) for $100 core exchange. After waiting 2 weeks for the replacement, I plugged it in, the car started and then stalled again. As these replacement cores advise that the 'warranty' is voided if you open the unit, I never opened it, but sent the unit back for another replacement. And waited another 2 weeks. The same thing happened again. This time I opened the unit, and saw the burn marks in the same place - and that is when I found this forum. With due respect, Jerry diagnosed the problem for the forum - it wasn't the caps this time, but the injector driver. With his info, I found replacements, ran new injector wiring (rather than searching for the culprit that was continuing to cause the problem), had the new drivers soldered in at my local computer shop, and also installed a 5v fuse on the line, so that, if a wiring problem occurred again, the fuse, rather than the injector driver, would blow. So, a real learning experience - and my car is still on the road, thanks to the myriad of people on this forum who take the time to share their experience and information.
Hopefully your 'adventure' is over, and it has been a learning experience for you, as well.....

 

Even though I started repairing vehicles 65 years ago, this was my first encounter with an ECU. I was amazed to find (as you did) that there was no fuse protection on the board. Even though I thoroughly checked the run from the ECU to the IAC, I was very hesitant to hook it all up and connect the battery. It was quite a relief to discover that it didn't fry again (at least for now.) I understand that newer cars no longer have all of the functions on a central card and employ local modules for individual functions. (Could the designers be that smart?)

If I run into something like this in the future, the first thing I'll do is pretty much what I did here: Trace the damaged area of the board back to the connector pins so I know what control is involved. Then I'll know where to look for shorts or voltage that could have done the damage and correct that before I put a different board in.

Thanks again for the help.
Malcolm

 

I'm surprised that they couldn't repair that, maybe its more a case that they didn't want to spend the time on it or there was more damage than was evident.

 

While I do not know anything about this particular repair shop. I wonder if they have ever repaired anyone's ECU. $50 sounds like fairly good pay to open/close and send back an ECU. Sending back every ECU as "non-repairable" could make a good amount of money.... Scam?

Like I said, I have no information about THIS shop, but my mind works in odd ways.

 

There is a company in the UK who are quite well known who charge the equivalent of $190 whether they fix it or not. Personally I don't charge for testing but sometimes spend hours on a 'no fault found', I'm tempted to bring in a charge but I don't haven t make a living out of it and the majority of ECUs are faulty.
I do wonder if they have ever repaired a 1.8 Sidekick ECU, when I get in a 'new' ECU I have to make up a new harness to connect it to my tester and programme the tester with the correct cam and crank signals, that often takes longer than the repair and there is a cost involved, I can see how some could be tempted just to return it as unfixable.

 

Nice! It's always a good day when problems get resolved. If I were you, I'd me breaking out the soldering iron and replacing components to try to make it work!

But I'm a tinkerer.

 

I might take a closer look at it when I have the time. I think the biggest problem is that some traces were taken out so I'd have to do some patch wiring. I'd also not be too anxious to have it take out the IAC if it wasn't right.