Someone suggested people in this forum may be able to help. I just did a JDM swap and CKF bypass but the CRV will barely idle and its due to the IAC doing nothing. I have 2 IACs, both test good, both will raise the idle if I manually power the valve with a 9 volt. After finding this:





I replaced with a yard ECM and nothing has changed. I still get no response from the IAC. I do get near battery voltage at the connector. We have set the base idle and ignition advance per the manual and nothing has helped!

 

No one?

 

What is the vehicle application ??? Year, model, trim level and transmission would be helpful. A damaged ECU could certainly cause the issue, but you stated that another ECU made no change in the idle... suggesting the damage you photographed is not related. What is the ECU part number ???

More information opens the door for more members helping you. Help us help you.

 

Sorry, I assumed Honda ECM logic would be more or less the same across most models, then realized I didn't put the model year when I stated "CRV"...

2001 CRV, automatic, AWD. Ill have to try to find the "trim" level, is it listed on the title? Vin decode?

 

In this case, LX or EX is immaterial. Off topic, why did you do the "CKF bypass" wiring trick instead of moving your old oil pump, CKF sensor, crank timing gear and lower cover over to the new engine ??? Because it is easier ??? Have you considered the possibility that you may have made a mistake in the wiring near the ECU and actually damaged the ground wire for the IACV ??? Do you get a hard code for the IACV immediately (or almost immediately after start up) after you turn the key on ??? If so, you have a short/open in the IACV circuit... and since you have stated that the yel/blk wire does in fact have 12v+ at the plug, I would be looking at the ground wire (blk/blu) between the IACV and the ECU.

 

I was unaware of the extent of putting the CKF onto the JDM motor until we were ***** deep in swapping the drive train. The importer who supplied the setup made it sound like you just "swapped" the sensor its self over. Had I known ahead of time I would have bought a new pump housing and all the gaskets when I got the new timing belt and water pump kit.

I get no IAC codes unless I unplug the sensor for a period of time. The CKF bypass was done correctly as I can possibly tell and has successfully removed the CKF code. Also, the IAC issue was present BEFORE any CKF bypass was done. We originally thought the bypass was going to fix the IAC issue, it did not.

How would I be getting almost (11.5v) battery voltage at the IAC if I had a bad ground? I was measuring across the 2 IAC wires at the valve (plug disconnected).

 

BUMP!

 

Anyone???

 

With the engine running, unplug the IACV plug and listen for a change in the sound of the idle... then plug it back in and listen for a "thooonnnk" sound. You said using the pair of wires that you get nearly 12v+... this could mean that everything is fine wiring wise, but it could also mean that the blk/blu wire is shorting to ground. Check continuity between the ECU plug and IACV plug... the resistance should be super low... maybe 2-4 milli ohm. The ground should come and go as controlled by the ECU. If you check the voltage by placing your positive lead on the blk/yel wire and the negative lead on the neg battery post, you should have battery voltage. I firmly believe your focus however, should be on the blk/blu wire. You will have to trace it back to the ECU.

In the small chance that all of this checks out, remove the throttle body and IACV and verify the passage between the T/B and the IACV port is clear, and no gasket material is covering the hole.

 

I have completely disassembled and cleaned the throttle body and all passageways, which were all quite clean anyways. No RPM changes when you unplug the IAC. There is no sound when you plug it back in but there is a slight drop in RPS which appears to be electrical load to the alternator. Running a 9v battery to the IAC will result in the rpms jumping up like they are supposed too. If I "plug in" my second IAC but hold it in my hand an look inside it (tests "good" as well) leaving the other one installed on the intake, ("inoperable" as a vacuum plug), you can see absolutely ZERO plunger response as load and rpms change (when inducing stall). The engine currently only responds to RPM drop with fuel and timing which at least allows me to keep driving the truck (for now).

Are the IAC wires (engine harness side, plug) and ECU (plug at the ECU) side wires the same color or do they change as they are routed back through the harness?

 

This one stays the same - BLK / BLU at ECU connection.

I am pretty surprised none of the ECU repair guys have chimed in yet. Then again, some of them don't get on very often anymore.

I thought you told me you checked the wires before and everything was good? I can only give you advice, can't force you to use it... oh well.

.

 

I am getting ready to chase the wires but noticed "CIVIC ONLY" on connector "B" pins 6 and 15. There is a 3rd pin (23) that lists "IACV" but no "polarity" is listed?

Whats the deal?

 

Because certain Civics came with a 3-wire IACV. Your CRV did not, just troubleshoot B23 as listed. Most of your controlled things on the engine are done so via a variable ground (IACV, injectors, etc), so as long as one side has proper voltage (5v, 12v, 14v) then it may not (IACV) or may have an ouput (TPS, MAP, O2, etc). Pretty basic stuff.

 

Roger that, thnx!

 

Ok, PROBLEM SOLVED, but that is the SIMPLE explanation. The "HOW" is really complicated and weird!

Originally, as I stated in the first thread, when I was warned that you could plug multiple sensors/valves in, incorrectly, like the power steering line pressure plug and the IACV, WE CHECKED for this, REPEATEDLY. When we unplugged the sensor on the power steering line, that runs behind the engine, we got a POWER STEERING sensor SES code. When we unplugged the IACV we got an IACV valve trouble code. WE NEVER LOOKED AGAIN, as that was a simple confirmation the plugs where plugged into the correct sensors/valves.

That being said, when I set out tonight to ohm and continuity check the IACV wires, I noticed that the plug had a green wire and a black with silver tracer and I did not get continuity with the pin 23, so I looked closer. As others have stated one of the wires is supposed to be YELLOW. The plug, which previously set a POWER STEERING code, that was plugged into the power steering line had a YELLOW wire. I thought, if these plugs are REVERSED, as others have warned about, I'm going to be VERY unhappy, as we VERIFIED both of these previously. When I switched them, the IACV started working! FML! I have no explanation as to HOW the ECM would report an IACV issue, when you unplug the IACV, even though the IACV is plugged into the POWER STEERING sensor, but I can assure you it did, I even have pictures of the scan tool readout! The only thing I can even guess may have caused this is that maybe the ECM shorted right after the first time we started the JDM engine after the swap. Maybe having the plugs swapped between a driven valve (IACV), and a read only sensor (power steering line pressure) caused a back feed?

Here is the bigger issue, now that I KNOW the IACV is functioning, and it sets an IACV code INSTANTLY when un-plugged, I still need to verify that the power steering plug isn't reversed with anything else. What other sensors can use that same plug that are close enough to reach? What are their wire colors? Im worried now, due to the previous issue, and the ECM now shows signs of burned resistors in the same place as the first ECM, so I can't say I really trust the SES codes anymore. I was told there is 3 different sensors and/or valves close enough to get mixed up. I know where the IACV and Power steering sensor is, what is the 3rd sensor or valve?

That being stated, how IDOTIC is Honda for using the same exact plug on multiple different sensors/valves that are in close enough proximity to be mixed up???? I have never seen this before with ANY other manufacturer! In fact its COMMON PRACTICE to purposefully use NON-interchangeable plugs, and/or different COLORS, to eliminate this EXACT issue!

 

No, it makes sense since most of the time the ECU is just looking for a "connection" if you will and in this case will apply voltage/current as needed. Basically can go back to the old saying of garbage in, garbage out.

IIRC, The only other plug that could possibly reach would maybe be the IAT. The radiator fan switch has the same plug (IIRC) but the lead is extremely short and wouldn't come close to working. Well, you would REALLY have to try LOL, but connecting the thermostat ground (G101) would be impossible at that point. The IAT should follow the chart with a red/yellow and the other wire (going strictly off visual memory) may be a green/white wire??? IDK for sure right now.

While dumb for the common end user, it's actually pretty sweet for the guy who modifies. I can cut plugs from practically anywhere and spliice as needed. What I have gotten in the habit of no matter WHAT vehicle I am working on is either taking a sharpie or painters tape and labling every sensor as it is unplugged. This is especially true if it's going to be out for a while... but I have been messing with these cars long enough now I don't usually label Hondas anymore, just look at wires.

PS - Man, it sucks being right.

 

Ill check the IAT before i put another ECM in it.

Out of curiosity, can you give details on your turbo CRV setup? I had contemplated getting a 5 speed manual and putting a small turbo on it. How is the reliability of the drive train?

 

For stock engine "safe" power limits, the driveline is perfectly fine as is. The only problem you might see is blowing U-joints. See my thread I made for a little more insight on that.

 

I already have a prop shaft with replaceable U-joints. XD

How do I find said thread?

 

https://honda-tech.com/honda-element...rning-3258090/