Is EGR system dependent on ECT sensor??

[JusAlil4Banger]

Hello everyone.
My problem is with my EGR system. My egr is not working, so i tested the system yesterday, and egr valve, cvc valve, and control solenoid are all working properly. Its leading me to believe that the problem lies in the ECU, or the ect (engine coolant temp) sensor. And another thing is that my radiator fan is only coming on, when ignition is off. I know there are fan switches A and B as well as the ect sensor. My main question though, is if the ect sensor sends the message to the ecu to turn on the egr at a certain temp? Cause I've manually tested all the egr components, and they all work, but the egr is not operating, but it's not throwing a CEL either. So im thinking that it has something to do with the ect sensor, since my fan isnt working either? Any advice is greatly appreciated! Im at a brick wall

[JusAlil4Banger]

Oh, and one more question. Does anyone know about the radiator fan switches A and B?
As far as i know, switch A controls fans while ignition is on, and switch B controls the fan once ignition is shut off to cool down coolant? Shouldn't switch B be able to work when key is off, and switch A can only work when key is on? I think i may have crossed the plugs on switch A and B?

[reklipz]

How do you know that the system isn't operating, and what do you mean by that? Do you mean that the EGR solenoid is never receiving a signal to activate, and if so how did you determine this? If so, this could be a break in the signalling wires; a simple continuity check on the appropriate wires will tell you.

Otherwise, it's possible the EGR solenoid/valve are working fine, but the EGR ports are plugged. This goes back to my question of how do you know it isn't operating and what exactly you mean by that.

[reklipz]

Oh, and one more question. Does anyone know about the radiator fan switches A and B?
As far as i know, switch A controls fans while ignition is on, and switch B controls the fan once ignition is shut off to cool down coolant? Shouldn't switch B be able to work when key is off, and switch A can only work when key is on? I think i may have crossed the plugs on switch A and B?

It's been a while since I messed with it, but I believe one switch is for one of the fans (the "radiator fan"; passenger side) and the other is for the other fan ("the A/C fan"; driver side), both mounted on the radiator. There is also a diode that comes into the mix somewhere, and I believe it is specific to the A/C fan (being called the "A/C diode" if I remember correctly). I could be wrong here, though. I would have to reference a diagram, which you can do just as easily as myself. If you find and post the wiring diagram I'd be more than happy to help read it, though.

Lastly, the device that controls the switches is actually mounted underneath the dash on the passenger side in the cabin. It's called something like "fan control module" or "cooling fan timer" or similar. This is the device that reads the coolant temp sensors and turns the fans on and keeps them on after the engine is shut off.

[JusAlil4Banger]

Thanks for the info reklipz. With the egr system, I've already taken the entire manifold off, drilled out the egr ports, cleaned em very good, and tapped and re sealed them. I manually tested egr valve after that by removing the #16 hose and applying vacuum to it. The motor instantly stalls out. So i know the ports and valve are fine. It is like you said, the egr solenoid is not receiving the signal to open. But the weird part is, i never throw a CEL? so thats why im thinking it may be the ect sensor, or faulty ecu? I've thought about testing for continuity but dont know the system well enough to pick out the right wire. Oh yea, forgot to mention this is all on a jdm h22a swapped accord.

[JusAlil4Banger]

Any ideas?? Anyone know if egr can work without temp sensor?

[vh22accord]

How do you know that the system isn't operating, and what do you mean by that? Do you mean that the EGR solenoid is never receiving a signal to activate, and if so how did you determine this? If so, this could be a break in the signalling wires; a simple continuity check on the appropriate wires will tell you.

Otherwise, it's possible the EGR solenoid/valve are working fine, but the EGR ports are plugged. This goes back to my question of how do you know it isn't operating and what exactly you mean by that.

I have the same question. How do you know that the EGR is not working? Just Because you applied vacuum to the valve and the engine stalled does not mean that the valve is not working under load. Try hooking up a vacuum gauge to the #16 line and take the car for a drive and see if your getting vacuum .

[reklipz]

Any ideas?? Anyone know if egr can work without temp sensor?

I don't know the answer to this. My intuition tells me that the ECU would have to first read the temperature sensor in order to interpret it, which means that unless the ECU has a way to know that the temperature sensor is missing or bad (by being out of range or something I suppose), the operation of the EGR would happen regardless of the status of the temperature sensor. If the ECU could detect that the temp sensor was bad, that means it would be smart enough to turn on the CEL; it doesn't do that, so I assume it can't tell.

Now, it's possible that a bad or missing temperature sensor will alter the normal operation of the EGR, but only if the EGR operation is somehow dependent on the temperature. That can only be determined by analyzing the software running the ECU (or similar ECUs), or by simply knowing how EGR systems operate. If someone knew how they operated and saw this thread, they would have replied by now (unless they're a dick! but I think we're above that here...).

You can look at the wiring diagram to confirm / deny that there is nothing in the path of the control of the EGR except the ECU (i.e. no relays related to suspect things (the cooling circuitry) on the controlling wires other than power/ground and the ECU signal).

EDIT ----
I just realized that there is a CEL code for a bad water temperature sensor. All of the above is more or less worthless... Isn't reasoning fun?

That brings me to my next point... If there is no CEL being thrown for the temp sensor, why even bring it up? If you suspect it's bad, replace it; it's probably not that expensive.

EDIT Again ----
I think your cooling fan issue is not related to the temperature sensor. You can test the temperature sensor by submerging the sensor tip in boiling water and measuring the impedance (resistance). I did this while diagnosing my cooling fan issue. Fixing your cooling fan issue will answer your question, but read on...

Next, you said you applied vacuum to the EGR solenoid and the engine stalled. That doesn't make sense to me.

[JusAlil4Banger]

I have the same question. How do you know that the EGR is not working? Just Because you applied vacuum to the valve and the engine stalled does not mean that the valve is not working under load. Try hooking up a vacuum gauge to the #16 line and take the car for a drive and see if your getting vacuum .

When i said, i know it works cause i applied vacuum to #16 hose... i meant only that i know the valve and passages were operational. I did that test just to assure myself that egr ports were clear enough to operate.

I don't know the answer to this. My intuition tells me that the ECU would have to first read the temperature sensor in order to interpret it, which means that unless the ECU has a way to know that the temperature sensor is missing or bad (by being out of range or something I suppose), the operation of the EGR would happen regardless of the status of the temperature sensor. If the ECU could detect that the temp sensor was bad, that means it would be smart enough to turn on the CEL; it doesn't do that, so I assume it can't tell.

Now, it's possible that a bad or missing temperature sensor will alter the normal operation of the EGR, but only if the EGR operation is somehow dependent on the temperature. That can only be determined by analyzing the software running the ECU (or similar ECUs), or by simply knowing how EGR systems operate. If someone knew how they operated and saw this thread, they would have replied by now (unless they're a dick! but I think we're above that here...).

You can look at the wiring diagram to confirm / deny that there is nothing in the path of the control of the EGR except the ECU (i.e. no relays related to suspect things (the cooling circuitry) on the controlling wires other than power/ground and the ECU signal).

EDIT ----
I just realized that there is a CEL code for a bad water temperature sensor. All of the above is more or less worthless... Isn't reasoning fun?

That brings me to my next point... If there is no CEL being thrown for the temp sensor, why even bring it up? If you suspect it's bad, replace it; it's probably not that expensive.

EDIT Again ----
I think your cooling fan issue is not related to the temperature sensor. You can test the temperature sensor by submerging the sensor tip in boiling water and measuring the impedance (resistance). I did this while diagnosing my cooling fan issue. Fixing your cooling fan issue will answer your question, but read on...

Next, you said you applied vacuum to the EGR solenoid and the engine stalled. That doesn't make sense to me.

Yes, if you apply vacuum to the egr valve while motor is idling, and the egr ports are clear, the motor should hesitate and stall out cause its at too low of an rpm to handle the inert gas. If i applied vacuum at idle speed, and nothing happened, it would mean my egr ports are pretty clogged up.

The ECT (engine coolant temp) sensor, will throw a code 6, if its not detected. But being obd1, i don't think it'll throw a code for simply not functioning properly. Also, as far as i know, the ect sensor does not have anything to do with radiator fan control. The fan is controlled only by temp switches, A and B. That's why i was curious what all is actuated by the ect sensor. Im pretty sure the ect sensors only job is to send the temp report to the ecu, and i must know what the ecu does with this information! Lol

Anyways, I've come to the conclusion that i have had the connectors for fan switches A and B, crossed with eachother. Being that they're both identical, and both in the same area, i guess i missed it! So i switched them back around, and my rad fan is working properly now. I can also see the egr valve jumping up and down throughout the mid range rpm. Still got more testing to do though. I'm just confused at why i never throw a cel for egr? Oh, and i dont think i mentioned before that i started all this testing because i cant pass emissions testing. Im failing in hydrocarbons and NOx. The NOx is way high.... max is 490ppm and im at 2400ppm! So that led me to believe that the egr ports must be clogged. So thats how all this started. I never actually throw an egr code.. hmmm

[reklipz]

Awesome, thank for the detailed reply. My apologies for confusing the switches with the temperature sensor. Personally, I find it silly that the radiator fans are on a separate control circuitry, but I suppose that if you need to run the fans while the engine is off, and the ECU is controlled by that, the simplest way is to make it a separate circuit. With modern technology, I suspect _everything_ is ECU controlled.

Oh, and i dont think i mentioned before that i started all this testing because i cant pass emissions testing. Im failing in hydrocarbons and NOx. The NOx is way high.... max is 490ppm and im at 2400ppm! So that led me to believe that the egr ports must be clogged. So thats how all this started. I never actually throw an egr code.. hmmm

I would start looking for a different culprit, . Have you checked your O2 sensor? I suppose a bad MAP or IAT (intake air temperature) sensor, but you would probably notice strange idles if this was the case. Also, ensure that your ECU isn't giving you a "code 0," i.e. when you jump the connector to check the CEL, if there are no codes, the CEL should be on constant. If it's not, your ECU is bad. Simple check worth the time, but note that implication is only one way; if the light is on solid with no codes, that doesn't mean the ECU isn't bad.

[JusAlil4Banger]

Awesome, thank for the detailed reply. My apologies for confusing the switches with the temperature sensor. Personally, I find it silly that the radiator fans are on a separate control circuitry, but I suppose that if you need to run the fans while the engine is off, and the ECU is controlled by that, the simplest way is to make it a separate circuit. With modern technology, I suspect _everything_ is ECU controlled.



I would start looking for a different culprit, . Have you checked your O2 sensor? I suppose a bad MAP or IAT (intake air temperature) sensor, but you would probably notice strange idles if this was the case. Also, ensure that your ECU isn't giving you a "code 0," i.e. when you jump the connector to check the CEL, if there are no codes, the CEL should be on constant. If it's not, your ECU is bad. Simple check worth the time, but note that implication is only one way; if the light is on solid with no codes, that doesn't mean the ECU isn't bad.

Thanks roughing out this tough subject with me! Lol
My o2 sensor is only about 9 months/9k miles old. I bought the motor low mileage jdm with all the sensors in it. Have yet to really check on the manifold absolute pressure sensor and the intake air temperature sensor. Haven't really looked into any of that stuff too hard, cause i never have a cel. But if i never have a cel, and my emissions are that bad, then i got a weird problem! Hmmm..... lol viscous cycle!

[wed3k]

hook up a vac gauge to the egr solenoid and hang it on the windshield. drive around at low speeds and see if vacuum is being applied.

2400ppm looks like the egr system isn't even functioning and you already confirmed the operation of egr ports, that or the cat is totally dead.

mine were clogged and still were at 1100ppm's....the egr could still hesistate the motor.

don't worry about the ect sensor. the code is mainly for checking if the sensor or circuit is open. egr will most likely function in closed loop which is pretty much any time the CEL isn't on, 30 seconds after cold start-up and not in a WOT condition.

[JusAlil4Banger]

[QUOTE=wed3k;3087502]hook up a vac gauge to the egr solenoid and hang it on the windshield. drive around at low speeds and see if vacuum is being applied.

2400ppm looks like the egr system isn't even functioning and you already confirmed the operation of egr ports, that or the cat is totally dead.

mine were clogged and still were at 1100ppm's....the egr could still hesistate the motor.

don't worry about the ect sensor. the code is mainly for checking if the sensor or circuit is open. egr will most likely function in closed loop which is pretty much any time the CEL isn't on, 30 seconds after cold start-up and not in a WOT condition.[/QUOnot too familiar with the closed loop thing? What exactly is, closed loop?
And i would've been using the vacuum guage from the beginning, but i don't have the pleasure of owning one of those fancy tools... i would have just bought one, but i was just layed off two weeks ago! So im holding on to everything i got, for now. Of all the times to get layed off...

Also, could it be possible to have that high of a nitrogen oxide reading(2400ppm) if the egr was fully functional? I wonder if it's something else that im not aware of.
Like Reklipz said, look for another culprit.
I always run 89 octane, should i be running 91 because its a jdm motor? Higher compression?

[wed3k]

just focus on the nox for right now.

closed loop is when the ecu uses sensors for feedback instead of preset values. so if ect is cold then it wont enter into closed loop till it begins to see heat. o2, tps and rpm are probably the main three for a MAP based motor.