EGR Temperature Sensor trouble code

[Woot!]

I just got around to checking the trouble codes on my Q. The check engine light has been on since I got the thing and it bothers me.

I took pictures of the whole process of removing the ECU and getting the trouble codes so that other people don't have to go through what I did to get the thing out.

There is a screw above the ECU that is impossible to get out unless you take the glove box out and the other cover.

So I got the ECU code and it gave me the code "35". So I looked it up and it is "EGR Temperature Sensor". I did some searching for this and could not find anything so can someone please enlighten me on this? I don't even know what an EGR is LOL sorry I'm so stupid . Thanks for any help you can give.

[Q451990]

EGR=Exhaust Gas Recirulating valve. It's the flying-saucer looking thing near the back of the left bank of your engine near the brake booster. A faulty EGR code is more likely corroded connections on the EGR control solenoid valve, faulty vacuum hose, or carboned-up tube leading to the plenum.

The purpose of the EGR is to introduce exhaust gases into the intake at certain load levels (cruise) to slow combustion. It has the same effect as higher octane fuel, since exhaust gases dosen't burn as well as oxygen.

Long story short... push the valve up at idle. The engine should almost choke down... if not the valve is bad or something is clogged. If that works, feel the bottom of the valve while reving the engine (with the throttle cable cams)... you should feel it lift at flutter between certain RPMs... something like 1500 to 3000 rpm. If that doesn't happen look for the cause... either a vaccum leak or bad solenoid or bad connection to the solenoid.

Heath

[Q451990]

Another thought... you must have a "California" Q - otherwise you wouldn't get the code. "Federal" emissions Q's didn't have that sensor, at least in 1991. There's a possibility that your Q has a CA ECU in a Federal car for some reason, so it would throw the code since there's no signal?

Check the emissions sticker under the hood to see if it mentions "California" on it anywhere. To my knowledge the only parts differences were a different p/n catalyst number, a different ECU program, and the EGR temp. sensor.

Heath

[Woot!]

It's had an engine swap. Do you think it is possible that the new (used) engine was a California engine or vise versa? The car came from North Dakota and it was on it's second owner so I doubt it is a California car. I will check under the hood and see what I can find.

[Woot!]

OK, I just checked the stickers under the hood and I didn't see anything anywhere that had anything to do with California emissions. The engine could very well be a California engine, it came out of Salt Lake City, UT.

[Woot!]

Ok, I just took the car for a drive around the block and the check engine light is off . When I pulled the ECU codes does that just reset it? Or is the light just going to go back on after a few miles?

[Q451990]

If it's a CA car, with it's CA ECU - then it would be looking for the EGR Temp. sensor. If that wasn't transferred during the engine swap you'd get the code. If you pull the ECU again make a note of the part number and I can look it up to tell.

Heath

[Woot!]

Thanks for the help.

I haven't put the ECU back yet, I dont want to put it back until I can get the Check Engine light to stay off.

I just got the part # off of the ECU, here it is: A18 A32 P02.

There are some loose vacuum lines in the engine bay that I don't know where they go. Could that have anything to do with it?

[goody90q45]

I just got the part # off of the ECU, here it is: A18 A32 P02.

That's an ECU from a 90Q45 base with California emissions (from the complete list given to me by 3Q Jay).

I haven't put the ECU back yet, I dont want to put it back until I can get the Check Engine light to stay off.

There are some loose vacuum lines in the engine bay that I don't know where they go. Could that have anything to do with it?

You need to leave that ECU dangling for a few days and figure out where the loose vac hoses attach. These are definately one of the contributors to the CEL and the EGR code on the ECU.

The EGR doesn't start working until about 20 minutes of driving. This would explain why after you reset the ECU code it (the CEL) didn't come back right away. I'm assuming here that you started with a cold engine. If it's only the EGR throwing a code you may see the CEL go out (and come back on) on longer duration drives.

I had a similar issue when I bought my Q (capped off vac hose) and unfortunately there's no pat answer. I ended up reading posts until I understood all the components of the emissions system and then had to troubleshoot each one until I found the plugged hose.

[Woot!]

That's an ECU from a 90Q45 base with California emissions (from the complete list given to me by 3Q Jay).

I just checked the title and it says that it is a 1990 I thought it was a 91 when I bought it.

You need to leave that ECU dangling for a few days and figure out where the loose vac hoses attach. These are definately one of the contributors to the CEL and the EGR code on the ECU.

Will do

The EGR doesn't start working until about 20 minutes of driving. This would explain why after you reset the ECU code it (the CEL) didn't come back right away. I'm assuming here that you started with a cold engine. If it's only the EGR throwing a code you may see the CEL go out (and come back on) on longer duration drives.

I very rarely drive it for more than 5 min. at a time. After I drove it for a while last night it did end up coming back on .

I had a similar issue when I bought my Q (capped off vac hose) and unfortunately there's no pat answer. I ended up reading posts until I understood all the components of the emissions system and then had to troubleshoot each one until I found the plugged hose.

When they swapped the engine than they couldn't figure out where they went so they just capped them. I think there is 2 of them. What if the new (used) engine is not designed for California emissions than what would you have to do to the new engine to make it work right?

[Woot!]

I got some pictures; in th first picture I have the EGR Temp. Sensor circled right?

Second pic; What could that go to?

[Q451990]

That is the EGR Temp. Sensor. Make sure it's pluged in...

The other plug goes nowhere. It's a dummy plug for testing the timing - I think it's called "method b" in the service manual.

At least they moved the sensor to your new engine, assuming the replacement engine wasn't also a CA engine. No temp. sensor in the JDM engines.___

You might want to post pics. of your disconnected vacuum hoses. Also, have you tested your EGR valve function? I don't know if there's a different code for EGR function vs. the sensor, but your code could be due to the valve just not opening.

Heath

[Woot!]

Thanks Heath for the help. The other end to that sensor goes down into the engine somewhere...I will have to dig around and find it.

Do you think it is possible for the sensor to be bad?

Also does the ECU only pull one code at a time or will it give you all the trouble codes at the same time?

[Q451990]

Thanks Heath for the help. The other end to that sensor goes down into the engine somewhere...I will have to dig around and find it.

Do you think it is possible for the sensor to be bad?

Also does the ECU only pull one code at a time or will it give you all the trouble codes at the same time?

The EGR temp. sensor electrical connection's bracket is screwed to a flat spot on the leg of the plenum that feeds cylinder 8. You should see it right beside the transmission dipstick. I have no idea what the failure rate is for the sensor... I have never heard of one, but it could be bad. The FSM shows how to test it with an ohm meter and pan of boiling water.

From looking at the FSM last night, it appears that there are two separate codes for the EGR - one for EGR function, and one for the sensor itself. My guess is that the sensor code is based on either receiving or not receiving the correct resistance. Have you looked at all of this in the FSM?

And yes, the ECU should give you multiple codes.

Heath

[Woot!]

Update: I just followed the wire from the EGR temp. sensor and found that the end was just dangling down the side of the firewall, but I can't seem to find the end that it plugs in to, I looked everywhere around the transmission dipstick and around the #8 injector and can't find it.

Do you know where the other end goes so I can find it's source and follow it and find the end?

[Q451990]

The harness connector comes out of the firewall right behind the EGR valve (actually closest to the BPT valve) near the brake master cylinder. Among other things, it has the AAC valve connector, and the left bank O2 sensor connector there). I'm not entirely sure why they routed the wire all the way to the other side of the engine bay in a big loop... guess that's where they had a place to bolt it down. The harness side has an orange wire and a black wire.

Heath

[goody90q45]

The other end to that sensor goes down into the engine somewhere...I will have to dig around and find it.

I thought the connector end was mounted just about at the #8 plenum intake runner.

Do you think it is possible for the sensor to be bad?

The EGR temp sensor is easy to check. Heat a pan of water and measure the resistance with a voltmeter as the water temperature rises. Checking all the components of the EGR system is pretty straightforward and is outlined step-by-step in the FSM. I'm going to guess that you've got a lot of soot on the probe not allowing it to read properly.

You need to figure out where the two capped hoses go before the CEL will permanently go away.

[Woot!]

I did search around in the FSM, but it isn't very user friendly for us "soon to be mechanics".

The EGR temp sensor is easy to check. Heat a pan of water and measure the resistance with a voltmeter as the water temperature rises. Checking all the components of the EGR system is pretty straightforward and is outlined step-by-step in the FSM. I'm going to guess that you've got a lot of soot on the probe not allowing it to read properly.

You need to figure out where the two capped hoses go before the CEL will permanently go away.

Update: I just followed the wire from the EGR temp. sensor and found that the end was just dangling down the side of the firewall, but I can't seem to find the end that it plugs in to...

First things first, I've got to find out where the thing plugs into, I doubt there is anything wrong with the sensor other than it is not plugged in

[Woot!]

UPDATE: I still can't find the end where the EGR Temp. sensor plugs into, I will probably jack the car up and take a look under there and see if I can see it hanging down somewhere.

On the 2 loose Vacuum hoses, here are some pictures of what they are and where they come from. The first picture shows where the 2'nd picture is zoomed in on:



PS Sorry Wes, I didn't know this part of the forum existed. I will post my problems here in the future

[Q451990]

Here are a bunch of pics. for you to browse through. Dial up people... i'm sorry...

Here's a picture of essentially the same area you showed with the metal tube with nothing going to it. I'm sort of at a loss on this one, since there's nothing like that on mine. My best guess is that it's the tube that feeds coolant into the bottom of the throttle body. Coolant is circulated around there to tell the fast idle cam when the car is warmed up. That metal tube shouldn't be where it is, but maybe it's bent around somehow? I really don't know... Try pulling the screw out of the loose hose and see if coolant squirts out.

Pic. of the same area near the TPS, but before I removed the harness to get it out of the way.

Pic of the EGR temp sensor routing...

Pic of the solenoid that (i think) controls the charcoal canister... this is near the hose that's capped off on your car.

EGR temps sensor connector mounted in it's factory location.

These two pictures show where the harness splits out for the left bank O2 sensor, AAC Valve, and EGR Temp. Sensor.

Another pic I took

Modified by Q451990 at 10:43 PM 1/17/2008

Modified by Q451990 at 10:44 PM 1/17/2008
Modified by Q451990 at 10:46 PM 1/17/2008

[Woot!]

Thanks for the pics. The ones that you have stuff circled in; isn't that just a plug for one of the injectors?

I'm not sure what the other pictures were for; is it something to do with the 2 loose vacuum lines?

edit-

The cord that I circled; I think that is the one that goes from the EGR Temp. sensor. Where does it go?



edit- Fixed the link
Modified by Woot! at 8:49 PM 1/17/2008

[Q451990]

I posted the pics first, and then went back to add the captions.

Oh, and you have a bad throttle body gasket. It's basically paper, and it looks like the upper right corner is broken off.

Heath

[Q451990]

Thanks for the pics. The ones that you have stuff circled in; isn't that just a plug for one of the injectors?

No, it feeds the AAC Valve, left bank O2 sensor, and the EGR Temp Sensor. You should be able to follow it out and find one plug that isn't attached to anything, with an orange and black wire. That the one you plug in to your EGR Temp sensor.

]The cord that I circled; I think that is the one that goes from the EGR Temp. sensor. Where does it go?

That's the one coming from the sensor. You're looking for the other wire in that picture... the one that you can barely see the black and orange wire feeding the plug. That's where you'll plug in your EGR temp. sensor connector.

Heath

[Q451990]

Alright... after looking up a pic of a throttle body on eBay, I don't think your mystery tube is what I suggested earlier.



Maybe it's one of the vacuum tubes that goes to the EGR Control solenoid??

I hate to say it, but whoever did your engine swap got 90 to 95% there and gave up... now you get the fun of finishing the job!

Heath

[Woot!]

your mystery tube

There is actually 2 of them.

Circled and followed is the line that goes from the EGR Temp. Sensor right? I have the end to it the sensor its self but I am looking for the end that it plugs in to.

And a picture of mine:

Is this just another one of those test plugs?

[Q451990]

Alright... I think we're making progress! In this pic, the connector I circled in red is the connector coming from the temp sensor. I think the one I circled in yellow is the one that the EGR temp. sensor should be plugged in to!

Now the obvious question... what the heck is it plugged in to now? Check that and see if there's another EGR temp sensor dangling around by the firewall. If so, unplug it and plug it in to the one that's actually mounted to your plenum! If it's plugged in to something else, let me know what the color code is for the wires on it's mating connector.

Oh, and the other black plug must be a test connector... mine isn't hooked up to anything either.

Heath

[Q451990]

Found this pic... maybe it's your mystery tube, but bent somehow? I would pull the screw out of your plugged hose at idle and make sure it's not squirting coolant (doubtful). Assuming it's a vacuum hose, might as well try plugging it in to your mystery tube.

[Woot!]

OK, I traded the 2 places; the one in the red is the one that is coming from the EGR Temp. Sensor and the one in the yellow is the one that is left that we are going to figure out next.

Here are some pics of the cable. The cable circled in yellow is the same cable circled in yellow above. The cable circled in RED is another cable that runs along the same line as the one in yellow.

Following them down under the plenum:

Under the plenum: I can see the red one goes to a sensor that has something to do with the cooling system.

The yellow one goes over to another sensor (I don't know what it is either) and than I don't know where the other yellow one that splits off goes. Is this something else or should I still track it down?

[Q451990]

What color wires are coming out of the connector that you circled in yellow in the first pic?

The sensor under the plenum that is cooling related is the ECU temp. sensor, and I thikn the others are your knock sensors.

Heath

[Woot!]

Found this pic... maybe it's your mystery tube, but bent somehow? I would pull the screw out of your plugged hose at idle and make sure it's not squirting coolant (doubtful). Assuming it's a vacuum hose, might as well try plugging it in to your mystery tube.

That is around the throttle body somewhere.

Circled in yellow is the throttle body about the place where the tube is in your pic. Circled in Orange is the 2 "mystery tubes"; there is actually 2 side by side just one of them has a tube hooked onto it and the other is just open.

Circled in red is where the 2 mystery tubes are located: