EGR code 71 1994 fzj80 - cleaning temp sensor (1 Viewer)

[MoJ]

Taking tarbe's advice from the outing at Flat Nasty a few weeks ago I decided to clean the EGR temp sensor in hopes of resolving my CEL code 71. The temp sensor isn't as accessible on a 1994 as it is on 1995+. It's tucked under the EGR valve and is held by a 14mm nut. IIRC this is only applicable to all 1994's and California 93's as Non-CA 93's didn't have a temp sensor (someone correct me if I'm wrong).

(If you're confused which is the egr modulator and which is the valve they're labeled on the vacuum diagram under the hood.)

Getting to it is a little tricky. First remove the EGR modulator by slipping off the hoses and pulling it from the bracket. Second remove the bracket itself (one bolt). Next unplug the temp sensor and then figure out how to get a wrench on the 14mm nut. I used a stubby open end as the nut was positioned so that I otherwise couldn't get on it. Pull out the sensor and clean the tip with a wire brush or steel wool. Replace it all and pull the EFI fuse for a minute or two to reset the ECU.



So far I've gone through 4 start/run cycles of 10 miles each while traveling over 60 mph and the CEL has not returned. Prior to this it quickly returned each time after resetting the ECU so I've got my fingers crossed. As much carbon as it had on it I'm confident it couldn't of been working.

BEFORE

AFTER

 

[MoJ]

Just adding an update...

After about 4 months my code 71 returned.

I ran the factory tests and the valve and modulator checked out.

I removed the TB for cleaning and replaced the vac hoses. The hoses were clear and the ports in the TB were clean.

I removed the EGR VSV to test the resistance per the FSM. The FSM specifies a range of 30 to 34 ohms. Mine registered nada - completely open. Ordered a new VSV from C-Dan at it measured 33 ohms.

In fear of jinxing myself I won't claim victory just yet but I definitely isolated one bad component. So far so good.

And just in case you've always wondered what's inside your egr vsv...

 

[landtoy80]

Look at those tiny holes, it wouldn't take much to plug them.
Think of what hot exhaust gas would do to that diaphragm.

Up grade your modulator....yes, i have stock in the blue modulator company

 

[MoJ]

Look at those tiny holes, it wouldn't take much to plug them.
Think of what hot exhaust gas would do to that diaphragm.

Up grade your modulator....yes, i have stock in the blue modulator company

Yes, the holes are tiny. And the ports in the TB are even smaller. But none of them were dirty or clogged!

As easy as the mod is to monitor and replace I'm not worried about it until I see evidence it has failed. Point being there is no single component to point the finger at for egr codes.

 

[landtoy80]

I removed the EGR VSV to test the resistance per the FSM. The FSM specifies a range of 30 to 34 ohms. Mine registered nada - completely open. Ordered a new VSV from C-Dan at it measured 33 ohms.

Did you try blowing air through it and test again?

When testing the vsv, does the FSM call for ohm test only or do you test it with a battery and vacuun hose to see if it opens and closes?

 

[MoJ]

Did you try blowing air through it and test again?

Yes.

AFAIK the resistance reading can possibly have nothing to do with whether the mechanical portion of the valve is functioning correctly. I think the ohm reading is just to test the electromag portion which I imagine is just a wound piece of wire sealed in the plastic case. In my case I believe something went bad with the wound wire. Don't know for sure, just speculating as there's no way to access the wire without sawing into the casing which would likely damage the wire in the process. I'll speculate further and guess that you could entirely remove the mechanical portion of a working vsv and still get the correct resistance measurement just from the coil. Again, just speculating but if that is the case you could have a non-functioning vsv that tested out correctly when the resistance was measured - ie the mechanical portion was broke/clogged but the coil is still good. The coiled wire failing would explain how you can have an egr code without carbon contamination. Whaddya think? Full of crap?

When testing the vsv, does the FSM call for ohm test only or do you test it with a battery and vacuun hose to see if it opens and closes

Both.

 

[tomatopants]

I'm going outside right now to do what you just did. And if it worked, I am going to give you a really big hug.

 

[tomatopants]

K that didn't work. However, I did notice that the side of the modulator(blue cap) that has 2 hose attachments had no flow in either of them so I rolled up some steel wool to see if that would do anything.


One of them flows freely now, and the other has a little bit of flow, not completely though. Is my problem solved?

 

[landtoy80]

<<<I rolled up some steel wool to see if that would do anything.>>>
What did you do with the steel wool?

 

[MoJ]

K that didn't work. However, I did notice that the side of the modulator(blue cap) that has 2 hose attachments had no flow in either of them so I rolled up some steel wool to see if that would do anything.


One of them flows freely now, and the other has a little bit of flow, not completely though. Is my problem solved?

Wait, back up...

- Are you reseting the CEL each time or just expecting it to go off on its own?
- Did you use the steel wool to clean out the two vacuum tubes? By "a little bit of flow do you mean it's still partially clogged with gunk or that you felt air going through it?

If you have clogged hoses I would imagine other parts of your system are clogged as well. You should plan on replacing all the vacuum hoses and probably cleaning the throttle body as well.

Have you already replaced the modulator or removed the cap to see if it's full of carbon?

 

[landtoy80]

On mine port R is free, port P is plugged.
If R is plugged, you need to replace the mod.
I assume mine is working as it should as i have no code 71

 

[Rocketman]

I chased a code 71 error in my 1993 (165,000 miles) off and on for about a year. I'd clean the temperature sensor and reset the ECU but it would be back in a few weeks. Replaced the temperature sensor and had similar results. Sometimes the check engine light went off on it's own. Other times I just got tired of looking at it and reset it. EGR system checks following the factory service manual were all fine everytime.

Finally bit the bullet and pulled the TB and the upper plenum. Replaced the EGR VSV. Cleaned everything really good. The EGR passages had a lot of gunk in them. EGR valve looked good and operated fine, same with the EGR modulator. Also replaced all of the vacuum hoses on the engine. Some were a little loose.

Reset the throttle position sensor at the same time. That fixed my low idle problem too.

Put it all back together and it's been 3 months with no code 71. Easily passed smog test as well. I'm not sure what finally fixed it but ... So far so good.

 

[tomatopants]

Wait, back up...

- Are you reseting the CEL each time or just expecting it to go off on its own?
- Did you use the steel wool to clean out the two vacuum tubes? By "a little bit of flow do you mean it's still partially clogged with gunk or that you felt air going through it?

If you have clogged hoses I would imagine other parts of your system are clogged as well. You should plan on replacing all the vacuum hoses and probably cleaning the throttle body as well.

Have you already replaced the modulator or removed the cap to see if it's full of carbon?

I reset the CEL every once in a while after pulling the code because the orange light bugs me while I drive.
I rolled up the steel wool into about a 3 inch long strand and stuffed it inside each tube, when I first started, I could blow air into the side with the single tube, but not the other 2, and when I cleaned out the other 2, one of them opened right up, and the other one opened up but is still a little clogged with whatever.

And I checked under the cap, and it's got the slightest hint of gray.

I took off all the hoses and made sure they weren't clogged.


I'm probably going to replace the modulator anyways.

 

[AirMax10]

I am currently getting this code on my 94. Am I going to do any damage to my vehicle if I cannot address it until this weekend? Thanks,

 

[Kernal]

EGR insufficient? Many people have completely removed the EGR system others have driven years with the code.

 

[MoJ]

I am currently getting this code on my 94. Am I going to do any damage to my vehicle if I cannot address it until this weekend? Thanks,

No issue at all

 

[AirMax10]

No issue at all

Awesome! Thank you

 

[MoJ]

Awesome! Thank you

And on my formerly owned ‘94 it ended up being the EGR VSV that was the problem. There’s a simple resistance test in the FSM for it