S27 F08 Error Code - Confused

[RSR]

I need some help ...

Back in May, I had an S27 F08 error code pop up on my tractor. A quick google search led to a discussion on this forum that it was a wiring harness error. I popped the hood, did a cursory check to see if there were any wires/harnesses loose, found nothing. Shut the hood, and the error went away.

Fast forward 3 months, and the error is back. It flashes the error, along with the red exclamation point blinking every second.
up the underside of the hood to the headlights. The chafe tape had gotten pushed back, and it had rubbed against a hydraulic line. The insulation on the red and black wires was rubbed off (zoom in on the attached picture).

All I could do to fix it (there is not enough cable to cut and reattach the connector), was to get a couple of wraps of electrical tape around the wires.

This is where this story gets interesting/confusing.

Convinced I had found the problem, I turned the tractor back on, and the error codes came back on after the usual 30 seconds or so.

At this point, I thought, "maybe the error codes just need cleared". I have no idea if this is true and that error codes must be cleared. I had also read that on some tractors you can clear error codes by cycling the key on/off a couple of times quickly. Again, I have no idea if that is true or not. But, I did it, and the error codes went away, and I couldn't get them to show back up.

[Side note - when I first started the tractor, the headlights were on, and the bad wires were leading to the head lights. So, I convinced myself that was probably the culprit, and may explain why the error code came on in May, and then went away. That is, I may have bumped the lights on in May, which triggered the error due to the bad wires. Then, opening and closing the hood jiggled the wires enough that any short due to contact was moved enough to make it go away. Then, the problem slowly got worse, and bumping the lights on caused the error code to reappear.]

Pleased with myself, and my logic for explaining the problem and the fix, I went to bed. When I got into work this morning, I decided to look up in the shop manual during a break to see if there was any additional information. I looked up the error code and found, S27 F08 with a 1 Hz blinking exclamation point is NOT a wiring harness error. It's an "EGR Position Control Fault".

!?!?!?!?!!? (All of my self-congratulatory problem solving and logic just went out the window).

The manual says that the first step in correcting this error is to make sure there is unimpeded airflow to the engine. When I popped open the hood to start investigating last night, I found some mouse turds around the battery. Now I'm wondering if a mouse got up into the air intake/filter area. Despite being garage kept, I've had this happen on a car a year ago too. (I pulled over 1 cup of nuts out of the air filter container on my Honda when doing a routine air filter exchange).

I won't be able to investigate until I get home tonight, but I'd love to better understand how the errors disappeared in the first place by fixing the wires, and cycling the key, and then why they didn't come back on, as it appears that I actually solved a problem I didn't even know existed, and which was different than what the error code indicated.

I'm very confused right now.

ps. After inspecting all of the wiring last night I'm not very impressed with how the wires are connected to most of the harnesses. There is a large length of exposed wire at virtually every connection, with little to no chafe guard or shrink wrap to protect against the elements. I've ordered some chafe tape to correct the one known problem and am considering adding shrink wrap to all of the connections to minimize the chance of dirt/water working into the back side of the connectors. Thoughts?

 

[Avenger]

I think the wires to the headlights were a red herring. I believe it was just coincidence that you found that issue and the issue appeared to be solved. It could be a mouse nest inside your air intake. Consider this: The codes appeared in May, you popped the hood to look for issues, jostling the tractor as you work around the hood and repair the wires. This causes the mouse nest to settle a bit, allowing more air past. Mouse doesn't care for this and rebuilds its home over these last few months since, thus blocking the air even more.


I see that you have a shop manual, that's perfect! Check that air intake well, might as well clean the filter while you're there. But suspect it might also be that ECU wiring harness. My dealer (the dealership mechanic anyway, a few years ago) suspected that might be the cause of an issue I had. He said that he has had to replace the entire wiring harness on these LS XR41 series a few times. But my issue wasn't the harness, it was a small fuel leak that sucked air. ANYWAY, it might be that harness.

-My advise, clean the air intake well.
-Check for mice
-Get an ELM 327 OBD2 reader like this one: https://www.amazon.com/gp/product/B01HXGX8V6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
-Download the Torque app
-Clear the codes that way (I've never head of the key trick, but wouldn't be surprised if that actually cleared codes)
-Run the harness are described in the shop manual.

If that does not work, might be time to call the dealer. They have their laptops that can do magic on these machines.

 

[alexpops]

Ditto on checking the air intake/filter & running the harness(es). Check the MAF sensor while there & it wouldn't hurt to spray it with MAF/carb cleaner. Possible your chafed wires have a short between light circuit/EGR/MAF somewhere else in the harness? Check all your connectors for corrosion/dirt/looseness/sloppy fit. Clean up & seal with dielectric grease as necessary. reading/clearing codes is good up to a point, for more sophisticated diagnostics you'll need a better bi directional scanner & those get pricey, unless you can use on multiple vehicles. The Carnics UVIM comm module shown in the service manual runs $800 on alibaba for just the module or $2800 for the kit. For about $2000, you can get a Launch scanner and their heavy diesel module ($1000 each) which should be usable on other vehicles as well. Then there's the issue of software applicability. My guess is that it'll be cheaper for you to run the harness, check for/fix obvious problems, & if it's not that, let the dealer have at it (those were either 5 or 6 year warranties at the time), so depending on when you bought, you may still be covered if it's not mouse damage.

 

[RSR]

Ditto on checking the air intake/filter & running the harness(es). Check the MAF sensor while there & it wouldn't hurt to spray it with MAF/carb cleaner. Possible your chafed wires have a short between light circuit/EGR/MAF somewhere else in the harness? Check all your connectors for corrosion/dirt/looseness/sloppy fit. Clean up & seal with dielectric grease as necessary. reading/clearing codes is good up to a point, for more sophisticated diagnostics you'll need a better bi directional scanner & those get pricey, unless you can use on multiple vehicles. The Carnics UVIM comm module shown in the service manual runs $800 on alibaba for just the module or $2800 for the kit. For about $2000, you can get a Launch scanner and their heavy diesel module ($1000 each) which should be usable on other vehicles as well. Then there's the issue of software applicability. My guess is that it'll be cheaper for you to run the harness, check for/fix obvious problems, & if it's not that, let the dealer have at it (those were either 5 or 6 year warranties at the time), so depending on when you bought, you may still be covered if it's not mouse damage.

Thanks for the advice. The tractor is only 2.5 years old, so it should still be under warranty provided it's not mice getting to it. The dealer is over an hour away. We wrote into the contract that he would pick/up deliver for warranty issues. But, rather than putting the burden on him (he's a relatively small place) I'd prefer to do what I can first (e.g., clean out the air intake, MAF, etc.). For now, the error codes have also disappeared. So, provided I don't find anything obvious tonight, I'll run it some more and see what happens.

 

[RSR]

I think the wires to the headlights were a red herring. I believe it was just coincidence that you found that issue and the issue appeared to be solved. It could be a mouse nest inside your air intake. Consider this: The codes appeared in May, you popped the hood to look for issues, jostling the tractor as you work around the hood and repair the wires. This causes the mouse nest to settle a bit, allowing more air past. Mouse doesn't care for this and rebuilds its home over these last few months since, thus blocking the air even more.


I see that you have a shop manual, that's perfect! Check that air intake well, might as well clean the filter while you're there. But suspect it might also be that ECU wiring harness. My dealer (the dealership mechanic anyway, a few years ago) suspected that might be the cause of an issue I had. He said that he has had to replace the entire wiring harness on these LS XR41 series a few times. But my issue wasn't the harness, it was a small fuel leak that sucked air. ANYWAY, it might be that harness.

-My advise, clean the air intake well.
-Check for mice
-Get an ELM 327 OBD2 reader like this one: https://www.amazon.com/gp/product/B01HXGX8V6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
-Download the Torque app
-Clear the codes that way (I've never head of the key trick, but wouldn't be surprised if that actually cleared codes)
-Run the harness are described in the shop manual.

If that does not work, might be time to call the dealer. They have their laptops that can do magic on these machines.

Avenger - what do you mean by "Run the harness are described in the shop manual?"

 

[Avenger]

I meant "run the harness as described in the shop manual" as in, look at each wire and connector for shorts.

 

[RSR]

I took a look at the air filter last night. The external filter was fairly packed with dirt on the end closest to the intake opening, but the internal filter looked perfectly clean. I wasn't able to clean the external filter, so I went ahead and ordered a new one, which should get to me by Friday. I cracked open the air intake hose, and visually inspected the AMF sensor. I also inspected the corresponding electrical connections. The lines were clean, the AMF sensor looked fine, and the connections were in good shape. So, the good news is there was no evidence of any mouse damage.

I have some work planned for this weekend, so I'll thrown in the new filter, and see what happens...

 

[RSR]

Just thought I would update this, in case anyone else runs into this error.

I replaced the air filter, and no dice. I then checked all of the wires going from the ECU to the EGR valve (following the trouble-shooting procedure suggested in the shop manual).

This ended up being a pain as the manual showed an intermediate connector between the ECU and the EGR. Well, turns out it doesn't exist on my tractor. Regardless, that returned no problems with shorts, or broken wires.

I called the dealer and he got in touch with the local rep, who mentioned it was likely some carbon in the EGR valve that was causing the intermittent problems. As I had continued to use it, one day it would run the error, the next day it wouldn't, so this seemed to make sense.

The suggestion was to remove the EGR valve and inspect it. I started into that (man is it a pain to get access to things in the engine), but after removing the screws I could not get the valve off. I was worried about breaking something so at that point I cried uncle. The dealer came and picked it up yesterday, planning to replace the EGR valve under warranty.

We'll see what happens next.

 

[RSR]

I thought I'd close the loop on this issue so if anyone else has it, they might know where to look.

After ruling out any wiring shorts the dealer took the tractor back. The regional rep thought is was likely an EGR valve that was getting stuck due to carbon buildup, which was the next thing to check according to the manual.

The dealer replaced the EGR valve under warranty, and that has solved the problem. I've put 10 hours on it since, with no problem.

My dealer mentioned it had quite a bit of carbon buildup inside the valve. He couldn't tell me if that was normal, or not.

I'd still like to know what caused the problem. That is, is there a control issue that is causing the valve to open/close at the wrong time leading to the carbon buildup, or is carbon build up in the valve normal, but there was a mechanical problem that caused the valve to malfunction?

The dealer is supposed to contact the regional rep and get back to me on that.

 

[alexpops]

How high a rpm do you usually run at? Carbon build up in the exhaust tends to come from incomplete burn. Low rpm could be keeping the turbo from spinning up, resulting in too little air for the fuel being injected. How often was regen kicking in? Try running at higher rpms (2k+), even if you need to downshift to slow the speed. The emission crap will be happier.