Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minutes

[ajwgator]

Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minutes

I have a Kohler Command Pro 28 w/Bosch EFI, Spec No. PS-CV745-0004, S/N 3300602011 on a Gravely Promaster 260Z frame. It runs and cuts great for 30-45 minutes and then I get an MIL light. It goes back off after a minute or two then returns to stay on. Continued use results in the engine bogging down and will die if under a load. Reading the flash codes from ECU I get a 34 and 31 (in that order). If I let the unit sit for an hour or so it starts back up fine and operates normally with no MIL light for another 30 minutes or so. The Bosch ECU numbers are P/N 24 584 29, S/N 5000696 and is a 32 pin MSE 1.1 version.

I used the troubleshooting guides in the maintenance manual and realize these code have to do with the TPS sensor and Oxygen Sensor. They both check out OK. When the engine is acting up as described above I can see that the throttle is being held wide open by the governor. I have read a couple of posts concerning similar issues but didn't find anyone that came back to report a good fix for them. When I checked the readings on the TPS sensor I get 945 ohms when full closed and as I rotate the throttle towards full open the reading increases till I get to 1996 ohms but the throttle is not at WOT yet and continuing on towards WOT the reading goes to open (no continuity). Thought that wasn't right so I purchased a new TPS sensor from Kohler. In checking out the new TPS sensor (I haven't installed it) I find that the readings are exactly the same as original TPS above (that is still installed) so I don't think the installed one is causing the problem even though the 34 code is being reported.

Concerning the Oxygen sensor, I removed and reinstalled it after cleaning the tip (it wasn't carbonned up and fins were open) and it is putting out the correct voltages when it reaches operating temperature. So again I don't feel that is causing the problem even though the 31 code is being reported.

I haven't done a TPS Initialization Procedure on the system because of the way the unit starts back up and operates for another 30 minutes or so after sitting. I would think that if ECU has lost the learned setting from the installed TPS sensor it would not start back up and operate fine like it does.

I appreciate anyone's input on this issue because the Kohler dealer in my area say they don't know much about the Bosch EFI systems since Kohler stopped using them 3-4 years ago. Of course they want me to switch it to the Delphi EFI...

Thanks.... in advance....

 

[ILENGINE]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

Find the system ground lead for your engine. Check to see if it is connected to the cylinder baffle, a black phospor starter bolt, or has a stainless steel eyelet. If any of this exist you will need terminal upgrade kit. 24 452 01-s Assuming you have the plastic ECU box.

the code 34 has been linked to a faulty ground, but normally also shows code 21. From my understanding it requires cutting off the old terminal and soldering the new terminal eyelet in its place. Cannot just be scotchlok into the wiring harness.

 

[ajwgator]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

Thanks for the reply & info ILEngine. I'll check that this morning and will definitely report back my findings for everyone's sake. Concerning the kit number you listed, I have a good assortment of solid copper lugs from my Air Force days that I can crimp & solder on. Is there anything else in that kit that would make it better for me to get the kit? Thanks again.

 

[motoman]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

A common theme in auto EFI t-shooting is that wiring is always suspect. Since you have looked at the devices and will look at the ground I would look at the wiring for a possible intermittent short or open (chafed wire touching ground , corroded contacts inside any snap connectors relays, or broken wiring at strain points such as crimps at connectors. The EFI much more sensitive to voltages than non EFI. Since these codes are set after repeated events you may have to use a meter on wire runs (ohms) rather than try to detect while running. Warm up the engine if possible. These are always tricky problems. I'm not sure cleaning the oxy sensor is a good idea. IMO

 

[ajwgator]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

Thanks for the reply and info motorman. I'll be spending some more time on it tomorrow & will definitely use your input. And to ILEngine, my ECU box is plastic. I did make a bit of progress today but I'm not out of the woods yet.

So here is my report after todays troubleshooting and findings. My battery ground lead is connected to a large lug that is bolted to the block about midway up crankcase (not far from the starter). The system ground is connected to that same lug. The bolt is steel and the eyelets are not stainless steel. I took it apart and cleaned the eyelets up with a wire brush and soldered the them. Ohm meter shows good continuity between pin 19 (on 32 pin ECU plug) and grounding lug connection. It was reading good continuity before too but wanted to make sure there wasn't any corrosion under the bolt & eyelets. The service manual wiring diagram shows two ground wires (pin 19 and pin 21) and has a note that states "Two separate 18 AWG wires" but my 32 pin ECU plug does not have a connector in hole for pin 21. Not sure if this could be an issue or not.

My starter bolts are not the black phosphorus bolts. They are definitely steel and one does have a ground on it. It is the chassis ground from the engine block to the mower frame. It does not go into the ECU wiring harness. I also took this ground apart and wire brushed it, soldered the eyelet connection, and made sure there wasn't any corrosion where it connects.

The only other ground on the engine crankcase is on the rectifier-regulator for the alternator. Took it apart and cleaned up like the others and ohm meter shows good continuity from the rectifier-regulator aluminum case to all grounding lug connections and chassis.

The only questionable ground I really found was the muffler itself. The O2 sensor (single wire sensor) is suppose to ground through the muffler according to Grounding note B on the wiring diagram. I could get it to read continuity but I had to really scrape the meter lead pretty hard against the O2 sensor case. The note in the wiring diagram for the O2 sensor goes on to say that "If a slip joint is used, a grounding strap is required". So I went ahead and added a grounding strap around the O2 sensor case with a ground wire and attached it to the same chassis ground connection at the starter bolt.

Got it all back together and took it out for a test run. Good news first, I no longer get a MIL code 34. Bad news is after running for 30 minutes I still am getting a MIL light and the performance goes to crap. The only code that I am getting is 31. I shut it off and let it sit for only 5 minutes and then started it back up. It ran fine again for another (exactly) 30 minutes and same result, MIL code 31.

The service manual has two lines for a 31 code on the "32 pin ECU" system. I don't have a "OBD2" P code reader but one 31 code is for P0174, system too lean; the other is P0321 O2 Sensor Circuit, Shorted to Battery. Each has a note, P0174 has a note 6 which reads "System too Lean used to be O2 Sensor-Shorted to Ground (P0131). P0321 has a note 3 which reads "O2 Sensor Short to Battery diagnostic detection is disabled with SAS fuel-cutoff calibrated out." I have no idea what SAS fuel-cutoff is or if it is calibrated out or not. Anyone have any insight on that?

Well like I said in the beginning of the post (sorry it is so long) I'm not out of the woods yet. Maybe cleaning the O2 sensor wasn't a good idea like motorman said but it was too late by that time. I still think it may be OK but I don't know for sure. I guess tomorrow I will go ahead and bite the bullet and disconnect all the loads and belts off the engine and do a TPS Initialization Procedure on it. Code 31 does say Fuel Mixture or Oxygen Sensor, and System too lean along with Oxygen sensor not sending expected voltage to ECU. I'll do this along with checking the relay connections and look the wiring over a bit more.

Still open to any and all suggestions from you guys too. My brain is about tapped out right now.

 

[ILENGINE]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

You don't say how many hours are on your mower. But Kohler says that the O2 sensor may start to fail above 700 hours. So you could have a sensor issue or possibly the fuel pump isn't working properly after it gets hot causing low fuel pressure, leading to the lean run code 31.

Some of the problems on these engines just can't be determined very easily without the laptop software.

 

[motoman]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

gator, I found Kohler site with their diagnostic software for sale $95. It looks very good at this price. I did not see what platform it uses, maybe a laptop . If your time is worth anything this might be a good way to go. Also a 4 part series on youtube shows how it works.

 

[ILENGINE]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

There is only one problem with the $95 software sale. It doesn't come with the interface cable which is an additional $245.

 

[motoman]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

Mr IL ENG should know, but is this like the HP printer ink which is sole sourced and meant to recover loss on sale of printers? I am not a computer nerd, but interface cables can often be created. Don't know myself. So IL ENG what are the connectors on each end of the cable, if you know. And although costly what is the average shop cost for a couple hours and some parts? Maybe it still makes sense? And IL ENG, you don't run this SW?

 

[ajwgator]

Re: Kohler Command Pro 28 w/Bosch EFI Throwing 34 & 31 Code after runniig 30-45 minut

You don't say how many hours are on your mower. But Kohler says that the O2 sensor may start to fail above 700 hours. So you could have a sensor issue or possibly the fuel pump isn't working properly after it gets hot causing low fuel pressure, leading to the lean run code 31.

Some of the problems on these engines just can't be determined very easily without the laptop software.

gator, I found Kohler site with their diagnostic software for sale $95. It looks very good at this price. I did not see what platform it uses, maybe a laptop . If your time is worth anything this might be a good way to go. Also a 4 part series on youtube shows how it works.

Well I didn't get to do the TPS Initialization Procedure today as a higher priority got put ahead of the list. I did read the replies before I left this morning and have been giving a lot of thought while working today. ILEngine, your statement about the possibility of the fuel pump not working properly is something that I really never considered since it has always started back up fine. The more I think about it the more sense it makes. I always hear it run when I turn the key and also hear the fuel pressure regular dumping the excess fuel pressure back into the fuel tank so I had pretty much ruled that out. After you bringing it up I did a lot of thinking. It is running continuously whenever the engine is running and maybe after 30 minutes it is overheating, slows down and can't deliver enough fuel to meet the demand, the ECU tries it best to correct the situation but can't and turns the MIL. When the engine finally quits or is shut off, the fuel in the lines would cool the pump back down pretty fast. I start it back up and things seem fine again but after another 30 minutes it starts acting up all over again. It would easy to check out by just putting a tee in the fuel line after it leaves the regulator and before it get to the injectors and hooking a gage to it. I could monitor the pressure and see what is going on when it start acting up.

Concerning the age/hours of the mower, the mower has some age on it but I can't find the exact year it is. Its a Gravely Promaster 260Z, Model 992048, s/n 000161. I picked it up used and previous owner had replaced the engine a couple of years ago with the same that came on it. The engine has 200 hours on it. The specs on it are in my first post that started this thread. I can't seem to find a place to interpret the numbers into what exact year they were manufactured. I think that the muffler & the O2 sensor came off of the original engine unless Kohler supplies new ones with a power plant change out. I just don't know for sure but as I posted in the beginning the O2 sensor is checking out when I check the voltage readings it puts out after I get it to temperature. I'm just not able to check it while it is running. I know it is not shorted to ground or battery and is only just reporting what it is reading and it doesn't match what the ECU wants to see from a properly running engine. So the ECU tries to correct it with timing or fuel volume. If the fuel pump is acting up and doesn't deliver enough fuel to meet the demand, well there you go... bogs down, loss of power, popping noise in the air cleaner, all the results the efforts that the ECU is trying to correct what it sees wrong from the data being sent to it. JMO but O2 sensors are nothing but a chemical battery that produces a small voltage reading. Nothing in them to fail mechanically but if can be shorted out or an open but that is usually because of mishandling and not from just sitting there in the exhaust system.

Motoman, I didn't find the $95 software. Was that from Kohler or from somewhere else? I have seen the 4 part youtube before and if that is the same software you are referring to, its not worth it to me because there is way too much "other stuff" in it that really isn't needed IMO. I'm not in business here, don't need to keep up customer info, maintenance history, engine numbers, ect... All one really needs is an OBD2 code reader for the P codes and that it. You know like we have for cars today. Of course ILEngine's info about the software not having the interface cable is pretty good info too. I don't think you should jump on him like you did. He isn't trying to "run this SW" like you said (whatever that means). The way I see it he is only sharing information and passing on knowledge to anyone who asks. I for one appreciate any and all input to problems I'm having and trying to find answers. Its great to be able to do this and I think it is "priceless" information one can't buy anywhere.

Well I gone on too long again. I will report back after my next maintenance session. Again any input is always welcome and I really do appreciate it!