High exhaust manifold pressure.

[Luckywon]

Hello,
I am not a trained mechanic per se, but I can usually get things going. I’m working on a pc360-10 Komatsu excavator it was a cummins qsl. Stealership replaced the seized EGR in November it ran 20 hours and threw code related to turbo and turbo was rebuilt. Machine went back to work for 80 hour and now code ca2373 high exhaust manifold pressure.
Had operator change sensor it turned light off machine trailer half mile and it came back on. I discover wires frayed and rubbing just before the plug. Repaired no change. Cleaned tube and block no change. The sensor is reading 24.6 psi with engine off. New and old sensor both read the same actually. Testing the wire I get 5v ground and open wire (signal). I don’t have Insite at the moment. Best place to order a good kit?

Does the sensor have a fuse built in? Thinking about getting another new sensor.

Any thoughts are appreciated [/size][/font]

[Nilao]

If you don't have insite how are you reading the PSI of the sensor? BTW that sensor should be reading ambient pressure with the engine off. It should match the barometric sensor reading within a couple of PSI.

There is no fuse for that sensor. Just a power, ground and signal wires.

[Luckywon]

Good morning and thanks for the reply. The backside Komatsu monitor (service side) gives a lot of info. In this case I can see supply voltage and the pressure reading. What I can’t see is signal voltage. I agree I think it should be about 14.7 psi with nothing turning. There are many other parameters I can view if you think of any I should take a look at. I’ve also tried watching these parameters and having a helper wiggle the hardness from sensor to ecm and I did not see the values bounce at all on the monitor.

QOTD: what does it mean when a sensor reads high when its reading the atmospheric pressure? Bad sensor?

I tried attaching picture of the Komatsu monitor. In the pic you can see some of the channels that can be monitored.

[ktblogistics]

had a situation that sensor read higher than baromeric one , tested 3 different sensors with same results, it was damaged wire, isl engine, if you have engine plug pinout and theres easy access to it measure short between wires and sensor plug

[Luckywon]

(03-07-2024 )ktblogistics Wrote:  had a situation that sensor read higher than baromeric one , tested 3 different sensors with same results, it was damaged wire, isl engine, if you have engine plug pinout and theres easy access to it measure short between wires and sensor plug

Hello, that gives me hope thanks. I’ll be away from the machine about 10 days before I can diagnose some more. Will report back.

[Luckywon]

Update: I ran the machine myself the last couple days. When the charge pressure and exhaust pressure sig voltages run matching, the pressures run near matching and all is well. Then suddenly, maybe with a bump…the exh manifold pressure sensor sig voltage goes to 4.7 causing the code 2373. The voltage never changes much from 4.7 even though the pressure reading fluctuates. Eventually it jumps back to about 1.2 volts and light goes off sometimes for a couple hours. So, thinking the sig wire is getting unwanted voltage from another wire but not the supply wire because I checked that it has 5.03.

Was thinking of unplugging at ecm and checking for a pin that has continuity with exhaust manifold pressure signal wire.

[Rawze]

On those Komatsu's, Looking at the the programming for the exhaust pressure sensor ...


== It will set a default feedback value of exactly (170.0 kpa) / 24.6564 psi if there is any kind of fault with the sensor. The screen pic you posted there shows exactly this value, meaning it has resorted to only displaying only its bogus default value. The ecm does this if the actual feedback is out of bounds, and it can read this if the feedback signal is ...

-> shorted to POWER
-> shorted to GROUND
-> if it is unplugged (OPEN CIRCUIT) ... which is also seen as shorted to +Power.

I.E.> With regards to the signal reading itself ... Any of those conditions, and it will read that same default value, so this does not indicate at all that it is getting an external voltage, but rather that the actual signal is currently being ignored.

==========

Fault code 2373 is a little more specific, but not by much...

FC2373 is saying what is wrong with the sensor is that it is shorted to +power, and nothing more. This does not mean that it is actually shorted to +power though. ALL if the engine sensors, if you simply unplug them, the input signal will either go to +power, or -ground. The bulk of them, set for +power... and this is set in the programming, via the 'pull-up-resistor' options for each input pin of the ecm, and to prevent static electricity buildup on the pin, damaging its input.

I.E.> FC2373 is telling you that its either unplugged (open circuit) ... OR... it can actually be shorted to +power (+5 volts). The ECM does not actually know.

so .. we know from the pic you took that ...

>> The sensor has failed, and is only showing its default garbage value.

>> It either open circuit (unplugged, bad wire, etc.) , or shorted to +voltage somewhere. Its 80% more likely to be an open circuit rather than actually shorted to power, but one never knows. It can also be a missing ground connection to the sensor itself, and this makes have full +voltage to the feedback pin too.

some rough guesses..


** Maybe the sensor itself is bad / intermittent. Make sure that you only use certified OEM sensors.. as those chineezium and fleay-bay and Dorman garbage sensors are known to have issues.


** Maybe one of the pins in the plug itself is not making good connection to the sensor, either the ground pin, or the feedback pin.

** Maybe a broken wire for either the ground or the feedback pin between the ecm and he sensor itself.

** Maybe a bent pin on the ECM face connector.

And far less likely.. -> an actual short to +power in the wiring harness of the feedback signal wire itself somewhere ... but far more likely to be a short inside the sensor itself, or an open wire, as any condition of 'open circuit' will cause a fault 2373.


>>> Go unplug the sensor and see what it reads on the screen.

[Luckywon]

Thank you so much for all that. Specifically about reading external voltage in signal wire.
The sensor in the machine now is the first new one although we repaired running wires after replacing that sensor. It’s about 150 from Komatsu I have a brand new one here we plugged in since but never actually screwed it in because it didn’t read any different. But maybe it needed to learn itself a bit?
I haven’t pulled plugs on ecm side yet just to make sure nothing obvious going on there. Dealer said oil can get down in there over time
You mentioned this as well