Cat 140H. Dealer did a service about a year ago. Machine has been playing up ever since. Briefly puts on the alarm under moderate engine load and logs a sensor supply voltage code. Any guesses?
to my inexperienced mind the atmospheric pressure of 103 doesn't sound right?
Negative oil pressure?? No pressure means zero pressure.
Odd set of figures, is that with the engine running or off?
I looked at the picture before I read it and sensor supply came to my mind as well. -2 oil pressure does not bother me. But why is engine speed and oil pressure 0 when there is so much boost pressure showing?
Boost sensor unplugged or damaged? Birken found the red flag
It appears there are 2 different boost pressure sensors misreading, one is turbo outlet and the other might be the intake manifold, somebody with more specific info will have to comment.
It would be nice to know what the Code was............ It's a calculation. EOP sensor reads absolute pressure. the ECM takes that reading and subtracts the atmos press reading, then displays the result. The -2 is nothing more than a slight difference in two sensors. There are two pressure sensors in the inlet manifold. One reads absolute pressure, the other reads boost pressure (absolute minus atmospheric). Line 5 - 413 kPa. Line 6 - 413 minus atmos pressure 103 from Line 2 = 310 kPa which is near enough to the displayed 308 kPa to make no difference. But as Birken pointed out the engine is not running. See line 1 - 0 RPM. So why does it allegedly have 310 kPa (approx 45psi) of boost pressure in the intake manifold.? It wouldn't ever see that even at full power on a dyno. Wiring fault in the turbo boost sensors or in the branch of the engine harness that connects to them.? Harness rubbing against something and worn partially through.? Dealer tech trapped/squashed/cut something electrical when performing the service.? EDIT: Sorry there is only one pressure sensor on the inlet manifold (the other one is temperature). It works exactly the same as the oil pressure sensor, displaying an absolute pressure value. The boost pressure value is calculated by subtracting atmospheric pressure from the sensor reading.
Those dam mice!!
But in this case I’m betting the mice had 2 legs not 4.....
I'll have my own guess the problem in the dozer section this evening.
All good observations. As expected, Nige is straight onto it with his treatise regarding the relationship between atmospheric pressure and absolute pressure. So the story is, the guy doing the PM service stood on the manifold pressure sensor and broke it. He replaced it with one that fitted nicely but for reasons that still remain unclear, the wrong part number. This led to three field service calls and another two new sensors. The trouble was that the new sensors were ordered by using the part number from the "old" sensor and not looking it up in SIS. The next stage was going to be a new engine harness but the customer asked yours truly for a second opinion before forking out the cash. The moral of the story is that computers aren't always going to tell you what's wrong with a fault code. Always look for sensors that are giving, as far as the ECM is concerned, a plausible reading, but an implausible reading IRL.
And FFS before replacing it always check the Part Number of the sensor with the Parts Manual or in SIS before ordering another one................
Nice! Now I need you Cat gurus to answer mine in the dozer forum. I puttingbit there shortly.
That's better.........
Been thinking. How in the creation of Christ did he manage to stand on that sensor.? You'd need the hood off and why would you do that for a service unless you were doing something else at the same time.? I still can't see the need to be stood that high up unless you were replacing a lamp in one of the lights on the cab roof. There ought to be more to this story.......... I buy that it got broke, I don't buy the how.
2000 hr service. Hood off for a valve set.
OK, I get that. According to what I know he shouldn't have been on top of the engine without a safety harness. Was he trying to cross from one side of the machine to the other for some reason.?
I dunno. Expect the unexpected I suppose?
Fred Gassit said it best - "You fuggin' caaaaaahnt..........!!"
Only an idiot doesn’t check for any active codes or faults after service but hiring idiots is in vogue these days.
If I read CMark's OP correctly there were no Active Codes, only a fleeting one that came & went at random and only appeared after the machine was back working. "Briefly puts on the alarm under moderate engine load and logs a sensor supply voltage code." TBH the clown who did the "fix" with the sensor from his toolbox that just happened to fit the hole in the inlet manifold should've had it rammed up his ringpiece - sideways, and without the benefit of any lubricant............
it was late last night and I missed that tidbit in the initial post…I was thinking it was throwing a code and he shipped it anyway (seen it a thousand times where nobody cares enough to do what they ought to)
I can’t imagine replacing the sensor and not doing a status check on the reading. That would have caught it right away. I also had to chuckle when Nige said wear a safety harness while doing a valve set on a 140h. Oh what a different world we live in!
No that's not what I said/meant. Sorry if I didn't explain it clearly. CMark said - "So the story is, the guy doing the PM service stood on the manifold pressure sensor and broke it." The only way I could think of for a mechanic to be able to stand on that sensor, accepting that the hood was off for performing the valve set, is that he must have been up on top of the engine for some reason. Why.? The only way I could see that happening is if he wanted to cross from one side of the engine to the other without first climbing down to the ground and then back up the other side. Knowing what Australia, and especially their mining side, is like regarding H&S to be climbing at that height above ground (not standing on the tandem doing the valve set) would supposedly require the wearing of a safety harness although I completely get that there would be nowhere to attach it to unless they had one of those "goalpost-type" anchors positioned next to the machine. I have no idea of how CMark's customer is on that front but if a safety germ spotted the mechanic climbing like that over the top of an engine in a lot of places I've been there would have been all sorts of questions asked.