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Thread: Use of Memory Clear and Diag Check for ECU Errors instead of MUT/OBD

  1. #41
    Join Date
    Aug 2009
    Location
    Brisbane, Qld, Australia
    Posts
    624
    thanks,

    I'm still making it up as I go along .....

    definitely difficult with "error but no error code".

    By way of explanation (your question about crank sensor) ... the way the fuel system works .... inputs are accelerator pedal position, engine speed, engine coolant temperature, idle speed adjustment and boost pressure. The control rack is moved based on data within the ECU (its map). The control rack actuator moves the control rack until the control rack position sensor says its in the right position. If the sensor fails there is a sub-control rack position sensor used instead.

    The rack position sensors, actuator, and engine speed sensor are all in the fuel rack on the side of the engine.

    A little bit more complicated as there is "pre-stroke" for timing and the above for rate. But all part of the the same "sub-system" within the ECU.

    If both fuel rack sensors fail then fuel is delivered based on engine speed only ... limited to 1800rpm in my engine.

    As far as I can tell the crank sensor is not involved in fuelling.

    The consistency of 2,000 rpm you describe has to be a clue. Is it a "hard" or "soft" stop. ie when stationery, out of gear, foot on accelerator, does it rise quickly then suddenly stop rising always at the same revs or does it slowly approach the limit? Is it the same under load and not?

    Something crisp and very consistent tends to be digital, ECU related, though may be mechanical. Something "soggy" tends to be fluid flow (air, fuel, exhaust) or mechanical (worn) related.

    At the moment I'm tending to home in on the fuel rack as that and the turbo boost pressure are the only parts that create errors that lead to back up mode. Without discounting anything else.

    Useful test would be to disconnect wiring to the fuel rack. See how the ECU reacts to not having rack position sensors, actuator, and engine speed sensor. Depends on engine. The engine will not start - don't even try - but we should see error codes. If we are lucky its something silly like a bad electrical connection in that area.

    Definitely a challenge trying to find a problem that the ECU sees but doesn't tell us about. - that's a software bug. But there's also a real problem.

    Also. If you have a voltmeter measure battery voltage with engine stopped (around 12.7v) and engine running (around 14v). Just picking up on the clue of battery replacement and the "won't start" morning. Do you do much driving at night?

    Sorry, still more questions than answers.

  2. #42
    Your thoughts and your process is all helpful! It may just solve it which would be great!!

    Right so if it is the one of them other sensors in the fuel rack, that cant be tested individually, and it would be a large replacement part of all the fuel pump assembly mounted below the rail, (couldnt post a link so private messaged you the part I think we mean) or am I looking in the wrong place?

    With regards to the fault, the truck will drive and run smoothly upto 2000RPM and then just feel like it hits a rev limiter, when it started doing it while driving I could be cruising at 70MPH, and if the fault happened it would literally drop the revs and speed to 2000RPM, and slow the truck down straight away. Once I was overtaking with acceleration and it kicked in and I thought my head was going to go through the windscreen with the jolt from it dropping the revs back down. When in limp mode it is a noisy engine, as if something has changed or opened to put it in this limp mode for safety.

    Its Saturday here in the UK so am going to have a look at the truck today as not working, and I will disconnect that fuel pump (as think this is where you are saying those sensors are inside - whats in the link above) and see if a fault code is given, if I'm looking at the wrong part where these sensors you mention are inside please let me know. I will take battery voltage readings too, trying plugging the vacuum boost pipe I mentioned hopefully to bypass the sensor, I've also found in the workshop manual how to test the throttle pedal so as this was in the trouble shooting table will test this how it describes with voltmeter to see if anything obvious is there.

    I dont us the truck at night, very little use during the day to be honest, maybe a couple of times a week. No problem with all the questions, appreciate your help and knowledge.

  3. #43
    Join Date
    Aug 2009
    Location
    Brisbane, Qld, Australia
    Posts
    624
    all useful info, sounds like a very "hard" condition. Suggests the ECU or something mechanical is "switching". Just the ECU not telling us what it thinks the fault is.

    I think we can discount the exhaust retarder (for now) as that would be much "softer".

    the link you sent me to the fuel pump looks right. Looks like one connector for lots of things inside. Really we are still probing to see if we can change or detect something.

    a sort of methodical "change something, see what happens to ECU and engine operation".

    The voltage check is just in case. The engine will run quite happily without alternator charging for quite a long time.

    I believe its too early to think about replacing parts but sometimes there's little option - but the trick would be to pick which part!

    When you disconnect the wires from fuel pump have a look to see how clean the pins in plug and socket are.

  4. #44
    Join Date
    Dec 2010
    Location
    Greeley CO
    Posts
    979
    Don't limit yourself to MF dealers. Around here there a lot of diesel repair shops that know a lot more than the dealership about these motors
    1992 FG, 1994 Hallmark camper.
    1961 CJ3b, V6,OD,PTO winch etc.
    1969 Jeep Commando.
    1998 Harley.
    2, 1982 XT 550's
    1953 Buick Special, that I get out about once a year, 62K original miles.

  5. #45
    Ok good stuff, I'm not looking at replacing the pump just yet, completely agree would rather find the problem for sure first!! I have disconnected the pump and was getting fault code 26 and 11 when that was disconnected, which are Governor Servo, but I dont have a fault code 26 in my list of codes, but either way it is picking up a fault which isnt there when it is connected, so wondering if this may be not the one.

    As for voltage check am getting 12.4 volts on idle and 13.85 when running.

    Just started looking at the accelerator position assembly, and what I have on section 13-54 of the manual is a complete;y different loom and pedal assembly from what I can see, so come back inside and on computer to due and look through the manual again!

  6. #46
    Join Date
    Aug 2009
    Location
    Brisbane, Qld, Australia
    Posts
    624
    bending my brain a bit

    volts are acceptable. A bit low at idle. Charging ok. Must be a warmish day in UK or battery quite a bit discharged. I'm picking the latter.

    I believe governor servo is another name for the fuel rack actuator. Error 11 is one that would be expected. I also don't have an error 26 in my manual - I'll keep looking.

    We are a little ahead. I believe "11" occurs when there is a difference between target actuator position and actual position. Which means its probably not a sticking actuator, means that the control loop detecting actuator position and moving it to a desired position is not causing an error "11" when all connected. Possibly means the "limp mode" is a deliberate action from the ECU and the fuel rack is doing what its supposed to. Finding nothing is sometimes good. Just frustrating.

    Keeps pointing us back at something in the ECU programme, wiring or sensors, rather than something mechanical.

    I guess I expected more codes. Have you read the past codes? Is there more than one connector to the fuel rack/pump? It also may be that it gives us the worst code.

    Has system gone back to "normal" (error but no error) after reconnecting fuel rack? Always methodically go back to known condition and check.

    As-built not matching manual is story of my life. The accelerator "should" have two sensors. Simple variable resistance. Connected through the same plug. Worth disconnecting to see what code is created. There is a separate code for each sensor. 16 and 24. Strangely (to me) the vehicle is still drivable, sets max accelerator angle to 30 degrees.

    At present we are disconnecting, looking for error codes, then connecting. Generally homed in on the area of fuel delivery. There's really only two things that can go wrong with a diesel. Air and fuel. The engine is controlled by controlling the fuel. We have got as far as "the fuel rack is probably working ok". Again, keeping an open mind, discount nothing.

    If we continue to find nothing we will probably have to start checking sensors. There's a part of this section of the manual that has values for resistance between pins for each sensor and other checks. Is your voltmeter a multimeter (for resistance). We may not find anything but we will know what isn't wrong. Beyond that there's continuity of wiring between sensors and ECU (dirty connections) then the ECU itself.

    If its easy a quick visual look at the ECU. Just looking for obvious things like dirt/dust/water damage, etc.

    Probably a long shot. Is there a Mitsubishi shop near that would lend you an MUT (Multi Use Tester). As well as diagnostic codes it can tell us the values the ECU is reading.

  7. #47
    So thought it would be worth putting an update up incase others come across this in a search to solve their problem . . . . .
    Right thanks to Mog, who sent me a workshop manual, and Gait (who has helped lots behind the scenes with his knowledge and time), my truck is fixed and working better then ever and can confirm I got my code reading sorted.

    It was giving a code 23 in blink code history, (which is not covered or listed in the manual I had) but when in limp mode was giving no blink code or indication what was wrong, by accident I found that it would give code 23 (by normal blink code reading - lead unplugged for diagnostics) after 15 seconds if the engine was running - this is also the point when the limp mode would kick in, so the truck/ecu would only see and find the fault if the truck was running as when then switched off it would reset and be fine, and in normal diagnostic reading would read no fault present.

    The outcome I believe for blink code 23 was a TCV (Timing control valve) in the diesel pump - this on mine a VP44 Bosch pump which is not an unscrew-able part form the pump itself (but think it can be done on some bigger Canter pumps looking at some manuals for the trucks) but on my little VP44 after removal and getting it on a test rig it required the pump to be reconditioned and new EDU on the pump itself. So not 100% sure if on my truck blink code 23 is the TCV or a generic fuel pump issue as no individual parts to replace when fitted to the truck, but either way this code 23 pointed to the pump or part in it being at fault and this has fixed it.

    Thanks again Steve!

  8. #48
    Join Date
    Aug 2011
    Location
    Gladstone QLD. Australia
    Posts
    550
    Thanks for putting up the follow up on your problem. It is not that it will ever be a problem with my Canter but will certainly be of value to some of the others with latter model trucks.

    Dan.

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