VIN 1HSHXAHR07J451402 Problem: Key On, POST done.....20 seconds later the fuel gauge (dual tanks) low light comes on and the gauge pegs hard past full. I know it only has about 5 gallons in it. New sending units, from our truck shop, but that's where they gave up. Not too electrically inclined. I measure about 240Ω, so that agrees with empty or nearly so, anyway. Voltage is where it gets a little squirrely. Right tank I get about 10.5 VDC, Left tank I read a quickly changing meh....500mv let's say. Digitals aren't good for rapid fluctuations and I didn't get the Simpson out to see what an analog would read. I know there is a problem.Those voltage reading should be the same, and I think 12VDC. No confirmation on that yet though. Dealer service people simply said: "Can't help ya". Wouldn't even let me look at a schematic, much less print off a section. Or answer any questions. Guess they are busy and don't need my business. I have about 10 Int'l trucks in the yard. That's ok, it's not far to Longview. Went to visit with the local dealer and couldn't get the time of day. So wherever I will be getting any International parts, I know where it WON'T be. Anyway, I could use a schematic of the fuel gauge system if anyone has one... and I am open to troubleshooting tips. I've given it a quick visual but didn't see anything obvious. Even the location of the "System Controller 140041" would be helpful. I did find a piece of a schematic that shows both leads from the tank senders in parallel, one pair to a Zero Volt reference splice, and the other two to separate inputs to that System Controller.
Tony each connector at the fuel gauge has a tan and a grey wire. The grey wires N9A and N9B are ground. With an ohm meter measure the resistance between the both ground wires and a good ground. The ohm reading should be close to zero. If that checks out okay then you will need to rig up a long test lead measure between the left and right side tan wires N36 and N36A. Again the reading should be very close to zero ohms. The signal from the senders goes to the electronic system controller and is then sent on the data link to the instrument panel. Be very careful not to damage or expand any of the connectors. PM me your email and I will send you the diagrams you need. Terry
Thanks Terry, much appreciated. The grey (or gray ) wires...are they actually at chassis ground potential or is there a system ground that sort of floats? I haven't even looked for the controller yet. Hope it's not too buried.
They are chassis ground.
The system controller is under the left kick panel ahead of the driver's door easy to access.
Great! Any problem backprobing the connector, or are we just looking for continuity at this point? I'm sure hoping to find a wiring issue rather than a controller problem.
You are looking for continuity. The 4004 connector at the firewall should be where the harness connects to the system controller. They changed the design I think for the 2007 model year.
This chassis sticker indicates a Aug 2006 build date, so I've been calling it an '06, but I can't find anything as far as a compliance statement for any year. I suppose it could be mfg for '07, but can't say for sure it's official designation. If it doesn't match the diagrams, I'll know.
The system controller butted up against the fire wall and some of the connections were at the outside of the firewall on the early version. The newer version had all the connectors in the cab.
Oddly, the fuel gauge diagram is titled "single tank system" but dual tanks are illustrated. Guess things slip by everywhere. They are parallel anyway, so no matter. Well, as long as I can locate the connectors, I'll be fine. That might help tell which model year it actually is. Otherwise, I'd have to get the office to pull the title. Don't think I need to do that though. Oh and long jumpers are no problem. Got a buddy who builds some really nice ones. Test lead wire, so that are soft and flexible, and heat shrinked strain relief, and either regular alligator clips or micro hooks. He'll make whatever length needed, though he keeps stock on 3 and 6 feet I think it is.
The difference between a dual tank and a single tank gauge system is in the programming of the system controller.
I guess it would have to be, with them in parallel. The standard resistance would be different with them parallel yet on only two inputs. Thanks again Terry. I'll finish this last cup of coffee and go take a look. We had some storms pass through last night and this truck is in a semi-open "building" at the moment. I don't care to crawl around in a puddle, so it may wait if I get the readings I hope to get. Anything BUT the controller itself. Wire I can re-run. Have a great day!
Hmmm. At the controller connector, cavity 26 is not in use. The way I read the diagram it should be J9G/18GY. Been storming and is still dripping so I’m not hurrying. But if it’s ground, it may be they are picking that up elsewhere. Similar deal on controller connector cavities 4 & 5. 4 not in use and 5 is open to tan on L side, >500K right side. Definitely some bad connections scattered about. For test purposes, it appears that these are isolated wires, so what is the consensus on tapping the proper wire directly at the controller and running to just say the LH sender? I can make secure connections on both ends with a little work if there is no risk of damage. I don’t see any, as long as the existing wiring is out of the jumper(s) I build. What say yee?
Can you post a pic of the drivers side of the firewall where the connectors are?
The lighting is poor at best, and with the cloudcover today I had to work by flashlight. (that's a whole different story). I'll bring my inverter tomorrow to run a trouble light and maybe get some decent pics. I have not actually broken down a firewall connector yet, just the chassis/dash connector, with the lever lock. If I do end up needing to get under it, (I know it's coming) I might get an empty bay in the truck shop where I can get it off the ground and at least use a creeper but as it sits, I can't get under it. So you think maybe there is a risk in what I propose?
OK, I'll admit a bit of confusion here. The drawing indicates that the 4004 controller is exterior dash panel left side. Up on message 9 you said on the newer models it was in the cab, behind the drivers kick plate,which it where I found it, the connector is as described, a two row 36 pin 90° clamshell. That's where I've been probing and finding the unused cavities in the female side. There is a large feedthru bulkhead from the engine side to the interior, but in order to route these particular wires, our tan and gray, it would seem to be far from reasonable to run to the center of the cab and go though that connector simply to route back to the kick panel area to hit the controller. Plus I find no tan or grey in that feedthru. It's close to a large power junction also in the engine compartment.
I sent you the diagrams for the 2007 to 2010 just in case there is a mistake in the manual. Can you double check the VIN that you posted? Terry
There's the door pillar sticker. Those other schematics, by memory, don't look remotely like what is there on the truck. The first ones seemed to follow closely. I take it there is some objection to my test proposal? It would seem I need the pinout for the body controller for the newer version as well. That dwg also shows a dual sending unit on the storage tank, and these are identical.
Tony I can send the manuals as a PDF. They are 8 and 10 meg files. Will your email handle them? Terry
Yes, it should. I've sent and received much larger files than those. I don't see problem until I get in the hundreds of meg file size. Then it is my speed more than anything. It times out before they finish.
Got the first manual. On page 96, the fuel gauge that resembles the truck shows controller input 5 in use, which is accurate, with 4 being NC, but still shoes 26 connected, which is NC on the truck. I can only assume that they are picking up gnd elsewhere. Second manual here now. Build dates, if they can be relied upon, rule out the second manual. This truck was built 8-06, that manual starts 3-19-08. I'll look at the gauge circuit anyway and see how they compare. I appreciate it very much Terry!
It would seem that the newer trucks that have the transfer pump have dual senders per tank as well, which makes sense. I have the pigtails on both sides that might go to them, if they were there. If they would reach the current senders, I might think they simply plugged in the wrong connector, but I don't believe they will reach. One of the problem on this truck is that I don't know the history. right now it is a very nice water truck, but I don't know who put the tank on it. Or what it was before. May have been bought as a bare chassis and a 3rd party did the tank. If they did, they did a nice job. But if it was something else and been stripped back to a bare chassis, I have no idea what it was, or was wired for. I can't fit under the truck well enough to find a transfer pump, provided there was one at all and that it was left if/when the modifications took place.
OK, how about this, since there seems to be reluctance to my test. Since connection 5 on the controller is (or seems to be at this point) correct, I can snip it for the moment, and take a resistor somewhere in the halfway range of what the sender should read and run it to ground and see if the gauge runs up to about half a tank. That ought to take about 10 minutes or less. I understand the reluctance, but I realize it's all on me if something gets cooked. I'd never hold it against anyone here if my idea turned sour.
for reference sake
We can rule out that it is a newer model. After 400 pages I find all sorts of devices and circuits that simply aren’t there. Just to start, no DEF and go on from there.
Tony did you do the test I mentioned above? That looks like the early system controller. are there connectors on the front protruding through the firewall?
Yes Terry, I did. The RH grey checked 4.5 Ω to chassis, RH tan ~1.13 to chassis LH grey checked 3.8 Ω to chassis, RH tan was open to chassis Tan to Tan was around 1.5 Meg Ω, indicating a problem, in that they should be tied together at some point. There are feedthrough connectors in the firewall, one of which I believe goes into the back of the controller. Here are a couple of pics of what I see. Last two are the 36 pin connector I believe goes to the controller. The larger feedthru is above it.
Inside the cab, at the kick panel:
Error post 27, line 1 RH tan to chassis ~1.3 K Ω to chassis
Tony measuring from pin 5 on the 4004 connector to each of the tan wires on the fuel level sensors what is the ohm reading?
The harness that connects to the right tank will probably go across the top of the transmission on its way to the chassis harness. A good place to start looking for a problem.
Pin 5 (gray) to L tank (tan) open, R tank (tan) ~500k That's what's throwing me....it should be tan all the way, not grey. But that grey (at the controller is NOT grounded, at least to chassis)
In essence, pin 5 on the controller, even though it is grey despite the drawings, should go through the cab/chassis connector and out of the cab (that feedthrough I can't be certain I have found) and end up tan and split between the two tank sending units. And the grey (at the sending units) stays grey and hit ground at some point. That's why it seems to make sense to put a 150 Ω resistor from pin 5 to ground....to make sure the controller is good. btw, all these tests are done with the batteries d/c and leads shorted to drain any caps in the system
The harness to the right tank should be able to disconnect and cut all the zip ties and undo the clips holding it to the top of the transmission and get the harness out there you can get at it. I bet there is a worn/corroded spot somewhere. Follow the wires where you can and pull on them and see if there is weak spot where pulling on the wire will break it.
Looks like that's where I'm at...and a little aggravated that the truck isn't in the building I took the time to clean up and clean out to work on stuff in. It's a good size building, with lights, air, and electric service. It's been taken over by welders repairing machines. I'm stuck in an off-season firewood processing lean-to that may as well have no roof, has no electric service, etc. Just like the side of the road, but with shade. And water puddles. I'll see if at least I can borrow a jack and stands from the truck shop and get it off the ground enough to get under it. Even without the puddles, the floor is so cracked a creeper doesn't help much. I'm sliding around on cardboard where it's dry enough, but it's tight. And to make things worse, I sat on my only pair of glasses and broke them in two when changing after coming in yesterday. So I'm blind up close, and will have to wear safety glasses just to keep the road grime out of my eyes. It is past time for a new script anyway. Just didn't want to do it today. Enough whining...the truck is broke and I have to fix it, so on with the show! It's funny though, because with my wire sniffer, hooked to the tan on either side, the tone goes just about everywhere. I can't pinpoint it. It's as though one or both of the tans is shorted to something that is common to a lot of circuits. I can't get away from it when probing under the dash. Doesn't help that I'm going deaf and have to run the gain up, but such is life. Maybe I should re-retire.
New findings Harness connector, harness side pin 4 has continuity to the RH harness tan. No ground resistance at all, indicating that between the two tan wires in the harness do not join in the harness (possibly open connection or LH tan harness side is connected inside the controller) Will make same test from LH harness side, hopefully to pin 5 edit to add that grey on harness at RH tank is NOT ground potential. Several Meg to chassis. Should be chassis potential; GND Same test LH side no continuity found on any pin on that connector. I believe there is a wire break in at least the tan wire from the LH harness connector. Grey wire LH connector 35+ Meg to gnd. my temptation is, at this point to provide ground for RH harness and reconnect or sub in a resistor while leaving LH d/c
If you leave one side disconnected the gauge readings will be off or the gauge may not work at all. The system controller is programmed to see 15 ohms empty and 16 ohms full.
Papers I have say 29-37 for full and 234-246 full You have more papers?
The senders are connected in parallel so the resistance will be half.
Yes, I know. Rt = R1*R2/R1+R2 For 2 resistors. 3 or more it’s slightly more involved. Series-parallel resistance networks can cause some head scratching. I’m fairly well acquainted with electronics. What I’m wanting to prove at this point is more that the controller is functioning properly. I’ll take just about any reading except way past full and a low fuel lamp on
The system controller is one of the more reliable components I have seen. I have only ever replaced one. I still suspect a damaged harness.
I'm sure you are right. But now that I've gone through all the multi-pin connectors and deoxidized them, I'll feel better about the rest of the circuits. It still strikes me odd that this truck is such a departure from the diagrams you found. I never saw a single reference to the 36 pin connector on the firewall that evidently is a controller connection. I don't really care, but it just made this a bit more confusing. And apparently the sender wiring does not go through the cab/chassis connector near the doghouse in the cab. I got my continuity with it unplugged. Since these trucks were offered with different engines, it makes me wonder if they had completely different harnesses. Doesn't seem likely but I have no explanation. My plan, if wiring the RH sender works as predicted, is to abandon the existing LH harness and make the RH the master and run a pair over the transmission to the LH tank. But I will still get under there and clip out the abandoned wiring. I'm sure the next guy won't need the confusion. Plus I'll be able to examine the rest of the harness in that area for any obvious damage. But as long as I get a good ground, and provided I can locate that common "zero reference" point, I'll pull those terminals and give them a good cleaning. All based on results of the rewire of the RH side. The owner, when I was complaining about not being able to fit and work under the truck said he'd have one of our fabricators build a couple of drive on ramps. I'm sure he won't have them before I'm done, but the truck shop guys might use them, enev though they have several air/hydraulic jacks and plenty of stands. Knowing this fabricator, they will weigh 1500# and I'll need a forklift to put them in place. I had to explain that if he did that, they couldn't be simple, flat top surfaces. They needed pockets or rails front and back to capture the tires. He hadn't thought about the possibility of a truck just rolling off the top. Then he started talking about 2 and 3 level ramps. I stopped listening then. So much for the week. Now I get to try and catch up around the place. I think I'm the last guy on the road to mow. I like to wait until the clover and paintbrushes bloom and go to seed, but that still leaves a lot to mow. At least it isn't hot yet. Have a great weekend all!
Tony Part of the harness after it goes through the 9700 connector at the left rear of the engine goes to the right side of the cab and then through the firewall and then back across the cab behind the firewall to the left side. The fuel gauge wires may enter the cab on the right side not through the white connectors on the left. I have always wondered the the engineers did that.
I'll admit I haven't really crawled up on the right side of the engine compartment to see if there is another bulkhead, but that's entirely possible. I was just going by the continuity I found on that 36 pin connector on the left side. When I found it, IIRC, the chassis/cab connector was open, so that makes me think that particular connector goes directly into the controller, except from the front, right at the firewall. If they did such a zig-zag move from R to L I would also have to wonder why. I'm sure there was a reason, but it's anyone's guess. Seems a little strange though. Plus it doesn't match the diagram, which clearly shows it going through that cab/chassis connector. Of course, I may be dealing with someone's rigging and this isn't actually correct.
If I remember correctly its not a bulkhead connector its a big rubber grommet.
On the RH side of the engine bay? If I have to replace part of this harness because of lost insulation and wire corrosion then I want to make my connections as close to a safe area as possible. Perhaps just ahead of wherever it penetrates the firewall
If you could access the gauge wire at the rear of the 9700 connector B11 connector probably the simplest. Then use a good ground for the senders. I suspect you have more than one wire in the harness with a problem.
Well I probed that connector, specifically at B11 and did not find continuity, iirc. But if the 36 pin connector does actually go into the controller I can’t see how it would get to 9700. So Monday I’ll plug it back in, based on the assumption that it doesn’t go directly into the controller and see if I can pick it up on B11. That’s where it should be, I agree. If it’s there, I’ll find out if it is making it to 4 or 5 at the controller. If so, then the RH harness is good on the tan and is lacking on the grey (gnd) side only. I did measure 10.5 V to it at one time. If it were a clean wire and all good connectors I would expect closer to 12, but coming from the controller no telling. I agree that there is likely more poor wiring or connectors in play here though so I plan to get under it yet to look.
That should have read 16 ohms full and 120 ohms empty.
I knew, Terry. No sweat. Two resistors of equal value measure 50% of their value when in parallel, and 2x when in series. Basic electronics. I figured you just slipped a decimal or something. Unequal resistors require a bit of calculation, as in the formula I mentioned above. When I work on something with oddball resistors spec'd, or close tolerance, I'll play with combinations to get what I need. I keep a fair collection on hand and since the price isn't really that different in the relatively small inventory I do keep, I nearly always buy 1% precision resistors. One of my hobbies is restoration of antique radios and old ham gear. So I get to play with it sometimes. Not lately though, too much work getting in the way of my fun.
The 36 pin connector to the controller (there are two, actually...on behind the kickplate and one on the firewall). The tan and grey wires I never could find are actually on the engine compartment side. I traced them back to the connectors at the sending units and the RH side was good, very low ohms. The LH, not so good. So, figuring I'm running new wire at least that far anyway, I snipped them and soldered on a 150 ohm resistor to each tan wire and chassis grounded the greys through the resistors. Unfortunately, there is absolutely no change in the behavior of the fuel gauge. The only thing different from the schematic is a tan wire A36A that comes from J36A and goes off to "Telematics GenI Module (2J) CH3_36 that has a note on the schematic that simply says "W/ Aware". That I have not looked for so obviously not tied it to the tan from the senders. Part of what I find confusing is the way they show 3 tanks, 3 senders, but only 5 pins at the controller for the tans. The greys are common of course. The tank specifically labeled for the 8600 has it's tan N36A running through a connector associated with the transfer pump. There it changes to J36A and joins J36B on pin 4 at the controller. So that tan never goes through connector 9700 at all. Might note that the Telematic reference only applies to the two parallel tanks on N36E and N36D until they pass 9700 and change to J36A to pin 5 and J36B on pin 4. So N36A/J36A/N36E/J36B and all the tan wires are common, with only the Telematics leaving that schematic on A36A, assuming that module is used. Looks like a lot of wasted wire to me, and since they are all essentially a loop, I don't see how they get a separate read from the tanks. In any case, with my resistors in place and the greys grounded....I expected some changes due to eliminating anything untoward under the chassis. Unless there is a 3rd tank hidden out somewhere, I'm beginning to question the controller. What am I missing?
The controller processes the signal from the tank senders and transmits it to the instrument panel on the data link. It could be the instrument panel causing the problem. The attached diagram is from the manual for your truck. It does not show three tanks you might be looking at the wrong diagram. I would suspect the instrument panel before the controller.
That may change my testing setup. I had already figured it was the cluster, and the owner was pushing so I bought a used one and it was very clean, likely out of a wreck, and I had to transfer a couple of the gauges from the original to get the full set back that the truck was equipped with, but there was no change in the behavior. It was cheap, and a calculated gamble. Cost less than a single trip to the dealer to scan it, so that's where he wanted to spend the money. Knowing as much as I do know, with the schematics and information you've provided, I probably would not have done that. But it's done. That's one more reason I am beginning to suspect the controller. I have another 8600 in the yard, but it's a 2012, so entirely different setup. If I had an identical model I might be tempted to swap in it's controller just to turn the key on and let the gauges self test and see what happens. Not actually sure I don't, so I might look around. I've eliminated all the wiring between the senders and the 36 pin connector and subbed in known good wire, so this is getting puzzling and looking less like a simple wiring issue to me. We have a Diesel Laptop system, but I never use it and don't know if it would show anything. I figure if it would, the truck guys would have found and fixed it by now. It's been sitting on my list for at least a year. I'll take that schematic and see what changes there are and adjust to suit and see what happens. I'll be back! Quick glance says ground the grey (pin 26) and one lead of a 75 ohm resistor (half a tank for two tanks) and connect the other lead to pin 5. Another thought that may be a clue. When you key on, it POSTS, then everything reads fine. Then a second set of tests apparently happens and the air pressure is analyzed and if recognized as low, the light comes on and the piezo beeper starts....it is at that point that the fuel gauge does it's thing....red light, gauge around to 6:00.
You have pretty much covered all the bases. The controller is programmed for each individual truck. The fuel gauge would be a programmable parameter as the senders for dual or single tanks are the same. I have seen controllers "Forget" part of their programming and something start to not work. In all cases it was a light somewhere on the truck that quit working and started working properly after the controller was reflashed. It might be worth a trip to the dealer to get them to reflash it and see if it solves the problem.
That may be what it comes down to. I'll make my new cable runs permanent and anchored properly so they won't be tempted to start picking my work apart. Then, the way I see it, it only leaves the controller. If a fresh flash won't take, I'm sure they will be willing to sell me a new one. But this truck is only a $75K truck, and I have two machines down right now worth a combined $1.2-1.3mm, so it will just sit until I get the more important work done. Beside, I believe the intent is to sell or maybe rent this truck, but the machines are integral with the operation of one segment of the business that happens to be lagging behind production and these machines really need to be working, not waiting on a water truck. I appreciate all your help Terry, and when I get back to it, I'll come back to this thread and pick it back up.