SteveS Posted September 23, 2009 Share Posted September 23, 2009 Hey guys! I have a 2005 F250, 6.0, 5R110 that is giving me fits. When the engine is first started and the truck is sitting stationary the speedo needle rests at zero as it should. As soon as the truck begins to move, even idling in gear, the needle starts bouncing up and down, sometimes reaching over 60 MPH. If the truck is stopped after that the needle stays up, sometimes steady at about 30 MPH, sometimes still waving up and down. The truck is relatively new to the customer, he is unaware of any tuner software installed in the truck. The truck has 36" tires, the speedometer has not been corrected. The PCM had codes P0500 (VSS A) and P0503 (VSS Sensor Circuit Fault), and the ABS module had U1900 (Communication Bus Fault). The sensor on the rear axle had a small accumulation of metal that didn't seem like it was enough to cause any problems. The customer wanted the diffs serviced anyway, so we looked inside and didn't find any failure in the bearings or the tone wheel. I looked at the fuse panel for the improperly installed fuse condition and all looked OK. There was a harness that was pulled tight across a P/S line support clip, but I couldn't see any bare wires, and no change when I double insulated the wires. We have a chassis dyno, so I was able to test with the wheels turning and still be able to watch the IDS. The ABS module had a good, steady signal, PCM had an erratic signal and the Cluster seemed to have no signal: I ran the truck with an indicated 60 MPH on the dyno (needle varying between 40 and 55 MPH) and time the test. Running at that speed for 6 minutes I checked the odometer on the minute, 4 minutes had 0.8 mile increase on the odometer, 2 had 0.7; seemed pretty consistant and probably about right for the tire size. From those tests I thought that the cluster was the problem, until we replaced it and still have the concern (plus TBC Fault in the display; haven't got that checked yet). I cleaned the ground at the L/F corner of the engine bay that I believe is G105 with no change. So I am looking for some ideas. Thanks in advance! Steve Quote Link to comment Share on other sites More sharing options...
mchan68 Posted September 23, 2009 Share Posted September 23, 2009 Has the diff sensor been replaced? I believe it is updated? Usually U1900 sets along with the DTC for rear speed sensor input (can't remember the number off the top of my head) when this happens. A new sensor has always fixed it for me. Quote Link to comment Share on other sites More sharing options...
SteveS Posted September 23, 2009 Author Share Posted September 23, 2009 Yes, it has been replaced, and the new one is still in place. There has been a few of us work on it along the way, I had to go and ask that tech if the new one was still in there. Although I haven't looked since then to see if the U code is present again. Hmmm... Quote Link to comment Share on other sites More sharing options...
MattB Posted September 24, 2009 Share Posted September 24, 2009 The pids you pulled for the IC are only for output state control, they don't reflect what the vehicle is actually doing. The one on the top flips the needle from 0mph to max MPH, and the other allows incrimental changes. Look at your rear speed signal towards the last 5 seconds of your recording. It looks like crap. You also have inconsistant readings further up on the rear sensor around -12.5 sec and 7 sec., just not as bad. I bet if you zoom in on that it will match the VSS reading to the PCM. Unless you have wheel slip or chatter going on there, the reading should be smooth as glass like the front wheel speed sensors. Backprobe the sensor and monitor A/C voltage output with the O-Scope function on the IDS. If it's inconsistant when it acts up, you have a sensor or ring issue. If it's clean, backprobe at the ABS module. If it's crappy, you have a circuit issue between the sensor and module. Another quick test is to overlay the circuit from the sensor straight to the module. If it's better, it's a circuit issue. If I remember right, these are real common for sensors, fuzz in the connector at the sensor, wires breaking in the rear connector, and chafe along the frame by the fuel tank. 95% were sensors though. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted September 24, 2009 Share Posted September 24, 2009 I understand that TSB 07-11-02 didn't resolve the concern? Quote Link to comment Share on other sites More sharing options...
SteveS Posted September 24, 2009 Author Share Posted September 24, 2009 The pids you pulled for the IC are only for output state control, they don't reflect what the vehicle is actually doing. The one on the top flips the needle from 0mph to max MPH, and the other allows incrimental changes.OK, I should look again at the PIDs that are available in that module. I was sort of thinking that if the only "real" sensor signal ends at the ABS module that whatever I could see in the PIDs would not be what the vehicle is actually doing. I'll look at that again. Originally Posted By: MattB Look at your rear speed signal towards the last 5 seconds of your recording. It looks like crap. You also have inconsistant readings further up on the rear sensor around -12.5 sec and 7 sec., just not as bad. I bet if you zoom in on that it will match the VSS reading to the PCM. Unless you have wheel slip or chatter going on there, the reading should be smooth as glass like the front wheel speed sensors. When I first looked at it I was thinking that it was pretty smooth, but I see what you are saying; it is dependant on the scale I'm using. I wasn't surprised to see that the fronts were completely flat since the front wheels were not turning. Originally Posted By: MattB Backprobe the sensor and monitor A/C voltage output with the O-Scope function on the IDS. If it's inconsistant when it acts up, you have a sensor or ring issue. If it's clean, backprobe at the ABS module. If it's crappy, you have a circuit issue between the sensor and module. Another quick test is to overlay the circuit from the sensor straight to the module. If it's better, it's a circuit issue. It couldn't hurt to look at the sensor signal at both ends of the circuit with a scope. Overlay is also a good idea. Originally Posted By: MattB If I remember right, these are real common for sensors, fuzz in the connector at the sensor, wires breaking in the rear connector, and chafe along the frame by the fuel tank. 95% were sensors though.I can see that I jumped past the sensor and circuits too soon, just because the sensor is new and (I thought) the PID looked OK. Great ideas! Thank you. Quote Link to comment Share on other sites More sharing options...
SteveS Posted September 24, 2009 Author Share Posted September 24, 2009 I understand that TSB 07-11-02 didn't resolve the concern?Well, as I am thinking about it right now I can't remember working all the way to the end of the bulletin. It has been nearly 2 weeks, and I don't have my notes in front of me here at home. Hmmmmm. That is an excellent question to put me back on track; verifying that I completed the TSB will be where I begin anew. Thank you! Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted September 24, 2009 Share Posted September 24, 2009 And if your head isn't spinning enough right now, see THIS TOPIC too. I had a rough one that ended up being loose and dirty power feed at the battery positive cable. I realize this was an older truck but there are some other things to consider if all else fails. Quote Link to comment Share on other sites More sharing options...
SteveS Posted September 24, 2009 Author Share Posted September 24, 2009 I was considering replacing the batteries simply because the rack of new batteries is next to my work area and it is easier to do that than to drag out the scope. Cleaning all the major connections should be one of my steps either before or on the way toward that. I do find it a little disturbing how all the grounds to the bodies these days are an eye tightened against a painted surface. Yeah, I realize that the bolts have the threads that clean the hole as they go in but still... Thanks a bunch, guys, I am re-armed with fresh ammo. I might not get back to the truck until this afternoon the way that my schedule is looking right now. I'll report when I know more. Steve Quote Link to comment Share on other sites More sharing options...
SteveS Posted October 2, 2009 Author Share Posted October 2, 2009 Well, it has been a week, I owe you guys an update. The truck has been left with us as a "no hurry" kind of job. That takes some pressure off at first, but it tends to get put on the back burner and interrupted, too. My schedule last Friday was hectic, but I had a moment when I was expecting a waiting appointment that hadn't checked in yet. I thought I'd get something accomplished on this project, went out to it and it wouldn't crank fast enough to start; "Heerre's my sign". The Costco batteries looked relatively new but I was a little suspicious of them. My waiter showed up, another tech swapped the batteries but didn't drive the truck and I didn't get back to it the rest of the day. Monday morning first thing (the curiosity was killing me) I drove it. Symptom changed so that all was fairly normal to about 20 MPH, then pulsing back and forth between 20-35 till the real speed was 30 something, then steady again. Made sure that all the steps of the TSB were done. Took all the connectors near the ABS module apart, all looked OK, dialectric greased and reassembled. Aparantly I had sunglasses on the first time through, because there on the underhood PDC the lid had 3 holes where something had been screwed to it but was not there any more. So I looked again at the fuses and this time took each out, tested the pins individually, found a couple that were a little fuzzy and cleaned them. The pins on the relays for trailer lights were green/fuzzy, asked for new ones, but don't suspect that this is related. Oh, look: one of the screws that went through the lid also punctured the FICM relay (OK, tiny hole, but still...), nice. No change. We've been having trouble programming with our IDS (like: it won't), just one more thorn in my side, so we had to send it out to get the cluster matched to the truck. Tech apparantly had trouble getting it to configure and had to try a few times. I haven't done a cluster, so I can't comment on what might have gone on there. We get it back and the problem is worse again, although not as bad as originally. Now it will start waving the needle again as soon as the truck starts moving, but now only to about 30 MPH indicated (was flipping up to about 65 before when the truck was actually going about 3). It now still shows speed after the truck comes to a stop again. So I get the idea that we should run a separate circuit between the rear axle and the ABS module. Another tech is assigned to that, and he reports that the needle still goes whacky and now the ABS light is on. (WOW, that really helped me out; Thanks!) So, in any case, I didn't want you to think that I forgot to check in. I just don't have any good news. I am sure that when I get some time to review my notes, review your suggestions and think a little I can find another path. Maybe living in a cardboard box isn't so bad afterall. Looks like I picked the wrong time to quit drinking... Steve Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted October 2, 2009 Share Posted October 2, 2009 You know, this is starting to sound like many of the clusters I have had to replace for erratic speedometer operation. As I recall it affected 2005 model trucks. Speeds would show variations, or would wildly raise to over 100 while cruising local streets. Perhaps there is a way to borrow a cluster? Which brings me to a new topic... Quote Link to comment Share on other sites More sharing options...
SteveS Posted October 3, 2009 Author Share Posted October 3, 2009 I had a little time "to spare" in my Friday and looked at the ABS light issue that we just caused in the truck. C1175 for the rear axle sensor (big surprise since that's what we just touched). Could have been shorted or open, but turns out to be open. The tech used the good 2 wire cable that we usually use for trailer brakes, looks like Romex on the outside, but good, standed wire inside. Open, none the less. OK, the circuit appears to be open. So I purposely unplugged the rear axle sensor, can't be any more open than that, right? Start driving the truck and the needle begins twitching. It waves up & down for almost a block and then it settles in to the speed that I'm actually going (about 25 MPH) and appears to read correctly as I slow to a stop. WTF? Start moving again and the needle starts out twitching for the first half block or so then steady at about the right speed, steady as I come to a stop again. I am guessing that since the ABS creates the speed signal that it can create it from the front wheel sensors, too? There is absolutely no rear axle sensor connection right now. Maybe the erratic needle is not only because of a poor signal, but because the poor signal is in conflict with another signal? Wierd. Quote Link to comment Share on other sites More sharing options...
GregH Posted October 4, 2009 Share Posted October 4, 2009 Well, it looks like the signal starts at the ABS sensors. From there it is hardwired to the ABS module. Since you get wacky performance whether your speed signals originate from the front sensors or the rear sensor, I would guess for now that the speed sensors and associated wiring are not the root cause. The ABS module then makes a VSS signal that is broadcast on a dedicated line. This line goes to the PCM, 4WD, radio and windshield wiper motor. It appears that from your screenshot in your first post, the VSS signal is erratic. Is this from the PCM? If so, than this is merely the interpretation of the VSS signal from the ABS module as understood by the PCM. A couple of suggestions. Access the VSS line from the ABS module. This can be done at any number of places, but I would suggest the radio, since it is inside the vehicle. Measure it with an oscilloscope, and you should see a nice square wave. The frequency is proportional to vehicle speed. If the signal looks crappy, then I would try disconnecting the non-essential modules - windshield wiper motor and 4WD. If the wave gets better, then you may have found the problem. Now, if the wave still looks crappy - backprobe right at the ABS module and compare. Then disconnect the VSS line from the ABS module, and probe the ABS module alone. If you've got a good signal all around, then it may be time to consider the PCM. The PCM takes the VSS signal and converts it to be broadcast on the CAN. The instrument cluster picks it up off the network and does it's thing. It is possible to read the messages on the network, and do it in real time, but not with the tools we've got. However, since the cluster has been replaced, we can guess that the cluster is interpreting the messages on the CAN properly. If there aren't any other issues with network communication while the problem is occuring, then the network integrity is probably ok. That would leave the PCM as a prime suspect... Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted October 4, 2009 Share Posted October 4, 2009 We had several of those as well.... IIRC, the TSB was in response to these ones.... What we mostly saw was trucks doing 30km/h or so while they were sitting still... not so much erratic as just plain wrong... Quote Link to comment Share on other sites More sharing options...
joshbuys Posted October 4, 2009 Share Posted October 4, 2009 If I recall correctly, that TSB is regarding the delamination of the gauge and interferring with the needle causing it to stick....not necessarily be erratic. Quote Link to comment Share on other sites More sharing options...
SteveS Posted October 9, 2009 Author Share Posted October 9, 2009 WOW! I think I have finially won on this truck! I started out with the wiring diagram for the cluster early in the job. As you guys know, there is no VSS signal circuit to the cluster, it comes over the CAN. Soooo.... I made the assumption that the signal came from the ABS Module since it is also on the CAN. Didn't even think about there being a separate VSS circuit, because it is broadcast over the CAN, right? So then when I read Greg's post I had to wonder what the heck he was talking about with the VSS signal circuit, until I looked at the diagrams for the other modules. Ahhhhh..... Armed with a fresh perspective (after putting it off as long as I could) I went out to the truck. Opened the door and looked right at an aftermarket stereo unit; crap! Pulled the dash panel off to get it out, looked underneath it and saw some wires that were not connected. Once it was out I could clearly see that there was a group of unused wires in the adapter harness with male bullet connectors, and they were all clustered together. The pink wire on the aftermarket harness adapter connected to the Gray/Black VSS circuit. So the bullet terminals were probably rattling against each other randomly, applying who knows what to the VSS circuit (ground? power? noise?). When I first looked at it they were bundled together. This is after I separated them to have a closer look: Insulated all the terminals, went for a quick spin and the speedometer looks normal. Put it all back together, went for a longer drive and it (so far) is fixed. Thanks, everyone for the great ideas. Greg, WOW man, I can't thank you enough for opening my eyes about this system. I would never have found it with my flawed understanding of the communication path. Thanks again! Steve Quote Link to comment Share on other sites More sharing options...
GregH Posted October 9, 2009 Share Posted October 9, 2009 Glad to be of service. You guys have screwed my head on straight more times than I can count, so it is nice to return the favor... Quote Link to comment Share on other sites More sharing options...
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