Speedo/Odometer quit!!, however....

[airtractor]

all functions such as cruise (set, coast, resume, etc), auto door locks, transmission works/shifts exactly as before (perfectly). No ABS light or warning lights. The only items that I can relate to this event is that while on a mission to find which computer has the factory PIN code posted on the outside for the keyless entry, I removed the ECU/PCM at the firewall, re-connected the 104 pin connector and then noticed the speedo/odometer was in-op. I have stripped back the outside wrapping to look for a bare wire and traced out the multi-wire harness from the ECU/PCM plug to the dash plug-ins without finding a problem. Full voltage and good ground to the cluster plug in. While the cluster was out, I removed the speedo/odometer and took to a speedo shop to verify operation only to find that was not the problem either. No broken traces on the back of the cluster case. Cleaned all pins and plugs. Apparently all is well up to and inside the ECU/PCM till it comes to the output to the speedo/odometer?? Trying to find a used 96 5.0 ECU/PCM with the correct software version, axle code, emission code, etc. first rather than start throwing big $$$s at this unknown or is there something obvious I'm overlooking?? Appreciate any feed back without tech stuff that is over my head. Thanks, Bob

 

[gijoecam]

Check Fuse #25 (7.5A) in the Fuse Junction Panel. The ECU doesn't tie into the speedo.... the speedo input is powered from that fuse, and the input for the actual speed comes from the 4 wheel ABS module. (specifically the gray with black striped wire)

As for the door code, it's on the PATS module in the jack storage compartment. Pics are in my gallery in my signature under the "Pats Module Location" in the pull-down.

-Joe

 

[airtractor]

Thanks Joe,

The fuse at #25 was the first item checked last week. It is almost a "no brainer" as this circuit also is the door chimes and interior lights (both work), but to make sure I replaced the fuse anyway. Out of desperation I replaced the VSS at the transmission this weekend, no change. The only gray w/black wire that I find is at pin #58 on the ECU/PCM connector. It is tight and shows to not be grounded. Keep hitting me with some suggestions, PLEASE!!

I'll assume by your use of the word "input", that is also the "pulse generated by the senor"??

Not that it would change anything, I'll make a note that this '96 is a 2WD.

The ABS sensor at the rear axle, per my understanding, has no connection with the speedo/odometer. I had that sensor go bad on my '99 AWD Limited last year and there was no effect the speedo.

Yes, I found the PATS code after reading your earlier post last week. Thanks, should have read this first rather than go on a blind hunt earlier last week.

Still attempting to find a ECU/PCM from a donor '96/'97 5.0 car just to check. Even though the speedo and odometer worked on the bench at the speedo repair shop, I may gamble with one off of eBay and try it.

I'm trying every avenue before going to the Ford store and being crucified. All they will do is probably duplicate what you and I are doing. To my knowledge, an in-op speedo will not show as a "fault code".

Thanks, Bob

 

[gijoecam]

My bad... I thought we were talking about a '99 and looked up the wrong diagram for it.

I had to mention the fuse.... you'd be surprised how many people overlook the obvious, or don't realize there's two different boxes with fuses on their truck. Nothing personal...

For the '96 in question, the signal wire from the VSS is supposed to go direct to the cluster via the gray with black wire. If it's an early-model and shares the wiring with the '95, I can't be of much help, but even if it's a late model and shares the wiring with the '97 model year, there should still be a gray with black striped wire going into the cluster. I can't seem to find the pinout for that connector though....

And yes, you are right.... I didn't look far enough down the diagrams, but that same 7.5A fuse would also kill the GEM module too.

[side-bar here] Yes, the speed sensor on the '99 limited is not directly tied to the speedo. The vehicle still knows its speed from the front wheel speed sensors. The ABS module takes the info from the speed sensor, determines the vehicle's speed, then sends that signal to the Speed Control Servo, PCM, instrument cluster (speedo), GEM, Message Center, Radio, Air Suspension Control Module, and the Compass/outside air temp module. All of those connections are via the same GY/BK wire fed from the ABS module.

Useless info for the problem at hand, I know.....

For the '97, it appears that the onlu thing the VSS is connected to is the speedo. It generates an AC voltage that causes the speedo to raise. The only way I can think of to test it would be to disconnect it and check for voltage coming out of the VSS while underway. If the VSS is dead, that would explain the lack of speedo. If the VSS is outputting an AC signal like it should, the speedo is toast.

Hope that helps!

Joe

 

[airtractor]

Again, appreciate your attention and help Joe.

Good news is that this is an April '96 Explorer. Regarding the VSS at the transmission, I installed a new one yesterday. However, I will disconnect the factory plug and make a temporary conncetion/harness from the new VSS to my hand held AC meter and drive the car.

Assuming that there is an "output" from the newly installed VSS, I have another "plan". I bought today a complete instrument cluster from a '97 Explorer with a 4.0. From my EdmundsOnDemand drawings the 5.0 and 4.0 have a different resistance value at the tach. Therefore, I'll utilize only my original tach and the newer '97 speedo/ododmeter with the complete cluster and housing. Unknown how or when, there may be a broken trace on the back of the housing (plastic sheet). Your thoughts??

Also for your and my info, I'll trace out the gry/blk from the VSS to the dash for confirmation of the pin location when I get the '97 cluster ready in a few days.

Keep 'em coming at me, I need the brain exercise.

Bob

 

[Jefe]

One thing you could check: Use an OBD-II scanner and see if the PCM is getting VSS. However if it isn't I think you would notice your transmission acting differently. (I know on the V6 auto trans it is obvious when the PCM looses VSS)

 

[boominXplorer]

i thought in 96 and 97 the sensor in the tailshaft controled the speedo?

 

[Jefe]

i thought in 96 and 97 the sensor in the tailshaft controled the speedo?

It does.

 

[airtractor]

To Joe, Jefe and BoominXplorer.

I disconnected the feed harness from the VSS and made a temporary harness to my voltage meter. Drove about 1/2 mile and without a doubt the VSS is generating a pulse or signal that varies directly with vehicle speed. And yes, the transmission acted "funny" when un-hooked. Hooked the VSS back up, drove it again. Nothing funny!!

Joe indicated earlier that the VSS signal goes directly to the speedo/odometer per his drawings on a '96/'97, not directly to the ECU/PCM (does it go "indirectly"??). I can't confirm either; however I would think that vehicle speed info of some type is needed by the ECU/PCM.

I welcome any other suggestions by anyone if there is something else external to suggest to check. Next for me is to wait till I get the '97 cluster in, diisassemble the dash again, find the VSS feed pin (per Joe a gry/blk wire) and then check the signal at the dash prior to installing the '97 speedo/odometer. I've done about all I can do short of handing the Ford dealer the Explorer and my check book.

Standing by!!

Bob

 

[gijoecam]

Joe indicated earlier that the VSS signal goes directly to the speedo/odometer per his drawings on a '96/'97, not directly to the ECU/PCM (does it go "indirectly"??). I can't confirm either; however I would think that vehicle speed info of some type is needed by the ECU/PCM.

Indeed it would seem so. It would make sense that the signal needs to get there eventually, but the '96 schematic didn't appear to show it.

Hmmm.... I'll have to stare at the schematics again in the morning.... It wouldn't be the first time I missed something. The early schematics for the '96-'01 leave a lot to be desired.

-Joe

 

[gijoecam]

Indeed, after digging deeper, the VSS does appear to connect to a whole bunch of other components.... It's not reflected on the schematic for the instrument cluster like it is in the print for '99.

The VSS is also connected to the speed control servo, PCM, Automatic Ride Control (if so equipped) and the instrument cluster. However, like the '99 I mentioned above, they are all indicated as a gy/bk wire. Given your experience yesterday, I'd say that it's a pretty safe bet that they VSS isn't the culprit. The only thing left to try is the wiring to the IP or the speedometer itself.

I'm still pretty sure it's just coincidence that it occurred when it did though.

-Joe

 

[airtractor]

Joe,

I was able to verify that the gry/blk wire from the VSS feeds info to pin #58 (gry/blk wire) at the ECU/PCM. I found no other points on this 104 pin connector that is fed this info. Therefore, I assume that the speedo info is fed directly to the speedo from the VSS or the VSS info is a simple in/out (pass through) via the ECU/PCM. I prefer to not check any pin outs to the dash for fear of causing some internal damage to the ECU/PCM.

Till this other cluster arrives tomorrow or the next day, I'll wait to dismantle the dash.

Appreicate the help.

Bob

 

[airtractor]

Joe,

The new speedo/odometer was not the cure. Rechecked and re-verified every contact point for continuity and contact from the ECU/PCM plug-in to the dash connectors to the back of the speedo/odometer. Until there is something else that comes to mind from someone, best that I drive the Explorer with the in-op speedo.

The list for the exchange ECU/PCM at Ford is about $270 exchange. Obviously, if purchased "over the counter", it can not be returned for any reason including an out of the box failure. Better to pay retail part price and labor via the service dept. at the Ford dealership and let them wear the responsibility of it failing again is one option.

Trying to find a used ECU/PCM for a '96 5.0 with the correct calibration codes is proving more difficult than I thought.

Searching the net for ECU?PCM repairs, I find at least two. One is about the same price as Ford and the other is much less. I'm sure Ford uses one of these repair facilities and sticks their label on it.

Appreciate everyone's help.

Bob

 

[n0xdw]

Joe,

The new speedo/odometer was not the cure. Rechecked and re-verified every contact point for continuity and contact from the ECU/PCM plug-in to the dash connectors to the back of the speedo/odometer. Until there is something else that comes to mind from someone, best that I drive the Explorer with the in-op speedo.



Searching the net for ECU?PCM repairs, I find at least two. One is about the same price as Ford and the other is much less. I'm sure Ford uses one of these repair facilities and sticks their label on it.

Appreciate everyone's help.

Bob

Just a word, from what you are describing the ECU will not be the culprit. The VSS signal does go to the ECU from the ABS, but as you pointed out the transmission shifts properly, and Speed control still works. This signal is provided by the ABS and there is are 2 splices (S247 and S168) where the signal splits to go from the ABS to the speed control, the ECU and the speedometer as well as the radio the GEM and others. Verify the gray/black wire at the back of the cluster has continuity to pin 3 at the speed control harness, or pin 9 of the radio, or you could check at the GEM. Even the compass/temp module gets this signal. But the speed control connector is easy to get to, and the radio should not be difficult and would also be under the dash. It will be the gray/black color at all locations so I would probably check from pin 1 of the cluster (C287 12 pin black connector) to either the radio or speed control harnesses. if you do not have continuity which i suspect is the case then check splice S247 near the cluster. IE simply follow that gy/bk wire back to the harness and look for damage there. I would probably choose the speed control as you know it has the signal, but then you will need a long jumper wire to inside. If that splice is good but does not have continuity check pin 20 on both sides of connector C146 I believe that is the top one of the 3 pass through connectors left side between engine compartment and inside the cab. Fact it might be a good place to start to verify continuity from speed control to there first. Also make sure the bolt holding the connector together is tight. GL
1985 B2 with a 1999 4.0 with PATS engine (that is why i am familiar with the 99 i have the factory service information for 99)