2nd Gen Non-Engine/Transmission Speedo. Died, Suggestions?

[JesseJ]

So my speedometer started going goofy a couple days ago, bouncing around then sitting on zero then it would come back up then die again and it finally died for good. Of course with no speed the ABS and Brake warning came on in the dash. I figured the speedo. Sensor in the rear axle was bad so I replaced it and that didn't fix it. has anybody come across this problem before? Did my dash cluster die?

 

[n7gxz]

There is a way to run the cluster throught a self test. I don't remember right off hand but it is in the service manual. If it checks out OK then it is either the ABS controller (if you have 4 wheel ABS) or the PCM.



Kevin

 

[JesseJ]

No 4-wheel ABS, just in the rear. No service manual either. Anybody know how to do the self-test?

 

[SmithS]

check the rear end sensor wires, mine rubbed on the brake lines and did the same thing, just had to solider the lines and heat tape. Also put one flexiblie tubing so it would happen again.

 

[Dave M]

I found a Stored DTC code test at this site for 94-96... not sure if it will work on a 99:

94 Diesel Ram DTC's





Here is another "Official" procedure to check out the instrument cluster and CODES I found... . not sure if it works past 98:

SELF-DIAGNOSTICS

1) With ignition off, press and hold trip odometer RESET

button while turning ignition switch to ON position. Continue to hold

RESET button until odometer window displays CHEC (approximately 10

seconds). If problem exists, system will display Diagnostic Trouble

Codes (DTC). See DIAGNOSTIC CODE CHART table. For repairs of DTCs, see

BODY CONTROL COMPUTER TESTS in BODY CONTROL COMPUTER article.

DIAGNOSTIC CODE CHART TABLE

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ÄÄÄÄÄÄÄÄÄÄ

Code Description

110 ... ... ... ... ... ... ... ... ... ... ... Cluster Memory Fault

900 ... ... ... ... ... ... ... ... ... ... ... . CCD Bus Inoperative

920 ... ... ... ... ... ... . Not Receiving VSS Message From PCM

921 ... ..... Not Receiving Distance Pulse Message From PCM

940 ... ... ... ... ... ... ..... Not Receiving Air Bag Light On

Message From Air Bag Module

950 ... ... ... ... ... ... ... ... ... Not Receiving ABS Light On

Message From Anti-lock Control Module

999 ... ... ... ... ... ... ... ... ... ... ... ..... Undefined Error



2) If DTCs appear, cluster will start a walking segment test.

First all segments will be illuminated, then each segment in sequence.

If any segment does not illuminate, confirm test and replace

instrument cluster. When walking segment test is complete, bulb check

will start.

3) If any bulb does not light, remove instrument cluster and

check bulb and bulb holder. See INSTRUMENT CLUSTER R & I. If bulb and

bulb holder are okay, replace instrument cluster. If LED does not

light, replace instrument cluster. When bulb check is complete, gauge

actuator test will start.

4) Each gauge needle should stop at 3 calibration points,

then return to relaxed position. If any gauge does not perform as

specified, remove instrument cluster. See INSTRUMENT CLUSTER R & I.



Inspect all connections between printed circuit board and gauge

terminals, repair as necessary. If connections are okay, replace

instrument cluster. Instrument will automatically exit self-diagnostics

when test is complete.



NOTE: There are 2 instrument cluster connectors. These connectors

are exactly the same. Ensure wire colors are correct during

all testing procedures. See WIRING DIAGRAMS.

I'm not sure if it works for a 99.



Dave

 

[Dave M]

I found more code procedures here:

https://www.turbodieselregister.com...mission-faq/96261-checking-codes-2000-up.html



Here is a copy of the above link:

Checking for codes on 2000 & up

------------------------------------------



Bring a pencil and paper to write down the numbers.



Key in the ignition, engine off



Turn the ignition to the run/on position (do not start)

Back to off

On

Off

On and leave on. Leave the ignition in each position at least 3/4 of a second. If you are too fast, or too slow, it will not complete the cycle.



In the odometer window the on board computer will show two sets of codes



Go to 2nd gen FAQ on this site to find code listings.

Dave

 

[Dave M]

I'm sure you guys are sick of me by now but here is a link for getting codes from 98+ with a copy of it:



98+ Ram Instrument Panel Test



From that link above:

1998+ instrument clusters have a self diagnostic test you can run for your enjoyment and information.



Begin with the key off and vehicle stopped.

Depress AND HOLD the trip odometer reset button and turn the ignition switch to the ON position BUT DO NOT START THE TRUCK.

Continue to hold the reset button in for about 10 seconds until "CHEC" appears in the odometer display, then release the button.

A series of 3 digit error messages MAY appear in the display (IF you had cluster problems) but if not then the display will proceed with the segment test; all segments then each individual segment in sequence will illuminate. If any do not, the cluster is a candidate for service. If all are OK then the next test follows.

The bulb of each amber indicator lamp that the cluster controls will light individually, if not, the bulb may be bad, the bulb may be loose or the bulb holder may not be installed correctly. The red indicators are LED's and if they don't light in the test the cluster must be replaced.

The gauge actuator test is next. The cluster circuitry will position each of the gauge needles at three different calibration points and then return the needle to its relaxed position. If any one does not respond correctly, check the spring-clip terminal pins on the cluster. If those are OK the cluster is bad.

The self-diagnostic test is completed. The cluster will self exit the test mode and return to normal at the end of the test. If the key is turned off during the test or if the PCM sends a message on the CCD bus that there is movement of the vehicle, the test ends. Try it!

INSTRUMENT CLUSTER FAILURE MESSAGE

Message Description Correction

110 A failure has been identified in the cluster CPU, RAM, or EEPROM. 1. Replace the faulty cluster.

900 The CCD data bus is not operational. 1. Check the CCD data bus connections at the cluster.

2. Check the cluster fuses.

3. Check the CCD data bus bias.

3. Check the CCD data bus voltage.

3. Check the CCD data bus terminations.



920 The cluster is not receiving a vehicle speed message from the PCM. 1. Check the PCM software level and reflash if required.

2. Use a DRB III scan tool to verify that the vehicle speed message is being sent by the PCM.



921 The cluster is not receiving a distance pulse message from the PCM. 1. Check the PCM software level and reflash if required.

2. Use a DRB III scan tool to verify that the distance pulse message is being sent by the PCM.

940 The cluster is not receiving an airbag lamp-on message from the ACM. 1. Check the CCD data bus connections to the ACM.

Check the ACM fuse.

950 The cluster is not receiving an airbag lamp-on message from the CAB. 1. Check the CCD data bus connections to the CAB.

Check the CAB fuse.

999 An error has been discovered. 1. Record the failure message.

2. Depress the trip odometer reset button to continue the

Self-Diagnostic test.

And one other link:

24V Troubleshooting



Good Luck,

dave

 

[JesseJ]

All good info. Dave, thank you! I'll have to print it out and start in on it tonight after work. I already checked for broken wires and such, that was my first thought w/ so many miles on it but I didn't find anything broken or rubbed so, who knows.

 

[ox1]

Been a few weeks - got it fixed yet?

What was it?

Mine has been giving me fits for a yr or two - but only on damp and especially cold/damp days.

???


ABS light burnt out a few yrs ago and the brake [dash] light has been on now for aboot 175K. :-laf Hoping it gives out SOON!

 

[JesseJ]

Still don't have it fixed. I tried all the code reading as suggested above but it showed nothing, everything worked normally.



My next venture is trying to replace the harness. I had a 2000 1-ton van totalled out and the harness is in perfect shape. I'm going to see if I can splice/replace as much of that harness as possible in hopes of replacing the bad part that I can't seem to find. I think the two harnesses are very similar for most of it so we're going to try it and cross our fingers. Wasn't really in the mood to do it today, 100+ and 75% humidity outside didn't make me too motivated to work on it. I like AC.

 

[GAmes]

Have you tried a new speedometer? Pretty easy to replace on a 97, I don't know about yours. The needle is powered by a small motor and they do fail. Mine did.

 

[JesseJ]

I think that was the whole point of the tests mentioned earlier by previous members. The 3x Key on key off trick will take it through a functional test and it checks to make sure all the gauges are working at 0 midrange and max. If that is the problem, I'm thinking I'll have to replace the whole dash cluster which is easy but probably not cheap. I guess I'm still leaning towards the wiring because there's a hundred different places it could rub or bounce around and break the wiring in the insulation and I have a lot of miles on my truck. I'll probably disconnect the harness on both ends and check resistance before I tear it out.

 

[fest3er]

I think that was the whole point of the tests mentioned earlier by previous members. The 3x Key on key off trick will take it through a functional test and it checks to make sure all the gauges are working at 0 midrange and max. If that is the problem, I'm thinking I'll have to replace the whole dash cluster which is easy but probably not cheap. I guess I'm still leaning towards the wiring because there's a hundred different places it could rub or bounce around and break the wiring in the insulation and I have a lot of miles on my truck. I'll probably disconnect the harness on both ends and check resistance before I tear it out.

Holding the reset button and turning the key on, then releasing the button when the self-test starts should cause all the gauges to be tested from minimum to maximum positions. If the gauges work during the self test, the cluster is OK.



Put the truck up on blocks, put it in gear and let it idle to whatever speed it wants to get to--anything over 10-15MPH should be fine. Then measure the voltage (AC, not DC) at the CAB end of the rear speed sensor. You should see something in the range of 1-3 volts. (A sillyscope would show this better. ) If you see very low voltage (. 5 or less), you'll have narrowed the problem to that harness or the rear sensor.



If you see decent voltage, then check to see if a reasonable signal is being sent to the PCM. If the CAB's gazinta signal is OK, but the gazoutta signal is missing, the CAB may have failed.



It is not impossible that the CAB (Controller, Antilock Brake) has failed. Mine died some years back. I replaced it and all was well again. If you do replace it, be absolutely sure that you get the right one. The one I got isn't quite right: the ABS light has been flashing at me for 100K miles now and the CAB refuses to be programmed--I can't set the tire rev per mile setting, which is OK since my TruSpeed module is far more accurate. I just ignore the light, because the RWAL brake and other things are working just fine.

 

[JesseJ]

Yeah I did that test and it tested all the gauges from min to max, all was ok. I replaced the sensor first, thinking that would take care of it. I have noticed though that before it was screwing up all the time, now it's fine until I get above 35 MPH then it starts to go all goofy.

 

[fest3er]

Yeah I did that test and it tested all the gauges from min to max, all was ok. I replaced the sensor first, thinking that would take care of it. I have noticed though that before it was screwing up all the time, now it's fine until I get above 35 MPH then it starts to go all goofy.

So the cluster is OK. If you can see the teeth inside the rear diff, you might verify their condition; sometimes they can get chewed up unexpectedly.



Unplug all the connectors on the CAB and verify those connections are OK (clean and dry). Verify the connections in the three PCM connectors are clean and dry as well.



If you can, find someone with an oscilloscope so you can see the waveforms going into and out of the CAB. They should be solid and steady at any speed over 5 MPH, varying only with wheel speed. If the sensor is solid and steady but the signal to the PCM is bad, the CAB is definitely the problem.



One last thing to check is the ground connection from the CAB to the body. Generally between the CAB and the fender, you'll find a ground connection point. Remove the wires and wirebrush everything. Then reassemble using a bit of dielectric grease on the connections. There's a small change the CAB doesn't have a good ground. And if that ground is bad, check the rest of them (battery to body, engine to body, et al). Lousy grounds cause more electrical problems than you can imagine!

 

[JesseJ]

Ok, what is the CAB and where is it located? I wish I had wiring diagrams to see how they laid it out. If the signal from the sensor splits to go to the dash and the antilock brake thing then I would assume it's bad wiring somewhere. Also a possible bad ground, that could always be a possibility. If the signal goes through the antilock brakes and then to the speedo then I suppose it could be bad.

The whole thing sucks because I'm getting ready to move a week from Fri. and have way too much on my plate besides this. The other problem though is that I won't have a shop to work on my stuff when I get out there so I kind of need to get this figured out now before I do leave.

 

[fest3er]

Note that the attached images are for my '98. The '99 should be fairly similar. But be aware that the wiring might use different colors.



See the attached pictures. The CAB is, if I may use the term, the black box located near the rear driver's side of the engine compartment, kind-of in the brake lines.



The speed sensor is not split between the CAB and the PCM. The CAB reads the variable-voltage differential signal from the sensor and 'translates' it into a constant-voltage signal that it feeds to the PCM.



When my CAB died, the ABS and brake lights came on and the speedo/odo stopped working.

 

[JesseJ]

Awesome picture and wiring diagrams, thank you! So I have another question for you then, can you just replace the black box or does the whole thing, solenoids and whatever else is attached to that have to be replaced all at once? Where did you go for your replacement? Did you just get it out of a junk yard piece or go to the dealer? Mine is doing the same thing you described. ABS and Brake lights come on, speedo. will work up until about 35 MPH. Anything above that either kills it completely or makes it bounce all over. Unfortunately I won't have the time to do anything with it until Saturday. That's when I'm planning on attacking my truck and getting it all done before I move. I will report back when I have more info. If anyone has other ideas/suggestions in the mean time I'm all ears!

 

[fest3er]

... So I have another question for you then, can you just replace the black box or does the whole thing, solenoids and whatever else is attached to that have to be replaced all at once? ...

The black electronic box is replaced by itself. Unplug the connector, unscrew the box, replace it, screw it in, plug the connector back in and it should be ready to go. (Hmmm. IIRC, there is another set of pins which connects to the ABS hardware, but this is where it mounts to the fluid controller.



It's probably a dealer item; I don't see anything on a google search. But be explicit when you order the part. Bring the truck, let them get ALL of the info they need to order the correct, matching part. And be sure you get a no-questions-asked return policy with it. If they sell you a controller that your PCM and their diagnostics systems cannot program, they must take it back. Unless, of course, you can easily ignore the flashing ABS light for the next 10 years.



N

 

[JesseJ]

This raises another good question then: Can I also rob this black box off of the totalled 2000 1-ton van I have free access to parts to use and put it on my truck? It would be worth a try wouldn't you think? Maybe just maybe I could get lucky and it would fix everything, no lights flashing. Free is a darn good price not to at least try right? It had rear ABS only just like my truck, same sensor and mostly the same harness, I wonder if it's possible they'd be close enough to do it. Sounds like I'm going scavenging again tonight.