The well known speedometer issues.

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TheZombieNinja3

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Hey guys. It's been awhile since I've been on the Forum or posted or looked around but I've been dealing with the ever known issues with the speedometer on my KJ. I have a 2004 Renegade with manual transmission and when I first got it I had problems with the speedometer and went to a shop to have it fixed and it went well for a few years. Last winter the speedometer started working intermittently and occasionally if I hit a bump it would go off if I had a different bump it would come back on and then eventually all together completely failed. I've read around a bunch of different threads here looking for some answers, and I have changed the sensor on the rear differential and check all the wiring from where the sensor is up into the body of the jeep. I did find cracked insulation in the wire was corroded which I have cut and spliced and after cutting and splicing I'm getting 11.5 volts through the wiring all the way down to the pigtail plug. Still having issues with the speedometer not working and also abs and parking brake light are on. I have not yet replaced the pigtail, but when using a meter the pigtail is also reading back at 11.5 volts. Any ideas as to what I can do?
 

TomB985

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Are they well-known? Now you got me curious! New to the KJ platform. I can help you with wiring diagrams if you like. Send me an email at [email protected] if interested.
 

TheZombieNinja3

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How does the sensor in the diff look, clean and undamaged at the connection?

Not exactly sure what you mean. The sensor itself is brand new and installed yesterday. The multimeter isn't getting anything from the sensor when I look for voltage or ohms. It's possible this sensor was DOA but Being that is a hall effect sensor that I really know nothing about, I don't know how to test it. I did all of this with the back end up on ramps versus on jack stands so being able to spin the wheels freely and try to test it isn't really an option for me.
 

Charlesthe2nd

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Not exactly sure what you mean. The sensor itself is brand new and installed yesterday. The multimeter isn't getting anything from the sensor when I look for voltage or ohms. It's possible this sensor was DOA but Being that is a hall effect sensor that I really know nothing about, I don't know how to test it. I did all of this with the back end up on ramps versus on jack stands so being able to spin the wheels freely and try to test it isn't really an option for me.

When mine was out the sensor had been damaged on the wiring caused by a rub near the brake line. The sensor itself was also gummed up.

Could be that it's DOA. How much have you driven it since the repair?
 

Tin Man

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When I had problems with speedometer the cause was connector in the PCM. It looked ok but didn't lock properly and was missing contact, at least from some pins.
 

TheZombieNinja3

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When mine was out the sensor had been damaged on the wiring caused by a rub near the brake line. The sensor itself was also gummed up.

Could be that it's DOA. How much have you driven it since the repair?

Since splicing the wires and adding a brand new sensor I never got anything out of it, possible it was DOA. I don't know if the sensor itself would have a reading on a meter without being plugged in or in the diff. It's a duralast with a lifetime warranty so I could swap it again.

When I had problems with speedometer the cause was connector in the PCM. It looked ok but didn't lock properly and was missing contact, at least from some pins.

Where does one look to check the PCM? I'm not sure where it's located. And if that is the issue could that still cause the abs/parking brake lights to be on?
 

sota

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Since splicing the wires and adding a brand new sensor I never got anything out of it, possible it was DOA. I don't know if the sensor itself would have a reading on a meter without being plugged in or in the diff. It's a duralast with a lifetime warranty so I could swap it again.



Where does one look to check the PCM? I'm not sure where it's located. And if that is the issue could that still cause the abs/parking brake lights to be on?

so you're saying...
wonky/inoperative speedo
abs light on
parking brake light on
 

Billwill

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You need an oscilloscope to really be able to read the output from the rear diff sensor.

Most problems in that area are with the connector not making good contact on the sensor, the cables nearby chafing onto the parking brake cables or on the chassis somewhere or a broken wire.

The front ABS sensors likewise could have cable damage.

I had a no speedo issue with my 2002 Export CRD...no ABS fitted. Turned out to be a bad connector fitting on the diff sensor. This set the CEL light ON and speedo would go up to about 30 mph max no matter what speed I did.
Once I fixed the connector the speedo worked properly but the CEL light stayed on for about a week....took a couple of start-stop runs for it to reset.

Best to download the correct year Jeep KJ Service Manual here....includes the Wiring Diagrams in Section 8W. I would start with tracing why the Emergency Brake light is ON all the time....may be related to the other problems....then physically check the speed sensor wires for breaks/shorts to chassis. The wires probably disappear into a larger harness where it is hard to physically trace the wires further.

I had about 9 wiring errors on my Jeep after a frontal impact.
The main harness on the KJs goes all the way around the engine bay like the Washington DC Beltway....going through many connectors in the process and on my Jeep going through a solid sqaire metal tube below the radiator...where the damage was done. I had to completely isolate each faulty wire one at a time...disconnecting both ends....including splices...so that the wire was in theory hanging in "mid air".
If I could not them measure continuity from end to end with an Ohm meter....or if I measured a partial leakage to chassis...I would physically cut off all ends of that wire and tape up the ends. Then I replaced this wiring with new wiring...soldering the ends together and using shrink-tubing insulation. I did not try to follow the long round-about journey of for this new wire but took it point-to-point via the shortest route. Then marked my changes on the relevant wiring diagram pages and left it in the glove box for the next Owner!

The Wiring Diagrams will show the relevant wiring colors, splices involved and connectors in line with the route of the wiring. You will need a cheap digital Multi meter.

Also check that the speedometer is actually moving by holding the Odometer reset pushbutton IN while turning ignition ON. The cluster lamps and Gauges should all light up or move around. This is not a diagnostic and does not return error codes.

Jeep KJ Service Manuals: Index of /manuals/Jeep/KJ
 
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TheZombieNinja3

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You need an oscilloscope to really be able to read the output from the rear diff sensor.

Most problems in that area are with the connector not making good contact on the sensor, the cables nearby chafing onto the parking brake cables or on the chassis somewhere or a broken wire.

The front ABS sensors likewise could have cable damage.

I had a no speedo issue with my 2002 Export CRD...no ABS fitted. Turned out to be a bad connector fitting on the diff sensor. This set the CEL light ON and speedo would go up to about 30 mph max no matter what speed I did.
Once I fixed the connector the speedo worked properly but the CEL light stayed on for about a week....took a couple of start-stop runs for it to reset.

Best to download the correct year Jeep KJ Service Manual here....includes the Wiring Diagrams in Section 8W. I would start with tracing why the Emergency Brake light is ON all the time....may be related to the other problems....then physically check the speed sensor wires for breaks/shorts to chassis. The wires probably disappear into a larger harness where it is hard to physically trace the wires further.

I had about 9 wiring errors on my Jeep after a frontal impact.
The main harness on the KJs goes all the way around the engine bay like the Washington DC Beltway....going through many connectors in the process and on my Jeep going through a solid sqaire metal tube below the radiator...where the damage was done. I had to completely isolate each faulty wire one at a time...disconnecting both ends....including splices...so that the wire was in theory hanging in "mid air".
If I could not them measure continuity from end to end with an Ohm meter....or if I measured a partial leakage to chassis...I would physically cut off all ends of that wire and tape up the ends. Then I replaced this wiring with new wiring...soldering the ends together and using shrink-tubing insulation. I did not try to follow the long round-about journey of for this new wire but took it point-to-point via the shortest route. Then marked my changes on the relevant wiring diagram pages and left it in the glove box for the next Owner!

The Wiring Diagrams will show the relevant wiring colors, splices involved and connectors in line with the route of the wiring. You will need a cheap digital Multi meter.

Also check that the speedometer is actually moving by holding the Odometer reset pushbutton IN while turning ignition ON. The cluster lamps and Gauges should all light up or move around. This is not a diagnostic and does not return error codes.

Jeep KJ Service Manuals: Index of /manuals/Jeep/KJ

I exercise the cluster and made sure the gauge actually works and it is moving. For the wires coming from the sensor that were rubbing on the parking brake I have rerouted them so it hasn't been rubbing now and Trace the wire from the sensor to where it goes into the body of the Jeep with no problem and when reading current and continuity of The Wire the end of it at the pigtail still showing 11.5 volts that it's getting the voltage all the way down and I believe the parking brake light being always on is related to the ABS light being on because everytime my ABS light comes on is when the parking brake light goes on but now they're both just permanently on since the speedometer stopped working fully
 

Roberte

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I had my speedometer go out on me just last week and after reading about the wire problem on the 02 liberty. I checked the wires and sure enough it was corroded at the plug. So I replaced the wire and connector it still didn't work. I pulled the rear speed sensor and checked it with my OHM meter and nothing. So I got a new speed sensor and checked it with the ohmmeter and it does show ohm's.
So if yours doesn't show ohm's on your meter it is most likely bad. Check it with the meter and reverse the leads on the post you should get a reading.
 

Billwill

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I had my speedometer go out on me just last week and after reading about the wire problem on the 02 liberty. I checked the wires and sure enough it was corroded at the plug. So I replaced the wire and connector it still didn't work. I pulled the rear speed sensor and checked it with my OHM meter and nothing. So I got a new speed sensor and checked it with the ohmmeter and it does show ohm's.
So if yours doesn't show ohm's on your meter it is most likely bad. Check it with the meter and reverse the leads on the post you should get a reading.

Yes I seem to recall that I also got a resistance reading on my sensor but that was way back in 2002 soon after picking up the Jeep!
Definitely worth checking!
 

TheZombieNinja3

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Well I was back under the Jeep today, replaced the pigtail plug to the rear diff sensor, no luck :( before replacing the plug today yesterday on my drive to work the speedometer turned on for about 2 seconds and then shuts back off again. Any ideas? I'm getting a vehicle speed sensor a code as well
 
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