The well known speedometer issues.

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TheZombieNinja3

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After changing the pigtail still no luck. Might have to bite the bullet and take it to a shop, still throwing a code for vehicle speed sensor a as well.
 

TheZombieNinja3

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So I had it at a mechanic and he's telling me that even though I replaced the sensors in the wires and everything the computer is stuck and I need to have a computer flashed at a dealership. Does this make sense to anyone?
 

tommudd

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So I had it at a mechanic and he's telling me that even though I replaced the sensors in the wires and everything the computer is stuck and I need to have a computer flashed at a dealership. Does this make sense to anyone?

I have worked on the wiring, sensor, swapped diffs, etc on 02s, 03s 04s and 05s and never had to have the computer reflashed . Now with that said, not saying you do have to go do that but have never heard of it or experienced it . I've worked on at least a dozen or more with speedo issues and after finding issues, repaired and all was great
 

TomB985

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I don’t have Tom’s breadth of experience, but I tend to agree. I don’t think I’ve ever heard of the PCM reset needed for something like this, it just doesn’t make any sense to me.

The system sees a voltage from that wire or it doesn’t, what exactly are they going to reset? It doesn’t “learn”the circuit has failed and need to be taught that it’s working again, they’re just not that smart (or stupid).
 

TheZombieNinja3

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I have worked on the wiring, sensor, swapped diffs, etc on 02s, 03s 04s and 05s and never had to have the computer reflashed . Now with that said, not saying you do have to go do that but have never heard of it or experienced it . I've worked on at least a dozen or more with speedo issues and after finding issues, repaired and all was great

I don’t have Tom’s breadth of experience, but I tend to agree. I don’t think I’ve ever heard of the PCM reset needed for something like this, it just doesn’t make any sense to me.

The system sees a voltage from that wire or it doesn’t, what exactly are they going to reset? It doesn’t “learn”the circuit has failed and need to be taught that it’s working again, they’re just not that smart (or stupid).


I haven't gone to get a pump reset done yet but something interesting has started to happen. More and more frequently now the speedo will kick one for a few seconds at a time, not reading accurately and when it does its feelstill like the jeep is stuttering like it's being starved for fuel. I think I mentioned earlier that codes reading back are also saying it's running too rich and too lean at the same time. I'm running out of ideas here
 

Aceofspades

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If you have any obd2 readers you can check your speed while driving and compare it to the cluster. When the cluster cuts out see if the scanner does too. Maybe it’s s fault in the gauges.
 

uss2defiant

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did u try Ace's suggestion w/ using an obd2 reader for speed?
i guess a long shot suggestion is to have the rear on jackstands and see if the issue persist.
I wonder if there is a short occurring with the vehicle moving.
 

Billwill

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Wiring errors on these Jeeps are a major problem to find. The wire harness goes all the way around the engine bay so that even if there are two points connected that are 18 inches away....they take the long route around the Jeep of about 8 feet with connectors inline and the chance of scrapping down to chassis/engine somewhere or shorting through to another random wire within the harness somewhere.

I had to track down about 9 wires shorting to chassis or to other wires somewhere within the harness. The Dealers here were totally useless but fortunately I know my Electronics!
 

TheZombieNinja3

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did u try Ace's suggestion w/ using an obd2 reader for speed?
i guess a long shot suggestion is to have the rear on jackstands and see if the issue persist.
I wonder if there is a short occurring with the vehicle moving.

I have no idea what an odb2 reader is, or how to use it.
 

LightScout03

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I'm having the same problem.

Got into a jam and had to get an 05 KJ Rocky Mountain Edition, that had the speedo issue when I bought it(Stupid I know) because I thought it would be relatively simple change pig tail, and sensor and should be good to go. Nope...

So I've tested the voltage using an inexpensive multimeter-analogue, and voltage through the new pig tail is 11 volts. With the rear wheels up and secured, I tested the volts on the signal side of the sensor 1volt regardless of in motion or not.

I have also checked up at the BCM, same 11 volts on the power supply to the sensor and on the signal wire side is 1 volt just like at the sensor. I then tested speed signal from the BCM to I'm assuming the PCM and it was 4.5 volts.

So I know that power is getting to the sensor, that at least some and the same voltage is on the signal side of the speed sensor. I also know that the BCM is working to transmit the information it receives. What else am I missing? Is the signal side voltage to weak?

Also I did the diagnostic of the cluster its self.
 

Billwill

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@LightScout03.

I believe that on the 2005 the speedo needs both the output from the diff sensor and the ABS sensors to work.....so the ABS sensors may have an issue!

You have changed the diff sensor but for general information there was a TSB issued years ago by Chrysler that all 2005 KJs had their diffs filled with the wrong oil. This oil chewed up the diff sensors. The fix was to take the Jeep to the Dealers who would drain the rear diff oil, clean out the diff, fill with the correct oil and fit a new sensor.

The only way to test the diff sensor is with an oscilloscope as mentioned.

You would otherwise have to test all the wires going to the diff sensor and ABS sensors with a multi meter to check for continuity and for shorts or partial shorts to chassis...download the 2005 Jeep KJ Service Manuals here...section 8W has the wiring diagrams and the Service manuals have some theory of operations information on how the speedometer operates.

KJ Manuals: http://www.colorado4wheel.com/manuals/Jeep/KJ
 
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TheZombieNinja3

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Well unfortunately I will no longer have to continue to chase this issue. Last night my kj got totalled. Will make a separate post about that right now. But the funny thing is, 3 miles before it happened the speedo started working, and read accurate and was counting miles. Then bang, the kj was done. I'm totally fine with zero injury
 

LightScout03

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@LightScout03.

I believe that on the 2005 the speedo needs both the output from the diff sensor and the ABS sensors to work.....so the ABS sensors may have an issue!

You have changed the diff sensor but for general information there was a TSB issued years ago by Chrysler that all 2005 KJs had their diffs filled with the wrong oil. This oil chewed up the diff sensors. The fix was to take the Jeep to the Dealers who would drain the rear diff oil, clean out the diff, fill with the correct oil and fit a new sensor.

The only way to test the diff sensor is with an oscilloscope as mentioned.

You would otherwise have to test all the wires going to the diff sensor and ABS sensors with a multi meter to check for continuity and for shorts or partial shorts to chassis...download the 2005 Jeep KJ Service Manuals here...section 8W has the wiring diagrams and the Service manuals have some theory of operations information on how the speedometer operates.

KJ Manuals: Index of /manuals/Jeep/KJ

Thanks for the advice. I took care of the TSB prior to changing the sensor on the diff. Also my vehicle does not have ABS, wasn't standard until 2006 so there is no ABS control body on the jeep. I checked the continuity like I said, but today for grins and giggles I pulled fuse 34, started the jeep and the speedo moved on its own like a pre-start test, still no speed but makes me think that it might be the BCM, hooking up a flashed PCM didn't help.
 

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