2002 Tahoe....no speedo and no tach - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 11-22-2015, 06:37 PM   #1
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Default 2002 Tahoe....no speedo and no tach

I replaced the transmission in a 2002 Chevy Tahoe due to the old tranny went bad.

Now that I have the repklacement transmission installed, there is no speedometer doesnt work, nor does the rpm guage.

I didn't mess with the engine at all, so I dont really understand the tach problem....

What electrical socket is on the transmission that indicates mph.
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Old 11-22-2015, 07:04 PM   #2
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Wait, you replaced the transmission? With what? Where did it come from?

And yet, you can't figure out why you have no speedo or tach? And you want us to figure that out for you? This is exactly why mechanics at shops role the eyes at customers. Because they gone done something they had no clue as to what the hell they were doing.

Retrace your steps to see what you left disconnected.
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Old 11-22-2015, 07:31 PM   #3
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The transmission already had problems slipping under heavy load. The trans fluid was really burnt....the fluid color was almost black.

The transmission has definately been needing to be swapped out for the past 6-8 months.

I installed a rebuilt transmission from a reputable trans rebuild shop.

Speedometer and tach used to work right up until I removed the bad trans.

UPDATE: I found the tach wire socket was unplugged......I plugged it in and now the rpm guage is now working.

As for the mph guage, I still have nothing. I know the sensor furthest back on the passenger side of the transfer case is the speed sensor. (this is a 4x4 2002 Chevy Tahoe). Anyhow, on that portion of the wire harness, there are 3 connectors that are identical.....two of those wire connectors can reach the speed sensor. I don't know which is which. I should have noted thier location prior to removal (but I assumed all connectors in the same section of the wire harness, have unique shapes preventing them from coupling with the wrong sensor).

I would not have swapped out the whole transmission to fix a speedo problem. (I've rolled my eyes more than a few times when I hear someone swaps out a major component $$$ in hopes of fixing a low dollar repair....)

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Old 11-24-2015, 01:28 PM   #4
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Ok, so this is what I have done in my quest to find out why the speedometer is not working:

Pulled and checked all fuses for continuity. All fuses are good.

I pulled the speed sensor off my 2002 Chevy 4x4 truck (same part#) and installed it onto the 2002 Chevy 4x4 Tahoe. After I installed the speed sensor onto the Tahoe, the Tahoe speedometer still did not work. I installed the Tahoe speed sensor onto my truck and the truck speedo worked. So I now know the Tahoe speed sensor is good.

I installed my 2002 Chevy truck 4x4 pcm into the Tahoe, did the security relearn procedure, the Tahoe would run fine but still the speedometer was not working.

I installed the Tahoe pcm into my Chevy truck performed the security relearn procedure, the truck ran fine and the speedo worked. Now I know the pcm is good.

Thinking the speedometer guage itself may be bad, I connected my laptop computer to the DLC......I took the Tahoe for a short drive and noticed that my laptop displayed ZERO mph. So I am assuming the pcm is not getting a speed input signal.
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Old 11-24-2015, 04:50 PM   #5
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Which PCM is it? 0411 ?
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Old 11-30-2015, 09:23 PM   #6
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Well, I feel like an idiot.

I got the transmission working properly. The section of wire harness that connects onto the transmission has 5 identical electrical plugs.

3 on the transfer case
1 on the trans harness which plugs into a female socket which then plugs onto a 5th identical socket.

I got everything one correctly except I overlooked one of these sockets at the top of the transmission.

Now I am going to do another swap on a 2001 Yukon........same 5.3 and 4L60E transmission..........definately gonna keep the harness in mind this time around.

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