My speedometer is fixed
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From: Longview, Tx
My speedometer is fixed
Well, I finally got around to messing with it, turned out to be a short in the VSS wiring. Here's what I did and how I narrowed it down. (Due to model variances, I can only say that this is 91/92 specific....other years had different VSS and speedometer setups)
Symptoms, Speedometer doesn't work and torque convertor doesn't lock up, occasional VSS code.
The computer controls TC lockup, but will only do it if it sees 35 MPH, so since it's not locking up, then it's not seeing 35 MPH, meaning that the actual speedometer is ok, leaving one of 3 problems. 1. Short in the wiring between VSS and ECM. 2. VSS buffer inside the ECM is bad. 3. VSS is bad.
Considering I already replaced the VSS as my first step at a solution, I knew it couldn't be 3. Since an entire ECM is costly, I decided to try 1. Color of the wires for the VSS connector is Yellow and Purple, which is the same going into the ECM. So I cut the connector off, and cut the wires going into the ECM off, drilled a hole in my trans tunnel, and directly ran wires from the VSS connector to the ECM. Get in car, start up, drive and for the first time since April, my car goes above ZERO.
Symptoms, Speedometer doesn't work and torque convertor doesn't lock up, occasional VSS code.
The computer controls TC lockup, but will only do it if it sees 35 MPH, so since it's not locking up, then it's not seeing 35 MPH, meaning that the actual speedometer is ok, leaving one of 3 problems. 1. Short in the wiring between VSS and ECM. 2. VSS buffer inside the ECM is bad. 3. VSS is bad.
Considering I already replaced the VSS as my first step at a solution, I knew it couldn't be 3. Since an entire ECM is costly, I decided to try 1. Color of the wires for the VSS connector is Yellow and Purple, which is the same going into the ECM. So I cut the connector off, and cut the wires going into the ECM off, drilled a hole in my trans tunnel, and directly ran wires from the VSS connector to the ECM. Get in car, start up, drive and for the first time since April, my car goes above ZERO.
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Joined: Jul 2001
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From: BFE, MD
Car: 13 Ram 1500/ 78 Formy
Engine: 5.7 / 7.4
Transmission: 6sp / TH350
Axle/Gears: 3.55 posi / 3.23
and who says procrastination doesn't pay 
now you get the option of driving by the speedo or tach again. My dash lights won't come on, nor will the volt meter gauge work., maybe it needs a hot cup of.....nevermind.
ok, tech: did you do anything to weather tight the holes drilled for wiring, like use some rtv to fill holes & keep wires from chaffing on the edge of the drilled metal?
now you get the option of driving by the speedo or tach again. My dash lights won't come on, nor will the volt meter gauge work., maybe it needs a hot cup of.....nevermind.
ok, tech: did you do anything to weather tight the holes drilled for wiring, like use some rtv to fill holes & keep wires from chaffing on the edge of the drilled metal?
Thread Starter
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Joined: Oct 2000
Posts: 2,572
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From: Longview, Tx
Originally posted by Project: 85 2.8 bird
and who says procrastination doesn't pay
now you get the option of driving by the speedo or tach again. My dash lights won't come on, nor will the volt meter gauge work., maybe it needs a hot cup of.....nevermind.
ok, tech: did you do anything to weather tight the holes drilled for wiring, like use some rtv to fill holes & keep wires from chaffing on the edge of the drilled metal?
and who says procrastination doesn't pay
now you get the option of driving by the speedo or tach again. My dash lights won't come on, nor will the volt meter gauge work., maybe it needs a hot cup of.....nevermind.
ok, tech: did you do anything to weather tight the holes drilled for wiring, like use some rtv to fill holes & keep wires from chaffing on the edge of the drilled metal?
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Joined: Mar 2000
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From: Central NJ, USA
Car: 1986 Firebird
Engine: 2.8 V6
Transmission: 700R4
Congrats on the diagnosis/fix! Sounds like exactly the same thing a GM technician would've done! Well, maybe, except for drilling a hole thru the floor. 
But why waste time tracing a short when you can just run a new wire? They don't want to hand a customer a bill for 5 hours of service; the customer would throw a fit... so it's easier/faster to run a new wire in a 1/2 hour.
But why waste time tracing a short when you can just run a new wire? They don't want to hand a customer a bill for 5 hours of service; the customer would throw a fit... so it's easier/faster to run a new wire in a 1/2 hour. 
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