PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

HELP!!!Everything works, except speedo after engine swap.

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Old Aug 1, 2010 | 05:34 PM
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Default HELP!!!Everything works, except speedo after engine swap.

So i just searched and searched this place and have come up with no luck. I just swapped a new motor into my car this weekend, and got it running today. All the guages work except the Speedo. The sensors are all plugged in to the trans (M6) and to the wheels. Ive unplugged the PCM and replugged, checked connections etc... its driving me mad! I have a scan tool and it is not reading any vehical speed. I turned my vss MIL to first error report and havent gotten a service light. Ive driven a few miles and its not working still.

Any ideas would be awesome. Thanks!

Last edited by live2dew; Aug 4, 2010 at 09:08 PM. Reason: PROBLEM FIXED. Thanks connexion2005
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Old Aug 1, 2010 | 07:10 PM
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Did you mess with the tune at all? IE OS swap or anything?

You can also check for power at the switch.
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Old Aug 1, 2010 | 07:21 PM
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no messing with the tune besides making it error report on the first fault. I have had no SES light/ error shown for VSS. I have no speed reading on my handheld code reader. All i did was unplug 3 connections (2 @ Front wheels and 1 @ at the trans) When i gave power back to the body etc and keyed up for the first time, my Tach and Speedo jumped and returned to zero. All others work as usual. I pulled the VSS from the trans after i test drove, checked for power... everything seems to be as it should. Just no signal at the dash.
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Old Aug 1, 2010 | 08:00 PM
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Make sure all the engine and pcm harness grounds are reconnected.
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Old Aug 2, 2010 | 09:11 PM
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checked all ECM and Engine grounds. Replaced fuses to guages etc. I probed B50, which is the VSS in the red connector and i am showing damn near battery voltage. Took guage cluster out and reinstalled to make sure it was making connection. Unplugged battery with key on, reinstalled...no luck. Unplugged battery for 30 min with key off, no luck. Unplugged 2 passenger kick panel connectors, reconnected and no luck. Speedo does sweep after guage cluster removal installation, so i assume its not the cluster....but it IS turning into a cluster F*** WTF? HELP please?!?
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Old Aug 4, 2010 | 09:07 PM
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So for anyone who wants may stumble on this thread with a similar problem.
Thanks to connexion2005 for the very informed answer to my problem.

20
LT GRN/BLK

Vehicle Speed Sensor (VSS) Reference Low

21
PPL/WHT

Vehicle Speed Sensor (VSS) Signal


In the red C2 connector that goes to the PCM, cut those wires and connect new wires (that you know are good) to the VSS pigtail. Bypass the factory wires that run back to the trans at the main harness. Aparently these wires have burned, got crushed or failed on a few cars. This gets you new wiring on the OUT side of the circuit. If this does not work, you obviously have a problem on the other side.
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