Speedo Problems

**ChrisJ** · 06-23-2009

I have been having some issues after my header install with my speedometer. About a week after installing them the speedometer started jumping around. I swapped out the speed sensor worked for a few days then started acting up again. Last weekend I pulled the entire harness out for the speed sensor on the trans. Looked it all over wiped all the wiring down, cleaned all the connections. It was good to go for about a week.

This weekend it started acting up again. It doesn't have a pattern to when it decides to act up. It will jump up and read fine then fall off totally. The trans is feeling fine other then not knowing when to downshift. No metal shavings on the sensor. Car only has 50k on it.

Anyone have any ideas? Need to get it though inspection this month

Thanks.

**Trannyman95** · 06-23-2009

Do the wires look ok inside of the wire loom? I have heard of a number of guys having this problem and it was from the wires melting because they were too close to the header tubes. There are a few other scenarios but since this happened after the header install I would definately rule that out first. A scope would verify proper VSS operation while driving down the road to test the sensor itself but most guys dont have equipment like this to test with. A scan tool will also show VSS as mph but is likely going to match what your speedo is doing. I would take a closer look at the harness and pull the loom off and see what the speed sensor wires look like. Also you should use an ohm meter and test between the VSS connector and the PCM connector to make sure there isnt a break in the wire. With an ohm meter hooked up on each end of the wire you can wiggle the harness and watch for an open

**ChrisJ** · 06-23-2009

Yes. I have hooked HPTuners/Scanner up to it and it shows a MPH reading when the car is moving just fine. Though that but not the Speedometer. All the wiring under the loom looked fine. I will look into doing a look at it with an ohm meter.

**ChrisJ** · 06-29-2009

I tested from the plug to where the wiring goes into the main loom, under the MAP sensor. All of that tested good. I didn't test from there back to the PCM. I really doubt its in there. I need to pull it out and look at it. Could the plug that snaps onto the speed senor be bad? It all looks good and snaps in firmly.

Could the speedo head in the dash be bad?

Any ideas?

**Trannyman95** · 06-30-2009

Since you can watch HPT scanner while you drive does the speedometer on the scanner read steady the entire time while the one in the dash drops out? It is coming off of the same sensor and they are both data stream signals. Have you tried to use cruise control while this happens and if is will it stay locked in ok or does it kick out when you see the speedo act up? I wouldnt suspect the connector to be bad if it reads good on the scanner, but if the scanner matches what the speedo in the car is doing then you should dig further into the connector and wiring.

**ChrisJ** · 06-30-2009

The scanner is not matching what the gauge is doing. Scanner is steady, gauge is all over the place. Is it possible the gauge pod or pcm went out?

**ChrisJ** · 06-30-2009

Also I went though it earlier tonight tested from connector all the way to PCM. The wiring carries a current tested it with a meter.

**Trannyman95** · 06-30-2009

I would suspect your cluster is going bad then. The speedo signal is referrenced from the VSS in the trans and since it reads fine on your scanner then you are left with wiring from the underhood junctions into the car or the cluster itself.

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