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Cadillac Repair/2002 SLS Caddy Digi Speedometer

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Expert: - 2/1/2011


Question
I will ask differently.  My 2002 SLS digi speedo went dead after replacing front brake pads. Odd coincidence?
I had replaced the magnetic VSS and yesterday, for kicks, checked the old one on an ohm tester.  It seems to be good and I assume the new one is also good.  I need to check the circuits that feed from VSS to the PCM or Speedo head.. and from the PCM to the Speedo head... I do not know the circuitry so I need to know what to check and where. I had noticed that you or another expert had provided another questioner a list of info and pictures/charts of, and how to test, the system for troubleshooting.  Also, I had checked all the connections to all wheels.  Should I check the rear wheel speed sensors for ohm reading too??

Please help !
Without the speedo working, the car now shifts rough, not on cue and also when shifting from forward to reverse (or vica versa) I get a hard thud.  This all started same time that speedo went "dead".
Rick

Answer
Hi,

I rejected your question not because I did not want to answer it, it is just the question is way out of my expertise to answer.

Here is what I do when I need answers to something I am having issues with. I go to http://www.alldata.com This is where you can get the factory service manual down loaded for your specific car. It has the diagnostic flow charts and everything you need to fix this problem for good.

You sound mechanically proficient. This will give you the answers to your current problem I can't. There is a cost however. The fee is around $30 for the first car you download and $15 for any additional cars. The download is good for a year. You can print anything you need.

I have many occasions I need this information, so I buy what I need at the time. This is not Chilton, Haynes or Motors. I like it better that Mitchell. This is the un-edited factory service manual.

Good luck!

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Rob Painter

Expertise

Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?

Experience

Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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