romeo_f

I have a 992 EM1 and I currently have the CEL on with code 17, I already researched and my connector pins seem in good condition and fuse 15 is perfectly fine, I just wanted to know how to check the sensor itself with a multimeter to see if it's working before I go and pay $100 for a new one..

Thanks

Former User

At the unplugged VSS connector with the key in ON(II), does the Blk/Yel wire terminal have battery voltage to body ground? Does the Blk ground wire have continuity to body ground? With the key off, does the Blu/Wht wire have a short (continuity to body ground)?

BryanM.

iTrader: (1)

I chased my tail for hours once trying to figure out why a VSS wasn't giving a signal.

Turned out all i had to do was clean the terminals (both the connector and the sensor).

I didn't bother to do it at first because they appeared clean and shiny. Go figure.

romeo_f

Thanks Ron let me check that and i'll get back to you, and Bryan, with what did you clean your terminals?

romeo_f

Ron, I just did the tests you told me and they were all positive, is there a way to test the sensor itself with the multimeter with me manually moving the gear on the sensor and expect some kind of signal?

BryanM.

iTrader: (1)

I used a VERY small, thin and fine needle file and some alcohol and lightly scrubbed them.

example because I'm bored

Former User

Are you saying that this test...

...yielded continuity to body ground? If so, the problem is a short in the Blu/Wht wire.

romeo_f

Ron I gave you the wrong info, I just re-did the test and here's how it goes:


The blk/yel wire DOES show voltage to the ground and the blk ground wire does NOT have continuity to body ground..


The Blu/wht DOES NOT show continuity to body ground..


Please let me know your comments and suggestions..

Former User

This is the problem. The ground is bad. You might want to do the test a few times to verify. I assume you did the test on the blk wire terminal in the VSS wire-harness connector. If it's verified to be bad, the problem could be the VSS connector terminal or the blk wire itself. Start by breaking through the blk wire insulation distant from the connector to see whether the result changes.

romeo_f

Thanks Ron, look I just did a test alone for the black wire in the harness, I left my multimeter connected to the ground in the harness and to the chassis when the key was in on position and nothing happened (no continuity), as soon as I turned off my key the multimeter began beeping detecting continuity. So the ground is working indeed, it's just NOT working when in ON position..

Former User

Was the VSS connector unplugged from the VSS when you did the test?

romeo_f

Yes sir..

Former User

The multimeter produces a small reference voltage to make resistance measurements. If the key is on, there is always a chance that voltage in the system will interfere with a resistance/continuity measurement. Using a basic physics analogy, it's like when two opposing forces neutralize one another. So whenever you do resistance/continuity measurements, you need the key off or in some cases the battery disconnected.

Given that having the key on interfered with your continuity measurement of the blk wire, you should also repeat the continuity to body ground test on the Blu/Wht wire with the key off to ensure that you did not similarly miss a potential short in that circuit. Also unplug the VSS connector for that test.

romeo_f

Thanks for you help Ron, it turns out it was indeed the VSS sensor that was fried, I managed to borrow a VSS from some friend and the speedo began to work perfectly.