Join Date: Jul 2011
Location: Saint Petersburg Florida USA
Vehicle: 2003 SLK320 "Slinky"
Other Toys: 1990 VW Camper (Subaru-Vanagon), 1951 MGTD, 2012 Toyota Camry, 2004 Fleetwood Fiesta RV
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Thank you Savcom for your detailed response. I found it very helpful!
So since I didn't have a probe small enough to probe the Speed Sensor (SS) pins on N47-5 connector I measured across the appropriate pins on the N47-5 board assembly. With power off I measured roughly 42K ohm on the left rear (pin 6/7) and right rear (35/36). I went ahead and measured the left front (3/4) and right front (32/33) Both measured roughly 48K ohm. I removed the connector and remeasured and got slightly higher readings 43K ohm = rear, 52K ohm. These readings are due to the internal source resistance of the board assembly. The readings should all have been 1K ohm with the connector attached. This shows that all of the speed sensors are "open" and need to be replaced. I am of the belief that when powered in operation 12V is applied to the speed sensors so it makes me think that they all failed due to age unless my 12V supply was hit by Lightning. I removed one of the front SS connectors and measured 0.7M ohm across indicating it is essentially "open". So now I have 4 bad speed sensors, not 2!
I checked and verified 12V (constant) supply to N47-5 Pins 45/47 +12V, and pins 44/46 V-.
I checked Pin 18 for 12V (traction control) which measured 0VDC.
The ESP switch on the dash appears "dead" and does not light up or provide power to N47-5, pin 18.
It appears that K40 Relay K5 is not engaging. K40, F1 is good and has 12V.
There is no DC voltage on the Speed Sensor contacts with the car running and N47-5 connector attached.
N47-5 has constant power being supplied but appears to be in a "stand by' awaiting one or more inputs.
I guess I need to find out why the traction control relay (K40 K5) isn't engaging!
Yesterday I found a schematics of the Braking system including N47-5
I also previously had schematics from troubleshooting the engine control electronics which includes K40 and ME/SFI assemblies.
So... if anyone has a suggestion on what might be preventing N47-5 from turning-on I am all ears!
Also I'd like to figure out why all 4 of my speed sensors are "pushing up dasies"