Key Position H0 (Auxiliary contact)

Ray Diagnostician Wichita, Kansas Posted   Latest  
Discussion
Electrical
2000 Mercedes-Benz C230 Kompressor 2.3L (111.975) 5-spd (722.6)
No Crank / No Start

Does anyone know what this is. I'm not getting a crank signal to the starter and I know it's because this stays at NO instead of yes.

So what is the "Key Position H0 (Auxiliary contact)" Where is it at?

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Alan Diagnostician
Glenrothes, United Kingdom
Alan Default
 

Could it be the transmission start inhibit circuit?

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Ray Diagnostician
Wichita, Kansas
Ray Default
 

Transmission is in Park/Neutral and scanner verified too

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Alan Diagnostician
Glenrothes, United Kingdom
Alan Default
 

Park position from gear selector shows on dash and scan tool, and cable between selector and Eis can allow key to turn to start position, however reed switch in transmission could still be in wrong place. With no fault codes. But if you’ve put car in neutral and pushed it and it’s definitely not stuck in gear. Then I guess its something else. Having star shows so much more than all after market…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Ray: I suggest looking it up in your User Guide. Different scan tools sometimes display different PIDs differently. Sometimes, a PID may just be a place holder. From the FWIW Dep't: I chased my tail almost 20 years ago with a PID on a Snappy product. After finally having someone get back to me on the phone, I was told that it really wasn't a valid PID being displayed even though the…

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Michael Technical Support Specialist
Milwaukee, Wisconsin
Michael Default
 

I would check that park-neutral switch in the trans, I just ran into something similar on a dodge challenger with the 722.6 in it, turns out that the switch was faulty and not letting the car start. no codes at all in any system.

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Ray Diagnostician
Wichita, Kansas
Ray Default
 

Verified on scanner gear position, moving between all gears back and forth and scanner switches respectively to each one as its supposed to

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Alan Diagnostician
Glenrothes, United Kingdom
Alan Default
 

The gear linkage falls off the shaft as it’s only held on with a flimsy c clip. The dash and scan tool will show gear position movement when you move the selector as that comes from the selector mechanism not the micro switch in side the box. Seen a few. Gear selector feels like normal. Dash shows park, scan tool shows park but cars actually stuck in gear. Even Mercedes scan tool just shows…

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Matthew Owner/Technician
North Bethesda, Maryland
Matthew Default
 

HO is position 1 ,like the old accessory position. What you need to look for is circuit 50, thats the cranking signal on a Mercedes. Key inserted is position 0, next detent is position 1=accesory, next detent position 2 =ignition on,, next is position 3 -cranking. hope this helps. Matt

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Ray Diagnostician
Wichita, Kansas
Ray Default
 

On the scanner, if you look through the pictures I posted the circuit 50 signal is activating and sending starting signal like it's supposed to. Per your theory that means "key is not inserted in position 0" because scanner is getting a NO signal even though everything else is changing values

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Matthew Owner/Technician
North Bethesda, Maryland
Matthew Default
 

Not a theory, when the key is out, or just inserted and not turned that is position zero or 0. Dont chase HO, follow circuit 50from ignition switch over can to front sam to starter. starter circuit 50 always purple on a mercedes. thanks Matt

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