Dess switch and cap programing

[Burro]

Can I buy a new dess switch and cap pre programmed . Do I have to involve a dealer ?

 

[Coastiejoe]

The cap does NOT need to be programed. Just the lanyard/key.

 

[Burro]

I'm getting no tones or diagnostic codes have any ideas ?

 

[Coastiejoe]

I'm getting no tones or diagnostic codes have any ideas ?

Is the engine cranking, starting, or nothing.

Here is how to test the DESS.

1. Solid black wire is a dedicated ground
2. Black wire w/yellow tracer is the return path to ground for the MPEM that supplies ground back to the DESS portion of the module
3. White wire w/grey tracer is your Maxim protocol one wire low voltage communication circuit to the module that allows the protocol to execute the function of slave / master from both the module DESS feature and 64 bit security code stored in the Dallas Semiconductor IC chip in the lanyard cap.


The DESS post is a reed switch, your lanyard contains a magnet and when placed on the post it completes the circuit between the solid black and black w/yellow trace. The presence of a ground back to the module on the Blk/Ylw allows the module to read the code stored in the lanyards ROM chip that is pre-programmed to the MPEM memory. When it recognises the security code it unlocks the ignition circuit and pulses the beeper to give you a thumbs up.

To test the post, unplug it and remove it to your bench it's easier to probe everything that way. You should have continuity from the solid black wire to the metal ring on the outside shoulder of the post all the time. You should also have continuity from the white w/grey trace wire to the small contact on the very top center of the post all the time.

With the key off the post, you should have no continuity between the black and black w/yellow wires, with the key placed on the post that should complete the circuit and show continuity between them with little to no resistance.

There are a few things you can do to test the key itself, clean it first with a q-tip dipped in alcohol and make sure the two side and one top contacts are in place and clean.

You should see continuity between both of the ground contacts in the side body of the key, and using the red test lead on either of the side ground contacts and the black test lead on the top center contact you should see less than 10 ohms of resistance on the IC serial chip.

I find any more than 10 ohms on the IC chip usually causes intermittent or complete failure of the key to work properly with a MPEM module, my shop version of Candoo Pro will read keys up to about 20 ohms of resistance and program them to modules every time but the MPEM won't recognise them reliably in normal operation.