Case Study: P2404 - - EVAP Leak Detection Pump Sense Circuit: Implausible Signal

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Jef

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The subject:
2006 A4 with 2.0 BPG engine

The victum:
Chad Z who hails from beautiful downtown North Ridgeville, OH... Cleveland Magazine's June 2002 pick for "best festival in Northeast Ohio"!!!!

2006 A4, keeps flagging the P2404 - - EVAP Leak Detection Pump Sense Circuit: Implausible Signal. Prior to calling, Chaz had ohm tested the LDP (V144):

/1 + /3 = 680Ω
/2 + /3 = 16Ω

These values are to factory design. Loaded tested voltage on wiring harness with light bulb on wiring harness /3, carries load, no signs of voltage drop.

Go to do Basic Settings 071, fuel tank has 1/4 tank. Test fails within 10 seconds, very fast for a failure. I request Chad check for vacuum supply to the LDP (V144) with the engine at idle. No vacuum.

Look in engine bay for a vacuum check valve and nipple, close to brake booster... and this is found:


Photo credit to Chad Z, Hasselblad H6D-400c MS 1/850 @ f5.6

Well, that sucks... or rather not at the LDP (V144). :o
 
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Jef

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2010 Tiguan with a 2.0T CCTA engine. Same P2404 fault code. LDP been replaced, wiring looked over, just can't find anything wrong with it.

Do you have engine vacuum at the LDP? .... eh... no, I don't. Back in the engine bay, found vacuum line disconnected. Hooked it up, vacuum at LDP now.
 
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