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Home >> Mercedes Benz >> 2001 >> ML320 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0440: Purge System Leaking (Functional Chain) >> Testing Procedure
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Testing Procedure

  1. Vacuum Control -  Connect vacuum gauge at purge control valve (Y58/1) between purge line to activated charcoal canister. Start engine and idle until operating temperature is reached. With engine idling, vacuum gauge should indicate more than 5 mbar after approximately 2 minutes. Vacuum gauge should also fluctuate and purge control valve (Y58/1) must cycle in the process. If all conditions are okay, go to next step. If all conditions are not okay, possible causes are vacuum line(s) failure or purge control valve (Y58/1) defective. Repair as necessary.
  2. Leaktightness -  Connect jumper wire between ME-SFI control module connector "A" terminal No. 3 (socket box terminal No. 3) and ME-SFI control module connector "D" terminal No. 2 (socket box terminal No. 34). Disconnect purge control line to activated charcoal canister at purge control valve (Y58/1). Connect vacuum pump to purge control line. Turn ignition on. Apply approximately 25 mbar of vacuum to purge control line. Vacuum pump should indicate a less than 5 mbar pressure drop after approximately one minute. If pressure drop is okay, test is complete. If pressure drop is not okay, possible causes are fuel tank cap leaking, purge control line to activated charcoal canister leaking, purge control line from activated charcoal canister to activated charcoal canister shutoff valve (Y58/4) leaking, activated charcoal canister defective, activated charcoal canister shutoff valve (Y58/4) defective or purge control valve (Y58/1) defective. Repair as necessary.
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