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Home >> Mercedes Benz >> 2002 >> ML320 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0410: Air Injection Malfunction (Functional Chain) >> Testing Procedure (Secondary Air Injection)

Testing Procedure (Secondary Air Injection)

  1. Actuation -  Connect DVOM between ME-SFI control module connector "C" terminal No. 28 (socket box terminal No. 20) and ME-SFI control module connector "A" terminal No. 2 (socket box terminal No. 2). Disconnect Engine Coolant Temperature (ECT) sensor connector. Connect a 2.5 k-ohm resistor to ECT sensor harness connector. Start engine and idle. Voltage should be 11-14 volts for approximately 2 minutes with air pump running. If voltage and air pump respond correctly, go to next step. If voltage and air pump do not respond correctly, possible causes are wiring harness failure, defective fuse or relay in fuse and relay module (K40), (F1) or defective ME-SFI control module (N3/10). Repair as necessary. On C class, CLK class and E class, fuse and relay module (K40) is located in right rear corner of engine compartment. On ML320, fuse and relay module (F1) is located in left rear corner of engine compartment.
  2. Current Consumption -  Ensure 2.5 k-ohm resistor is still connected to ECT sensor harness connector. Connect ammeter between ME-SFI control module connector "A" terminal No. 3 (socket box terminal No. 3) and ME-SFI control module connector "C" terminal No. 28 (socket box terminal No. 20). Turn engine off with ignition on. Amperage should be 0.1-0.3 amps. If amperage is within specification, go to Testing Procedure (Air Pump Switchover Valve - Y32) . If amperage is not within specification, possible causes are wiring harness failure, defective fuse or relay in fuse and relay module (K40), (F1) or defective ME-SFI control module (N3/10). Repair as necessary. On C class, CLK class and E class, fuse and relay module (K40) is located in right rear corner of engine compartment. On ML320, fuse and relay module (F1) is located in left rear corner of engine compartment.


  1. Functional Chain -  Connect DVOM between ME-SFI control module connector "C" terminal No. 31 (socket box terminal No. 23) and ME-SFI control module connector "C" terminal No. 32 (socket box terminal No. 24). Start engine and idle. Allow engine to idle for at least 2 minutes after engine coolant temperature reaches more than 176°F (80°C). Observe O2 sensor signal voltage before TWC. O2 sensor signal voltage should fluctuate between -.2 volts to one volt. If voltage is okay, go to next step. If voltage is not okay, possible causes are air pump switchover valve (Y32) defective, combination valve for secondary air injection defective or no output from air pump. Repair as necessary.
    NOTE: Manufacturer recommends using socket box for jumpering terminals in next step.
  2. Connect jumper wire between ME-SFI control module connector "A" terminal No. 3 (socket box terminal No. 3) and ME-SFI control module connector "E" terminal No. 10 (socket box terminal No. 66). Air pump should run and voltage should change to less than 100 millivolts within 20 seconds. Connect jumper wire between ME-SFI control module connector "A" terminal No. 3 (socket box terminal No. 3) and ME-SFI control module connector "C" terminal No. 28 (socket box terminal No. 20). Air pump should run and voltage should change to less than 100 millivolts within 20 seconds. If air pump responds and voltage changes, test is complete. If air pump does not respond or voltage does not change, possible causes are air pump switchover valve (Y32) defective, combination valve for secondary air injection defective or no output from air pump. Repair as necessary.
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