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Home >> Mercedes Benz >> 2001 >> ML320 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1453: Air Pump Relay >> Testing Procedure
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Testing Procedure

  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 "E" 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, test is complete. 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.
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