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Home >> Mercedes Benz >> 2001 >> ML430 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0136: Right O2 Sensor Downstream TWC (G3/6) >> Testing Procedure
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Testing Procedure

  1. O2 Signal -  Connect DVOM between ME-SFI control module connector "D" terminals No. 7 and 8 (socket box terminals No. 39 and 40). Start engine and idle. Keep engine speed between 2000-3000 RPM for approximately 2 minutes after engine coolant temperature reaches more than 176°F (80°C). Allow engine to idle. Voltage must exceed or drop to less than 450-500 millivolts within one minute. If voltage is okay, go to next step. If voltage is not okay, possible causes are right O2 sensor (after TWC) heater failure, wiring harness failure, defective right O2 sensor (after TWC - G3/6) or defective ME-SFI control module (N3/10). To check right O2 sensor (after TWC) heater failure, go to DTC P0141: O2 SENSOR HEATING OF RIGHT O2 SENSOR DOWNSTREAM TWC (G3/6)  .
    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 40 millivolts within one minute. 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 40 millivolts within one minute. If air pump responds and voltage changes, test is complete. If air pump does not respond or voltage does not change, possible causes are right O2 sensor (after TWC) heater failure, wiring harness failure, defective right O2 sensor (after TWC - G3/6) or defective ME-SFI control module (N3/10). To check right O2 sensor (after TWC) heater failure, go to DTC P0141: O2 SENSOR HEATING OF RIGHT O2 SENSOR DOWNSTREAM TWC (G3/6)  .
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