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Home >> Cadillac >> 1990 >> Allante F7/ME9 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> ECM DTC EO43: Left O2 Sensor Rich >> Action Taken

Action Taken

  1. ECM turns ON Service telltale.
  2. Canister purge is enabled.
NOTE: The following step numbers refer to circled numbers on diagnostic chart. See Fig 1 . For circuit identification, see Figure .
  1. With the oxygen sensor disconnected, parameter ED33 should remain at reference voltage (0.38 to 0.63 volts).
  2. Checking for sensor circuitry able to record lean readings.
  3. The ECM compares oxygen sensor signal voltage received on circuit 912 to the ground voltage on circuit 413. If the ground voltage on circuit 413 is not engine ground (battery negative), the oxygen sensor can appear falsely high or low. With the engine running, use a voltmeter to measure voltage from the oxygen sensor pin A to the ECM terminal E15. If the voltage is greater than -0.05 to +0.05 volts, repair poor ground on CKT 413 between ECM terminal E15 and engine ground.
Fig 1: Identifying ECM DTC EO43: Left O2 Sensor Rich Flow Chart
G00114225Courtesy of GENERAL MOTORS CORP.
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