Action Taken
ECM turns on "Engine Control System Fault" telltale. ECM enables canister purge. ECM uses right oxygen sensor information for fuel control unless codes EO13, EO44, or EO45 are set.
NOTE:
The following step numbers refer to circled numbers on diagnostic chart. See Fig 1
. For circuit identification, see Figure
.
- With the oxygen sensor disconnected, parameter ED32 should remain at reference voltage (0.38 to 0.63 volts).
- Checking for sensor circuitry able to record rich readings. The DVOM set on volts will supply a very small current source to drive CKT 412 above 0.64 volts (rich). Similar results may be obtained by placing one finger on battery positive and another finger on oxygen sensor CKT 412 harness terminal.
- The ECM compares oxygen sensor signal voltage received on circuit 412 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 B6. If the voltage is greater than -0.05 to +0.05 volts, repair poor ground on CKT 413 between ECM terminal P4 and engine ground.