Pcm Code E042, Left Oxygen (O2) Sensor Lean Signal: Action

PCM turns on SERVICE ENGINE SOON light. PCM turns on canister purge solenoid.

1. With O2 sensor disconnected, parameter ED32 should remain at reference voltage (.38-.63 volt).
2. Checks for sensor circuitry ability to record rich readings. DVOM set on volts will provide a small current source to drive circuit No. 1589 to greater than .64 volt (rich). Similar results may be obtained by placing a finger on battery positive terminal and another finger on O2 sensor circuit No. 1589 harness terminal.
3. PCM compares O2 sensor signal voltage received on circuit No. 1589 to ground voltage on circuit No. 413. If PCM does not have a good ground to engine on circuit No. 413, O2 sensor can appear falsely high or low. With engine running, use a voltmeter to measure voltage drop between O2 sensor at exhaust manifold and PCM terminal B6. If voltage is -.05 to +.05 volt, ground is okay. If voltage is less than -.05 volt or greater than +.05 volt, repair poor ground on circuit No. 413 between PCM terminal B6 and ground.