Car Repair And Service

rustbuster

In a recent diagnostic session on a moderately modern vehicle (circa 2015–2017), I encountered intermittent fault codes related to the oxygen sensor (P0135/P0136) accompanied by a transient lean condition (P0171). The issue does not present under static conditions, and preliminary tests of the wiring harness and connectors revealed no visible anomalies. Given that fuel pressure and injector performance remain within specification, I suspect that the problem might be associated either with a marginal sensor output or a wiring fault that manifests only under dynamic load.

I am considering employing an oscilloscope to capture live sensor voltage data over varying engine loads and temperatures to correlate transient deviations with the fault occurrences. Has anyone with experience in advanced diagnostics for intermittent sensor faults in ECU-controlled systems utilized a similar method? Specifically, I am interested in detailed procedures for synchronizing oscilloscope traces with real-time ECU logs, and any suggestions for confirming whether the issue is sensor-related or indicative of a subtle wiring degradation that only becomes apparent under certain operational conditions.

Any technical insights, recommended diagnostic tools, or alternative strategies for isolating such intermittent faults would be appreciated.

GarageGoose

Sounds like you’re on the right track. In my experience, synchronizing scope data with ECU logs works best when you trigger the scope on a specific event code. You might consider using a data logger that timestamps the readings to align with the ECU’s output—I’ve seen that approach help pinpoint if it’s a sensor output fluctuation or a wiring resistance issue during transient loads. Also, a bench test of the sensor under simulated engine conditions might add some clarity.