Check Engine Light On? We Come to You.
Flat $80 mobile OBD2 diagnostic scan at your driveway across Perth. P0420, misfires, sensor faults — diagnosed and fixed on-site. $0 call-out fee.
What's Included in the $80 Diagnostic
One flat fee. No hidden extras. If you proceed with the repair on the same visit, the diagnostic fee is credited toward the job.
Full ECU fault code extraction
All stored and pending DTCs read from every module — engine, transmission, ABS, airbag, and emissions.
Live sensor data analysis
Real-time O2 sensor readings, MAF values, fuel trims, coolant temp, and misfire counters reviewed while the engine runs.
Visual under-bonnet inspection
Physical check of vacuum lines, wiring harnesses, exhaust connections, and visible components related to the fault.
Written repair roadmap
You receive a clear, prioritised list of what needs fixing, what can wait, and a transparent parts-and-labour estimate.
Fault code clearing
Codes cleared after diagnosis so you can confirm the repair was successful and the light stays off.
Same-visit repair (if applicable)
Many faults — sensors, spark plugs, minor vacuum leaks — can be repaired on the same visit. Diagnostic fee credited.
P0420 — Catalyst System Efficiency Below Threshold
P0420 is one of the most common check engine light codes in Perth. It means your car's Engine Control Unit has detected that the catalytic converter is not converting exhaust gases (hydrocarbons, carbon monoxide, and nitrogen oxides) as efficiently as it should.
Common causes of P0420
- Failing or worn-out catalytic converter
- Faulty downstream (post-cat) oxygen sensor
- Faulty upstream (pre-cat) oxygen sensor
- Exhaust leak before or after the catalytic converter
- Engine misfire that has overheated the cat
- Oil or coolant burning through a worn engine
- Incorrect fuel type or contaminated fuel
Why diagnosis before replacement matters
A catalytic converter replacement costs $600–$1,800+ depending on the vehicle. But P0420 is frequently caused by a faulty oxygen sensor ($120–$250) or an exhaust leak ($80–$200) — not the cat itself.
Autova performs a full live-data analysis — comparing upstream and downstream O2 sensor waveforms, checking for exhaust leaks, and reviewing fuel trim data — before recommending any repair. We won't quote you a new cat if a sensor is the real cause.
Diagnostic: $80 flat. Credited toward repair if done same visit.
How Autova diagnoses P0420
- 1Scan all modules and record every stored and pending DTC.
- 2Review live O2 sensor data — upstream sensor should switch rapidly; downstream should be relatively stable. If downstream is switching rapidly, the cat is failing.
- 3Check for exhaust leaks between the engine and the downstream O2 sensor — a leak can cause false P0420 readings.
- 4Review short-term and long-term fuel trims for signs of a lean/rich condition that could be damaging the cat.
- 5Inspect spark plugs and ignition coils for misfires that may have overheated the catalytic converter.
- 6Provide a written diagnosis with root cause confirmed before quoting any repair.
Other Common Check Engine Light Codes
Autova diagnoses all OBD2 fault codes across petrol and diesel vehicles.
Severity is a general guide only. A flashing check engine light always indicates a high-severity active fault — pull over safely and call us.
Mobile Check Engine Light Diagnostic Across Perth
We come to your driveway, carpark, or workplace — no towing required.
Frequently Asked Questions
Everything you need to know about check engine light diagnostics in Perth.
Check engine light on? Let's sort it today.
Flat $80 mobile OBD2 diagnostic at your driveway. Same-day available across Perth southern suburbs.