I Can’t Believe This ECU Driver Survived... (O2 Heater Circuit Testing)

A downstream O2 heater code is easy to ignore — until you see 20+ amps of current on the circuit.
In this video, I capture a spike that could have destroyed the ECU driver and explain why voltage testing alone can miss it. The vehicle being worked on is a 2016 Mini Countryman 1.6L Turbo.

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We walk through proper O2 heater circuit testing and show why voltage checks alone can be misleading on PWM-controlled circuits. We break down how heater power is supplied, how the ECU controls the ground side, and why current testing is critical when you want to protect computer drivers.

This isn’t about guessing or throwing a sensor at a code.
It’s about understanding how the circuit works, so you don’t miss a failure that can damage an engine computer.

CHAPTERS
00:00 – O2 Heater Current Spike (ECU Driver Survives)
00:46 – Vehicle Background + Why This “Simple” Code Matters
02:25 – Heater Circuit Strategy (Power, Ground, Control)
03:43 – Wiring Diagram Breakdown (Terminal 87 + Driver Control)
07:00 – Identifying Heater Wires at the Sensor
10:10 – KOEO Voltage Checks (Why 12 & 12 Makes Sense)
12:30 – Engine Running: PWM Control + Current Measurement
16:00 – Why a DMM Can Mislead You on PWM Circuits
18:15 – Code Behavior + Temperature-Based PWM Changes
23:20 – Massive O2 Heater Current Spike Captured
27:55 – Proving It’s Real (Not an Instrument Error)
34:05 – Why Ignoring Heater Codes Can Kill Drivers
36:30 – Final Verdict: Internal Heater Failure
37:30 – Wrap-Up + Training Resources

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⚠️ DISCLAIMER
ScannerDanner LLC is not responsible for misuse, unauthorized changes, or incorrect application of any information provided. Always follow proper safety protocols when using tools, equipment, or procedures discussed in this video. Use this content at your own risk.