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05 / TrueKeylessGPX

Engine diagnostics

ECU integration

Engine diagnostics is part of my TrueKeylessGPX work on the GPX: fault codes, live engine data and a configurable temperature warning in the service app.

TrueKeylessGPX enclosure with its connector harness laid out alongside it

From my workbench

Connected to the motorcycle

The TrueKeylessGPX control unit and wiring connections. Engine diagnostics is another function of this shared hardware platform.

What the ECU can tell me

The TrueKeylessGPX service app has a “Live Data” tab for engine information and diagnostic functions. It brings the ECU’s fault information and operating parameters into the same app used for the rest of the motorcycle system.

Fault codes

The documented functions include reading diagnostic trouble codes from the engine control unit and clearing its stored errors and Check Engine indication. A code is a starting point for investigation. Clearing an entry does not repair the condition that produced it.

On this page, I will add actual fault-code examples from my GPX together with what I checked and what the result was.

Live parameters

ParameterDisplay described in the manual
Battery voltageCurrent electrical supply reading
Vehicle speedCurrent speed
Engine temperatureTemperature reported by the system
Engine speedRPM
Throttle positionPercentage

An audible temperature warning

The system can warn the rider when engine temperature exceeds the configured threshold. The manual describes 150°C as the example threshold, with a two-tone warning repeated twenty times. The threshold is adjustable; its meaning depends on the engine and the temperature measurement used.

Keep the interfaces distinct

The stock cluster’s Check Engine indicator input appears in my 20-pin connector map. That lamp input is not itself the ECU diagnostic communication interface. The diagnostic connection, ECU identification and captures will be documented separately as I add the installation material.

The feature list here comes from the TrueKeylessGPX manual. It does not imply compatibility with every ECU or every GPX revision.

Operating details adapted from my TrueKeylessGPX user manual. The manual remains the reference for setup and operation.

Part of my GPX 250 Twin Brighton workshop journal.

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