Identify your unit

Two numbers identify a GCU: the serial number stamped on the case, and the firmware version it is running. Between them they tell you what the unit can do and what can be done to it.

The serial number

The serial is stamped on the unit, and it is not an arbitrary number. It reads as prefix · year · batch · unit:

GCU  22  02  001
│    │   │   └── unit number within the batch
│    │   └────── batch number
│    └────────── year of manufacture (2022)
└─────────────── product prefix

The same scheme is used across the range — GCU, IOC and DCU prefixes all follow it. Quote the serial in full; the prefix is part of it.

What changes between batches

The hardware was revised between batches. Two things move, and they are what decide whether a given unit needs work before it runs current firmware:

Axis Why it matters
Current sensing Determines which output types a unit can drive closed-loop, and how it must be calibrated
Output switch type Low-side on some batches, push-pull (low and high side) on others — this changes what you can wire to a PWM output

The output switch difference is already visible in the controller pinout: PWM outputs are "either low side or push pull depending on hardware version".

The batch-to-variant mapping is not published yet. Send your serial and you will get a straight answer for your unit — which variants it has, and whether it needs anything doing before a firmware update.

Some serial ranges also have known service items associated with them — Repair and service if you want a unit checked.

The firmware version

The version is reported by the configuration software when it connects to the unit. If you cannot connect, the version is not readable from the outside — send the serial number instead and it can be looked up.

Versions in the 1.x range are the legacy line. See Firmware and software.

What the version tells you

  • Which transmissions are supported. Support was added over time, so an older version may simply not contain the driver for your transmission.
  • Which torque calculation methods you have. The torque model was rebuilt more than once across the 1.x series.
  • Whether your configuration will transfer. A configuration written before 1.1 does not load on 1.1.1 or later.

Release history — legacy 1.x has the changelog for every version. Feature → minimum firmware works the other way round: pick the capability, see the version it needs.

Buying a used unit

Four things worth establishing before money changes hands:

  1. The serial number, so the hardware revision is known.
  2. The firmware version, so you know what it supports.
  3. Which transmission it was configured for. A configuration is specific to a transmission and does not transfer.
  4. Whether it has ever been repaired, and for what.

A unit of unknown history is worth putting through a full hardware test before it goes into a car. That is cheaper than finding a damaged input during commissioning.

What to send when asking for help

The serial number, the firmware version, the transmission, the vehicle, and the engine control unit it talks to. With those five, most questions can be answered in one reply. Email contact@apex-control.com.

Where to go next