Faults and diagnostics

Start from what you have. If the unit reports a fault code, look the code up. If it does not, work from the symptom.

You have Go to
A fault code to look up Fault codes
A fault code and no idea what to do about it Fault diagnostics
A symptom but no code Troubleshooting
No communication, or a bus problem CAN bus diagnostics
Adaptation settings lost after ignition off Adaptation loss on shutdown
A known condition rather than a fault Advisories

Those pages document the current firmware. The diagnostic reasoning applies to 1.x units too — the wiring faults, sensor failures and bus problems are the same, and so are the checks. What can differ is the numbering and wording of individual codes.

Where 1.x differs

  • Code numbers and text may not match the tables on Fault codes. Use the description your unit reports to find the equivalent condition rather than matching the number exactly.
  • Faults are not stored across power cycles. Read them in the same power session as the problem. A fault that disappeared when you cycled the ignition is gone, not fixed.
  • Some conditions are protected in hardware without reporting a code. Output short-circuit protection acts whether or not anything is logged, so an output that has gone quiet is not necessarily fault-free.

If a code on your unit does not correspond to anything in the tables, send the code and its text to contact@apex-control.com with your serial number and firmware version.

The checks worth doing first

Most units that arrive for repair have a fault outside the unit. Before suspecting the controller:

  1. Supply and ground. Measure at the connector, with the engine cranking if the fault appears then. A voltage drop under load explains a surprising number of intermittent faults.
  2. The connector itself. Backed-out terminals, corrosion and a partially seated connector all present as an electronic fault.
  3. The bus. Termination, wire pairing and shorts — CAN bus diagnostics covers this with a multimeter, before you need anything more expensive.
  4. One sensor at a time. An input reading a fixed or implausible value points at that circuit, not at the controller.

When it is the unit

An input stuck at a fixed value, an output that never actuates, or a bus that is dead while the other works — those point at the hardware. Damage to input protection and output stages is repairable: Repair and service.

Where to go next