Code Definition

P0689 — PCM Power Relay Control Circuit Low

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Holden

About P0689

P0689 is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Holden vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0689 is stored, the module has detected a signal or supply voltage lower than the expected operating range.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0689 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Powertrain Control Module (PCM) monitors its power relay control circuit to verify correct voltage and relay operation. DTC P0689 is logged when the PCM detects a voltage lower than the expected range on the control circuit while the relay is commanded on. This indicates the PCM cannot energise the relay properly due to a short to ground, high resistance, or an open circuit, which can interrupt power delivery to critical engine and transmission control circuits. Because the relay feeds the PCM and related systems, a low or open control circuit can cause a no start, stalling, or systems tha...

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