P2687: fuel-filter heater open-circuit detection uses off-state feedback

P2687 identifies the open-circuit branch of the fuel-filter heater control diagnostic in this GM document. The controller evaluates the heater's low-side driver and sees a feedback pattern inconsistent with the connected load. The code does not establish that the fuel is too cold or that the filter is blocked.

The monitor is tied to driver state

The documented open-circuit pattern is low voltage while the driver is off. The table associates that with high impedance between the ECU pin and the load. The exact wiring arrangement still has to come from the applicable vehicle procedure; the summary is not a connector or pinout diagram.

A nearby short-to-ground diagnosis can also involve low off-state feedback. That is why command state, the specific driver fault classification and controlled circuit testing are more useful than treating any low reading as the same defect.

A startup snapshot may be outside the test window

Evaluation requires a sufficiently stable battery supply, an engine-speed threshold selected from a calibration table and an appropriate post-drive state. The published failure duration is two seconds, checked on a 0.2-second monitoring cycle when enabled.

Preserve those conditions alongside the code. The source provides no automatic instruction to replace a filter assembly or control module. A qualified technician should isolate the circuit using the correct fuel-system precautions and wiring procedure. Verify restored command/feedback behavior during a valid evaluation, rather than assuming a code clear confirms heater operation.

Source and applicability

GM 2015 15OBDG04 fuel-filter heater driver monitor. Only the cited monitor and calibration are described; per-code vehicle and engine applicability has not been established.

15OBDG04 Engine Diagnostics, physical PDF page 253.