P2689: Fuel Supply Heater Control Circuit High
Standardized SAE J2012 code · P26xx — Computer and output circuits
What does P2689 mean?
Voltage on the fuel supply heater control line is above the expected window. The fuel supply heater warms diesel at the filter or in the supply line so that paraffin crystals cannot clog the filter in cold weather; on GM diesels the engine control module switches it through a relay and checks the relay's low-side driver. If the heater does not work, the engine may be hard to start, lose power or stall in severe cold.
The code tells you which monitor failed, not which part is broken. Test before replacing parts.
Symptoms
- Hard starting, loss of power or stalling in severe cold
- Check engine light on
Common causes
- High Control wire shorted to B+
- Medium Open relay coil
- Low Connector pins corroded - high contact resistance
Likelihood is a general estimate across vehicles; your make and model may differ.
Add your car to see reports of P2689 on the same make and model first.
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