P2689: Fuel Supply Heater Control Circuit High

P2689 is logged when the fuel heater control line stays high even though the controller has commanded it on, so the relay coil is fed from battery positive and cannot be pulled in; the heater never works. GM's diesel ECM checks the low-side driver in its on state and treats 0.5 ohm or less to power as a short; the 2020 table uses 10 of 20 samples at 100 ms and Type C without lamp or message, while the 2014 table sets it as Type B. Ford's 2015 and 2016 diesel summaries give the code two jobs on the 3.2 L Transit: a vaporizer glow plug line held in the 10.9–12.32 V band for 5 s, and a relay status that contradicts the request for about 60 s, marked as provisional. In 2017 Ford split those into P269E and P26A0. Cold-weather starting is the main thing at risk.

Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

Symptoms

No fuel heating, gelling risk below freezing
Hard cold starts and rough idle until warm
Warning lamp only on some model years

Most likely causes

Control wire shorted to a battery-fed wire
Heater relay sticking so feedback no longer matches the command
Low-side driver in the engine controller defective

What to check, in order

Start with the simplest. You can tick off each step.

Check the connector and wiring
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Use live data to compare the reading with actual conditions
Measure power, ground, and signal
Replace the sensor if the circuit is good

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P2689 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
6: Control modules and outputs
89: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2689?

You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.

What causes code P2689?

The most common causes are: control wire shorted to a battery-fed wire; heater relay sticking so feedback no longer matches the command; low-side driver in the engine controller defective.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.