Powertrain, generic (extended)

P2689 Fuel Supply Heater Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

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

Symptoms

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

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–350
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel supply heaterwiring harness

Related codes

P2687P2688P269EP26A0

References: gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com, fordservicecontent.com.